Posts Tagged ‘strawberry’

Strawberry IPM Newsletter No. 5 – June 17, 2016

Friday, June 17th, 2016

StrawberriesStrawberry IPM Newsletter No. 5 – June 17, 2016
Click on photos to enlarge.

STRAWBERRY HARVEST BEGINS IN SOUTHERN MAINE

Watch for Birds, Slugs, Sap Beetles

Situation:
Strawberry harvest is underway in much of southern Maine, and should be into full swing next week. So far, the crop looks good. Very low pest pressure and good growing conditions, aside from a lack of water, have resulted in good fruit quality. Berry size may be a bit small, especially in fields that have not been irrigated. It’s time to keep an eye out for ripe fruit pests, including birds, sap beetles and slugs.

Strawberry bud weevil or “clipper” is no longer a threat in fields in the southern and mid-state regions. There may be a few fields in northern Maine that still have some susceptible flower buds on late blooming varieties, and those should continue to be scouted. A reminder: clippers will move on to raspberries and blackberries and clip off their buds once the strawberries have come into bloom.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Tarnished plant bug activity is still quite low in strawberry fields this week, with very few sites finding any nymphs, and no fields over the spray threshold. Northern fields should continue to be scouted for nymphs until the primary (king) berries begin to color.

Two-spotted spider mites are still prevalent in strawberry fields this week. Nearly all fields scouted had mites and four locations were over the 25% infestation spray threshold. If dry weather continues, mite build-ups will continue to be a problem. If infested fields are now being harvested, be sure to check miticide labels for re-entry and days to harvest restrictions, or delay sprays until harvest is over.

Sap beetle on strawberry

Picnic Beetle (left) on Strawberry, photo by James Dill

Sap beetles can become a problem in ripe fruit, especially in dry years. Growers should keep an eye out for damage as the berries start to ripen. The 1/8-inch long, dark brown beetles chew small holes in ripening fruit, similar to slug injury. They may be found in the holes they’ve chewed, but often drop to the ground when disturbed. The best management strategy for sap beetles is good sanitation. Keep the field free of overripe fruit by picking often and thoroughly. Insecticide sprays for this pest can be effective, but should be a last resort during the harvest period. Assail® Brigade®, Dibrom® and PyGanic® are registered for control of sap beetles with pre-harvest intervals ranging from 12 to 24 hours. Read the product label carefully for this and other application instructions and restrictions.

Birds, specifically cedar waxwings, will soon be moving into fields to feed on ripe fruit, if they haven’t already. These birds can destroy many of the early ripening fruit, despite our best efforts to scare them off. Only by keeping a near constant presence in the field and eliminating roosting sites can you reduce the damage. Songbirds are protected by law and should not be killed. However, permits may be issued for killing birds by the U.S. Fish and Wildlife Service if they receive a recommendation for such a permit from the Maine Wildlife Services Office (part of the USDA Animal and Plant Health Inspection Service) in Augusta, along with an application from the grower. There is a $50 fee for the application, and it may take over a month for the permit to be processed. However, the permit is good for one year, so if you have problems this season, you may consider applying for a permit this winter, which would allow you an option to kill birds, if necessary, next season. The Wildlife Damage Office has recommendations for managing birds in crops, and also has some control options available through their office. For more information on permits or bird control contact the office in Augusta at 207.629.5181. The office is located in the Capital West Business Center at 79 Leighton Road in Augusta.

Slugs may be a problem in some fields this season. Although they tend to be worse in wet springs, especially if they follow a wet fall. Moist conditions and thick mulch tend to encourage the presence of slugs. Slugs usually feed at night, leaving large holes and tunnels in ripening fruit. Baits such as Deadline® and Sluggo® offer some control of slugs, but should be used prior to fruit ripening. Pay close attention to label instructions and precautions. Baits should also be applied to the fields in mid-September if slugs have been a problem, to reduce egg laying.

Diseases: Fruit rot diseases have not been prevalent in fields now being harvested. Dry weather and timely fungicide applications appear to have keep fungal problems at bay. Fields that are still in flower may still need additional protection, should wet weather finally move in.

Strawberry Harvest

Strawberry Harvest, photo by David Handley

Annual Pre-Harvest Checklist for Pick-Your-Own

It’s that time again! As harvest approaches, its time to make sure that your farm is ready to provide your customers with the best possible picking experience. Take our annual review below to evaluate your customer readiness.

  • Your phone message and web/Facebook pages with picking conditions and opening and closing times are regularly updated.
  • Signs to the farm are neat and easy to read.
  • There is easy access to the fields and plenty of parking.
  • Someone is ready to greet customers and offer parking instructions and directions to the field.
  • Access to the field is free of hazards.
  • Transportation is provided for the elderly and disabled.
  • The rules regarding picking are clearly posted.
  • Someone is in the field to show customers where to pick and to answer questions.
  • There are plenty of picking containers available.
  • Clean restroom and hand washing facilities are available.
  • Someone is available to help customers carry fruit out of the field.
  • The checkouts are fast and efficient.
  • Beverages are available.
  • Shade and seats are available for customers wanting to rest.
  • The help are friendly and knowledgeable.

A friendly, clean, and organized atmosphere will leave a lasting impression on your customers, encouraging them to come back and to recommend your farm to their friends.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259         Orono, ME 04473
207.933.2100                          1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 1 – May 20, 2016

Friday, May 20th, 2016

StrawberriesStrawberry IPM Newsletter No. 1 – May 20, 2016
Click on photos to enlarge.

2016 STRAWBERRY PEST MANAGEMENT SEASON BEGINS

Long, Cold Winter Delays Early Spring Growth

Situation:
The winter was slow to get started, provided only intermittent snow cover and got very cold just before giving up. It has left some strawberry plantings with significant winter injury, while others seem to have come through in good shape. The distribution and degree of injury is like the winter, very variable from site to site; although it seems Maine growers may have actually experienced less damage than some of their southern New England counterparts. If winter injury is present, cutting into the crowns of injured plants will reveal dark brown discoloration in the internal tissue. Helping plantings recover from winter injury involves compensating for the damaged vascular system. Make sure the plants get plenty of water, especially in this dry period; and it may help to apply extra nutrients to encourage root growth and flower development, including nitrogen, calcium, and phosphorus. While we do not recommend heavy nitrogen fertilizer applications in the spring, up to 20 pounds of actual N (e.g. 125 lb. calcium nitrate) may improve early spring growth.

2015-2016 New England Small Fruit Management Guides are available at Highmoor Farm. The guide contains the latest information on management options for small fruit pests as well as cultural information. Cost of the guide is $13.00 plus $2.61 postage for a total of $15.61.

To order the guides, please send your check made payable to UMaine Cooperative Extension mailed to: Highmoor Farm, P.O. Box 179, Monmouth, Maine 04259, attention Pam St. Peter. For more information, contact Pam St. Peter at 933.2100 or pamela.stpeter@maine.edu.

We will begin scouting strawberry fields for major insect pests next week, including volunteer farms in North Berwick, Wells, Cape Elizabeth, Poland Spring, New Gloucester, Dresden, Monmouth, Wayne, and Farmington, and will be reporting our findings through this newsletter and blog on a weekly basis until harvest time. You can also get quick access to this information on the Pest Management web page at http://umaine.edu/ipm/.

The best way to manage strawberry pests is to scout your own fields regularly and often. You should start scouting regularly as soon as flower buds emerge from the crown. You should be able to identify the major pests and their damage, and be able to determine if control measures are necessary. To properly scout your fields you may want a copy of the Strawberry Production Guide for the Northeast, Midwest and Eastern Canada. This contains detailed information on strawberry pest identification and monitoring, and also provides information on all other aspects of strawberry production. It may be purchased for $45.00 per copy from the University of Maine Cooperative Extension Publications Catalog online.

Clipper Beetle on Strawberry Bud

Clipper Beetle on Strawberry Bud, photo by James Dill

Strawberry bud weevil or “clipper” are becoming active as flower buds begin to emerge. We have had reports of clipper activity within other New England states and in southern Maine. The clipper is a small weevil, which girdles strawberry flower buds, causing them to dry up and fall off the flower stalk. Scout for damage by counting the number of clipped buds in two feet of row length at five different locations in a field. If the average number of clipped buds per two-foot sample exceeds 1.2, or if live clippers are found, control measures are recommended. Damage is usually first noticed at the edges of the field. Border sprays may be effective in keeping this insect from becoming a problem in larger fields. Fields with a history of clipper problems will typically exceed threshold nearly every year. Insecticide options for clipper include Lorsban®, Brigade®, Sevin® and PyGanic®.

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, Photo by David Handley

Tarnished plant bugs adults will soon be laying eggs. Strawberries are one of their preferred hosts at this time of year. Once the eggs start to hatch, we’ll find the nymphs feeding in the flowers. The nymphs are small, active, yellow-green insects. It is important to scout for them regularly, as they can appear very quickly in warm weather. Tarnished plant bugs feed on the open strawberry flowers, causing the berries to have seedy ends. To scout for the nymphs shake 30 flower clusters (six clusters in five different locations) over a plate. If four or more of the clusters out of the 30 sampled have any nymphs, control measures should be taken. Be on the alert and scout your fields now! Insecticide options for tarnished plant bug include malathion, Brigade®, Danitol®, and PyGanic®.

Cyclamen Mite Damage on Strawberry Plant

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

Cyclamen mites: Plants showing weak growth and yellow, pinkish or blackened, crinkled leaves may be infested with cyclamen mite. Cyclamen mites are very small, smaller than spider mites, and reside in the crown of the strawberry plant feeding on the developing leaves and flower buds. They are very hard to see, even with magnification. Infested plants have shrunken distorted leaves and flower stalks, and produce few, if any, marketable fruit. Miticides such as Kelthane® and Portal® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside. Thionex® may also be used, but registration of this product on strawberries will run out in July of this year.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mites can be a problem in the spring, especially for plants under row covers. This is often where we first find mites. Spider mites will reproduce rapidly when warmer weather arrives, so it is important to scout for them regularly. Spider mites feed on the undersides of strawberry leaves, rasping the plant tissue and sucking the sap. Infested leaves will develop yellow flecking and a bronzed appearance. The plants become weakened and stunted. Fields that have had excessive nitrogen fertilizer and/or row covers tend to be most susceptible to mite injury. To scout for mites, collect 60 leaves from various locations in the field and examine the undersides for the presence of mites. Mites are very small – you may need a hand lens to see them. Chemical control options for two-spotted spider mites include Acramite®, Portal®, Nealta® Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol® and JMS Stylet Oil® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

Root weevil management
Fields that were infested with root weevils last summer should be inspected for grubs this spring. Infested plants appear week and stunted, usually in somewhat circular patches in a field. Digging under the plants will reveal small (1/4”-1/2”) crescent-shaped legless grubs. Typically, the grubs begin to pupate when the plants are in bloom. A soil drench of Platinum® (thiamethoxam) insecticide during the spring and/or fall when the grubs are active in the soil can provide control. However, Platinum® has a 50 day pre-harvest interval, so it is too late for applications in most fruiting fields this year. Platinum® may also be used as a pre-plant or planting treatment for root weevils. It is not too late to put on an application of nematodes to control the grubs (optimal timing is about mid-May). Two species of nematodes appear to offer the best control of root weevil grubs. Heterorhabditis bacteriophora (Hb) appears to be the best candidate for control of root weevils when the soil temperature is above 60 degrees, and is available from Green Methods, www.greenmethods.com/site-info; the Integrated Biocontrol Network, www.biconet.com; and Koppert Biological Systems, www.koppertonline.com.

Nematodes are living organisms and they can be killed if they are misapplied. Order nematodes ahead of time and be ready to apply them through a sprayer or irrigation soon after they arrive. Refrigerate them if you cannot apply right away. Do not apply nematodes using a sprayer with a piston pump. Use clean equipment, removing all screens finer than 50-mesh. Apply nematodes in early morning or evening in a high volume of water to already moist soil, pre-irrigating if needed. Apply another ¼ inch of irrigation after application to wash them onto and into the soil. Researchers and suppliers recommended 250 (if banded in the row) to 500 million per acre, at a cost of $100-$200 per acre depending on volume and source. Nematodes tend to work best in heavily infested fields. Strawberry plants can recover their vigor remarkably well if crown feeding has not occurred and diseases haven’t taken over the roots.

Once the adults become active in July, bifenthrin (Brigade®) will provide some control if used at the highest labeled rates. The best timing for this spray is at night during the peak feeding activity of adults, before they start laying eggs, or about the time harvest ends.

White Grub

White Grub, Photo by David Handley

White grubs: Weak growth noted in fields this spring may also be the result of white grubs feeding on the roots of newer plantings. These grubs are the larvae of beetles, including European chafer and Asiatic garden beetle. They differ from the larvae of black vine weevil and strawberry root weevil in that they have legs and a swollen anterior (rear end), and they tend to be larger. Their feeding weakens the plants by reducing the number of roots. The grubs can be found by pulling up weak plants and sifting through the soil that surrounded the roots. Controlling white grubs once they have become established in a field can be difficult. These tend to be more of a problem in new fields that have been planted following a grass rotation crop, because the adults prefer to lay their eggs in sod. Admire Pro® and Platinum® insecticides are labeled for control of white grubs and should be applied within two hours of irrigation or rainfall to be sure the chemical gets into the root zone. Admire Pro® requires a 14 day to harvest interval, while Platinum® requires a 50 day pre-harvest interval.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Diseases: Bloom is a critical time to protect strawberry fruit against gray mold caused by the fungus Botrytis cinerea, especially when conditions have been damp. Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease. If you tank mix insecticides and fungicides, avoid spraying when bees are active. Botrytis cinerea overwinters on old leaves and plant debris. Fruit infections take place almost exclusively through the flowers, so gray mold control efforts must be focused on the bloom period. If the bloom period is dry and/or good fungicide coverage is maintained, incidence of gray mold at harvest should be low.

There are several excellent fungicide choices for control of gray mold in strawberries. Elevate® (fenhexamid) has good to excellent activity against Botrytis. Captevate® is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate® alone. Switch® (cyprodinil and fludioxonil), Scala® (pyramethanil) and Pristine® (pyraclostrobin and boscalid) are also excellent products for gray mold control. Topsin M® + captan is also a good fungicide combination, but remember that captan is strictly a protectant and can be washed off by rain or irrigation water. Thiram is similarly effective but also susceptible to wash-off.

The fungicides Cabrio® (pyraclostrobin) and Abound® (azoxystrobin) are NOT suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases. All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M® (1 day) and thiram (3 days). Remember to alternate fungicides with different modes of action for resistance management purposes.

Red Stele Symptoms on Strawberry Plant

Red Stele Symptoms on Strawberry Plant, photo by David Handley

Red stele root rot
Although early spring conditions have not been especially conducive to red stele development, you should still be alert for this root rot if any fields appear to be weak, stunted or dying. To diagnose red stele, pull up a few plants that look weak and scrape the roots of these plants to see if the center of the root, known as the stele, is rusty red in color, instead of the normal white. The red color would indicate an infection. Red stele is caused by Phytophthora fragariae, a soil pathogen that infects roots when soils are wet with temperatures around 50°F. The pathogen grows into the roots causing the plants to become weak, stunted and to eventually die. Symptoms are most evident in the spring, and can be mistaken for winter injury. Ridomil Gold®, Alliette® or Phostrol® are fungicides that can be applied in the late fall or early spring for control of red stele. Many varieties have some level of resistance to the disease, but the most effective management strategy is to plant only into well-drained soils, and/or plant onto raised beds.

Powdery Mildew

Powdery Mildew, photo by David Handley

Powdery mildew: This fungus disease may first show up as purple or red blotches on the leaf petioles and flower stems in strawberry fields. Most of us are more familiar with the later symptoms of upward curling of the leaves and white, powdery growth on the undersides of the leaves. Check your fields for pinkish purple leaf and flower stem lesions as new leaves emerge. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet Oil® are presently registered to control powdery mildew.

Angular leaf spot is a bacterial disease that is characterized by translucent leaf spots that may turn yellow and eventually black. The symptoms tend to start on the lower leaves but may move upwards as bacterial spores are splashed up by rain or irrigation water. Infection of the calyxes may result in a blackening of the berry stems and caps, reducing their marketability. Bacterial angular leaf spot is favored by extended cool, wet weather and nights with temperatures close to freezing. Frequent irrigation for frost protection can greatly encourage the development and spread of the disease, as will extended cool, damp weather. Susceptibility to this disease appears to vary significantly between varieties.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

The copper-containing material Kocide®, can reduce the spread of this disease. Start spray applications before bloom to prevent multiplication of the bacteria on the leaves before they jump to the berry caps. Application of copper sprays after bloom can result in fruit injury and is not recommended. Hydrogen dioxide (OxiDate®) may also have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

Other Berries:

Raspberries are showing significant winter injury in some fields, especially among the less hardy varieties. Often more winter injury becomes apparent once the floricanes start to flower. Tip dieback often occurs due to winter damage to the vascular tissue within the canes.

Highbush blueberries are also showing significant winter injury in some fields, especially in more southern regions. Dark brown or black discoloration of last year’s shoot growth, and/or shriveling of the shoot tissue indicate winter injury and desiccation, frequently resulting in death of the flower buds. Mummy berry spores will soon start to be active. Expect infection periods to occur over the next few weeks, anytime there is a significant moisture event (rain, mist, fog). Protectant fungicides for mummy berry include Indar®, Orbit®, and Quilt Excel®.

The Twilight Meeting will be held on June 9th at MacDougal Orchards in Springvale. This meeting will focus on irrigation and will feature Trevor Hardy from Brookdale Farms to discuss irrigation options for fruit and vegetable growers. George Hamilton of the University of New Hampshire will also be on hand to discuss calibration of sprayers. We’ll have a tour of some of the fruit plantings on the farm and see the new deer exclusion project being set up around the orchard. We’ll also discuss the pest situation around the state, and the current crop outlook. The meeting will run from 4:00 p.m. to 7:00 p.m. More details will follow. Hope to see you in Springvale.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Ave
Monmouth, ME 04259         Orono, ME 04473
207.933.2100                          1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 7 – July 10, 2015

Monday, July 13th, 2015

StrawberriesStrawberry IPM Newsletter No 7 – July 10, 2015

RENOVATION AND WEED MANAGEMENT ISSUE

Time to Get Your Strawberry Beds Ready for Next Year

Be Ready to Manage Pests in Day-Neutral Strawberries

A very cold, long winter resulted in some moderate winter damage to strawberries in some fields, but more than adequate snow cover prevented more serious injury. Good spring growing conditions with little to no frost issues resulted in a pretty good crop in most fields. Fruit size was a bit off in some fields, likely due to very dry conditions in April/May. Weather conditions for harvest were also pretty good and customers were out in force early, although some growers with late fruit had difficulty in keeping the pickers coming after early July. Pest pressure in most fields was light throughout the season. Insects, including tarnished plant bug and strawberry bud weevil or clipper appeared fairly late and often in low numbers. Spider mites were hardly an issue, and cyclamen mites were also low this spring. Root weevils and white grubs were an issue in some fields, especially where problems had been observed last year. Applications of soil insecticides and/or parasitic nematodes seem to have reduced the problem in most situations. Disease pressure was also light in most fields. Dry weather and timely fungicide sprays kept gray mold to a minimum, and foliar diseases, such as powdery mildew and leaf spot only began to show up towards the end of the season.

Don’t forget about your strawberries after harvest. Follow the recommended renovation steps listed below for matted row strawberries as soon after harvest as possible; and continue to scout for and manage disease, insect and weed problems as they arise. Some of the more common issues to be alert for during the summer are listed below.

DISEASES
Foliar diseases should be monitored in your fields by regularly examining leaves. All of the common leaf diseases were present in fields this spring and we should expect that they would continue to be a problem through the summer. The most common summer diseases are powdery mildew, leaf spot and leaf scorch. Fungicides available for these diseases include captan, Topsin-M®, Cabrio®, and Pristine®. See the New England Small Fruit Management Guide for detailed descriptions of these diseases and their management.

Powdery Mildew

Powdery Mildew, photo by David Handley

Leaf Scorch

Leaf Scorch, photo by David Handley

Black root rot is a disease complex which can be brought on by a combination of problems, including nematodes, soil fungi (Rhizoctonia, Pythium), herbicide carryover, and soil compaction. Plants become weak and may wilt and die. Roots on affected plants are black and poorly developed. This tends to be a problem in fields that have been in strawberries constantly for many seasons, and in fields that are under stress in other ways, such as winter injury. Rotating fields to crops other than strawberries for at least three years is an important management strategy for black root rot. Improving soil drainage and breaking up hardpans in the soil may also help. Pre-plant root dips with azoxystrobin (Abound®) may also reduce incidence of black root rot in some fields.

INSECTS
If black vine weevils or strawberry root weevils are a problem in a strawberry field that you would like to carry over, bifenthrin (Brigade®, Bifenture®) can be applied when adult feeding is noticed (usually until mid-late July). Look for notching along the leaf edges and the presence of the black or brown snout beetles. Applications should be made at night when these insects are active, and the highest rate of the insecticide should be used. For control of the grubs a soil drench of Platinum® (thiamethoxam) insecticide should be applied during the fall and/or early spring when the grubs are active in the soil. This product has a 50 day pre-harvest interval and may also be used as a pre-plant or planting treatment for root weevils. Parasitic nematodes such as Heterorhabditis bacteriophora or Steinernema feltiae can also be applied to provide control of root weevil grubs in late August. Nematodes require specialized handling and application. Contact us or talk with one of the suppliers for more details. See the New England Small Fruit Management Guide for sources.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

White grubs have been a problem in many fields in recent years. The grubs may be the larvae of several species of scarab beetles, including June beetles, rose chafers, Japanese beetles, Asiatic garden beetles and European chafers. The beetles lay their eggs in June and July and the grubs feed on the roots of strawberries from July through mid-September. Affected plants will be stunted and wilted and may die during dry periods. Pulling up plants reveals that roots have been chewed off about an inch below the soil line. Sifting through the soil below the plants may reveal the whitish crescent-shaped grubs which can range in size from 3/8 inch to almost 1 ½ inches long, with six legs near the head and a swollen rear-end. The two most effective periods to treat plantings for grubs are in the spring prior to when they pupate (May) and in the late summer when the next generation is actively feeding (late August). Materials should be applied with plenty of water to moist soil to be sure they reach the root zone. Materials currently registered for control of grubs include Platinum® and Admire Pro®. Parasitic nematodes can also provide control of grubs and should be applied with similar timing. Nematodes are very sensitive to ultraviolet light and dehydration and must be applied with lots of water. See the New England Small Fruit Management Guide for sources of parasitic nematodes.

Strawberry rootworm (not root weevil) is a small (1/8″) dark brown to black beetle which feeds on strawberry foliage, causing it to look skeletonized. The small larvae feed on strawberry roots, further weakening the plant. Adult feeding damage on the leaves usually occurs in late July through August. Heavy rootworm feeding weakens strawberry plants so control is warranted when injury is noticed.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by James Dill

Potato Leafhopper

Potato Leafhopper, photo by James Dill

Keep a lookout for potato leafhoppers, which can weaken strawberry plants and spread disease. The potato leafhopper does not overwinter in Maine, but must fly in from southern states. These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked. Symptoms are often first noticed in new strawberry plantings, but leafhoppers will also infest older plantings and a variety of vegetables, flowers and fruit crops. To scout for leafhoppers, brush the leaves of the plants with your hand. The small, whitish adults can be seen flying off the plant. Examine the underside of some injured leaves. Look for small, light green leafhopper nymphs. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Controls for potato leafhoppers include malathion, carbaryl or Provado®.

MITES
Two-spotted spider mites can increase significantly during the summer. Continue to take leaf samples for spider mites throughout the summer. If more than 25% of a 60-leaf sample has mites, controls should be applied. Summer is an ideal time to use predatory mites to control pest mites, because they prefer warm temperatures, and there is less chance of an insecticide spray that might kill them. Amblyseius fallacis can provide good control of two-spotted spider mites when they are released at a rate of about 10,000 mites per acre. Predator mite releases should only be made after a spider mite infestation has been found in the field. Releasing predators into a clean field will often result in them dying, due to a lack of food. See the New England Small Fruit Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Cyclamen Mite Damage on Strawberry Plant

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

Cyclamen mites: If your field had cyclamen mite symptoms this spring, summer is a good time to control them. Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite. These mites are very small and reside down in the crown of the strawberry plant feeding on the developing leaves. They are very hard to see, even with magnification. Miticides such as Thionex®, Kelthane® or Portal® can be effective, but must be applied with lots of water to be sure that the material is carried down into the crowns.

WEEDS
Weeds can become a big problem during the summer because they are often forgotten among all the other demands on our time and because of limited control options. However, the importance of good weed management should not be underestimated. Keeping weeds under control this summer will prevent future infestations. Here’s a summary of weed control options for strawberries:

  1. Cultivation: Following renovation, cultivation between strawberry rows can provide effective temporary control of annual weeds. Several types of cultivators are available which will work well in strawberry beds. Cultivators can also be used to help sweep runners into the plant rows.
  1. DCPA (Dacthal®): A pre-emergent herbicide used in the early spring, late fall or after renovation. It offers good short-term control of some annual broadleaf weeds and grasses. It is weak on ragweed, galinsoga, smartweed, shepherd’s purse and mustard. Its action will be improved if worked into the soil by irrigation or light cultivation, and it tends to work best in lighter, warmer soils. This may be used as an alternative to terbacil or napropamide when there is a high risk of plant injury from those products.
  1. Napropamide (Devrinol®): A pre-emergent herbicide which provides good control of annual grasses, volunteer grains and some broadleaf weeds. It is typically applied just before mulching in the fall. Split applications have become popular due to the loss of other pre-emergent herbicides, e.g. half maximum rate application after renovation or in late summer after desired daughter plants have rooted, and a second half rate application once the strawberry plants are dormant. Napropamide should be activated by irrigation, rainfall or light cultivation within 24 hours of application. Repeated long-term use of this material, i.e. with no crop rotation, may eventually result in poor daughter plant establishment, due to rooting inhibition.
  1. Terbacil (Sinbar®): An effective pre-emergent herbicide with some post-emergent activity, which should be applied at renovation time – after mowing and tilling the beds, but before new growth begins. A second application can be made in late fall, after the plants are dormant. No more than 6 oz. may be applied in a single application, and no more than 8 oz. may be applied in one season. An example of one season’s use could be 5 oz. applied at renovation and 3 oz. applied in the late fall, the latter in addition to napropamide or DCPA. Terbacil can cause injury to strawberry plants. It is important to determine appropriate rates for each location.
  1. Clopyralid (Spur®): One application per crop per year following harvest to emerged weeds. Apply uniformly in a minimum of 10 gallons of water per acre. Do not tank mix with other herbicides. Offers control of clover, dandelion and thistle.
  1. Sethoxydim (Poast®): A post-emergent herbicide for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Do not use sethoxydim within 6 weeks of terbacil (Sinbar®) applications, to avoid leaf injury. Sethoxydim should be used in combination with a crop oil concentrate. Do not tank mix with 2, 4-D.
  1. Clethodim (Arrow®, Prism®, Select®): A post-emergent herbicide, similar in activity to Poast®, for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Clethodim should be used in combination with a crop oil concentrate.
  1. Paraquat (Gramoxone Inteon®): A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Paraquat will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. It should be used in combination with a nonionic surfactant. Paraquat should not be applied within 21 days of harvest or more than three times in one season.
  1. Pelargonic Acid (Scythe®): A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Scythe® will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. This product has a relatively low toxicity and no residual soil activity. It has a strong, unpleasant odor.
  1. 2,4-D Amine (Formula 40®, Amine 4): A post-emergent herbicide effective on most broadleaf perennial weeds. It will not control grasses, nor offer any pre-emergent control. 2,4-D should be applied immediately after harvest is complete if emerged broadleaf weeds are a problem. After application, the bed should be left undisturbed for three to five days, before mowing the leaves off the plants. This allows time for the material to be taken in by the weeds. This material can also be used when the plants are dormant (late fall or early spring) to control winter annuals and biennials. Fall applications may result in injury to the strawberries if the plants are not completely dormant. Do not tank mix 2,4-D with sethoxydim (Poast®).
  1. Flumloxazin (Chateau®): A pre-emergent herbicide for control of broadleaf weeds, including dandelion and shepherd’s purse. For use in the fall when plants are dormant for control of weeds the following spring.
  1. Pendimethalin (Prowl H20®): A pre-emergent herbicide that may be applied as a band with a shielded sprayer between the rows of strawberries. No weed control will be provided within the plant rows, and contact of this product on the strawberry plants will cause injury. May not be applied within 35 days of harvest.

The use of herbicides alone rarely gives complete weed control. Some hand weeding will be necessary. To provide good weed control throughout the life of a strawberry bed, growers should concentrate on crop rotation and good pre-plant weed control.

Strawberry Bed Renovation Review

Bed renovation should begin as soon after harvest as possible. The earlier the beds get renovated, the more time runner plants have to develop, which means larger crowns and more flower buds for next year. Early renovation also improves weed management by tilling in many weeds before they go to seed, and can help with insect and foliar disease control by interfering with life cycles at a critical stage of development. The first step in the bed renovation process is to determine which beds should be carried over for another year and which should be plowed down and put into a crop rotation. Beds that did not suffer much from winter injury, had good production and a good plant stand with no major weed, insect or disease problems should be carried over for another year. Beds that do not meet these criteria should be plowed down and seeded to a suitable cover crop to reduce weed, insect and disease problems that have developed, and to increase soil organic matter content. Ideally, beds that are plowed down should be rotated out of strawberries for at least three years. If properly managed, crop rotation will greatly reduce pest problems and improve the vigor and longevity of strawberry beds without the need for soil fumigation.

Strawberry Bed Renovation

Strawberry Bed Renovation, photo by David Handley

Renovating a strawberry bed is basically a thinning process to promote healthy new growth that can support a good crop next spring. While some parts of the following renovation scheme may be modified for individual situations, all beds should undergo the following steps once harvest is complete.

  1. Broadleaf weed control: If perennial broadleaf weeds such as dandelion, shepherd’s purse, daisy or goldenrod are a problem and/or a high population of annual broadleaf weeds such as lambsquarters, sorrel or pigweed are present, hand-pull as many as possible, especially within the plant rows, and/or apply 2,4-D amine (Formula 40®), or clopyralid (Spur®).
  1. Leaf mowing: Four to five days following the 2,4-D application (or immediately if 2,4-D was not applied) mow off the leaves of the strawberries about 1 ½ inches above the crowns. If the planting is weak, it is recommended that this step of the renovation process be skipped.
  1. Fertilization: Apply 40 to 60 pounds of actual nitrogen per acre (use the higher rate on sandy soils and fields where growth has been weak). Phosphorus and potassium applications should be made according to soil test recommendations. Soil testing kits and information are available from your county Cooperative Extension office.
  1. Plant thinning: For the single matted row system, strawberry plant rows should not be any wider than 24 inches. After mowing off the leaves, till the sides of the rows to narrow the beds back to a width of 12 to 18 inches. Use the wider setting for varieties that tend to throw few runners or any fields experiencing drought stress. Set the tiller so that it incorporates the mowed leaves and spreads about one inch of soil over the remaining crowns at the same time. This will reduce leaf disease and mite problems, and help stimulate new root growth on the remaining plants.
  1. Pre-emergent weed control: To control annual weeds, apply terbacil (Sinbar® 80WP) according to label directions (2 to 6 oz. per acre). Be sure to follow all label precautions. To avoid plant injury, do not use terbacil if you do not intend to mow off the leaves. Napropamide (Devrinol®) or DCPA (Dacthal®) may be used as an alternative to terbacil at this time, as described below. If you are not using herbicides, regular cultivation, before weeds are more than 2” tall, will be needed throughout the summer.
Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

  1. Subsoiling: Soil compaction caused by tractor and picker traffic in the field can cause soil drainage problems and interfere with good root development. Using a subsoiling blade between the rows will break up compacted layers of soil and improve water infiltration. Subsoiling is best done late in the renovation sequence to prevent interference from straw and crop residues.
  1. Irrigation: To encourage rapid plant growth and get the most out of fertilizers and herbicides, irrigate the beds regularly. Strawberries will grow best if they receive 1 ½ inches of water per week during the growing season.

Don’t forget your plants once these renovation steps are completed. Check the strawberry fields regularly during the summer for pest problems. Finding and managing problems early can prevent major problems next spring. Pay close attention to the following items.

NUTRITION
Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen should be applied in mid- to late-August to stimulate flower bud development. One way to determine the nutrient status of strawberry plants during the summer is to have a leaf tissue analysis done. Tissue analysis offers a view of what is happening within the plant, and can spot any nutrient deficiencies. In combination with regular soil tests, tissue analysis will provide a complete picture of a field’s fertilizer needs. For more information about tissue analysis contact: Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 207.581.2945.

Pest Management for Day-Neutral Strawberries

Most of the important pests that damage June-bearing varieties can be as much or more of a problem on day-neutral types. Because day-neutral strawberries will have buds, flowers and fruit all occurring at the same time, it is critical to pay close attention to the required number of days to harvest after a pesticide application, to be sure you can safely harvest ripe fruit while still protecting buds and blossoms. Some of the more important pests are listed below, along with currently recommended pesticides and days to harvest as stated on current labels.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted wing drosophila (Drosophila suzukii) is a new pest, which is likely to be a concern for day- neutral strawberries, fall raspberries and blueberries. This is a small fruit fly, similar to those that hover around the bananas in your kitchen. However, this species will lay its eggs on fruit before it ripens, resulting in fruit that is contaminated with small white maggots just as it is ready to pick. Infested fruit quickly rots and has no shelf life. This insect can complete a generation in under two weeks, with each adult female laying hundreds of eggs. Therefore, millions of flies can be present soon after the introduction of just a few into a field. Frequently repeated insecticide sprays (1 to 2 per week) may be needed to prevent infestations once the insect is present in a field. Spotted winged drosophila can successfully overwinter here, although it may not build up to damaging levels until late in the summer. We have set out monitoring traps for spotted winged drosophila in fruit plantings around the state to determine the activity of this pest in Maine. However, these traps may not provide adequate early warning, i.e. when we find them in a trap they are probably already established in the field. Products that provide good control of drosophila on strawberries include Radiant®, Brigade®, Danitol®, malathion and Assail®. Keeping fields clean of over-ripe and rotten fruit will also help reduce the incidence of this insect. For more information on identifying spotted wing drosophila and updates on populations around the state, visit our SWD blog. Other spotted wing drosophila resources include Michigan State University’s website, Penn State’s website, and University of New Hampshire’s website.

Tarnished plant bug: This is one of the most prevalent and persistent pests of day-neutral strawberries, because summer flowering coincides with peak populations of this insect. Adult and nymph stages feed on the flowers and developing fruit, causing them to have seedy ends and other malformations. Regular insecticide applications are often required to keep the damage in check. Scout the flower clusters for adults and nymphs often to determine if controls are necessary. Insecticide products for tarnished plant bug are included in the following table.

Tarnished Plant Bug on Strawberry

Tarnished Plant Bug on Strawberry Flower, photo by David Handley

Tarnished Plant Bug
Product Days to Harvest
Brigade® 0
Pyganic® 0
Assail® 1
Dibrom® 1
Rimon® 1
malathion 3

 

Two-spotted spider mites: Mites can become a problem during the summer when the growing conditions are warm and dry. In addition to infesting the leaves, mites can move onto the fruit, reducing marketability. Plants that are drought-stressed, over fertilized with nitrogen, or prone to dust covering, e.g. growing beside a dirt road, are especially prone to mite infestation. Predatory mites can be an effective means to control spider mites and keep them in check over the season. Releases should only be made when spider mites are present in the field to provide the predators with a source of food. Most of the products labeled for controlling spider mites will also kill predatory mites; so do not use these products after predators have been released. Scout for mites often during the season by examining the undersides of the leaves. Control is warranted if more the 25% of leaves examined have mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-Spotted Spider Mites
Product Days to Harvest
Brigade® 0
Zeal® 1
Vendex® 1
Acramite® 1
Danitol® 2
Agri-Mek® 2
Oberon® 3
Savey® 3
Kelthane® 3

Potato leafhoppers, sap beetles, thrips and spittlebugs may also become problems on day-neutral strawberries, but are less frequently observed than tarnished plant bug and spider mites. Recommendations for these insects can be found in the current edition of the New England Small Fruit Management Guide.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Foliar and fruit diseases also need to be managed on day-neutral strawberries, and should be controlled in much the same way as they are for June-bearing varieties. Most of the fungicide products labeled to control gray mold, powdery mildew, leaf spot and leaf scorch have either zero or one day to harvest, so protecting blossoms at the same time as fruit is near harvest should not be a problem; but be sure to check labels carefully and schedule your sprays and harvests accordingly. Anthracnose fruit rot can be especially troublesome for day-neutral strawberries, because it grows well under warm conditions and spreads by splashing water, which is encouraged on plastic mulch. Fungicides registered for control of anthracnose include Cabrio®, Abound®, Pristine® and Switch®, all of which have zero days to harvest restriction.

Visit the 2014-2015 New England Small Fruit Management Guide online for more detailed pest information.

Hold the Dates:
Fruit & Vegetable Growers Field Day at Highmoor Farm: Wednesday July 22, 9:00 a.m. to 3:00 p.m. Call 207.933.2100 or visit the Highmoor Farm Field Day website for registration information. Please register early!

New England Vegetable & Fruit Conference will be held on December 15-17 in Manchester, NH. Details and registration information are coming soon. Please visit the NEVFC website.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Where brand names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against products with similar ingredients. Always consult product label for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Published and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914, by the University of Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System


 

Strawberry IPM Newsletter No. 6 – June 18, 2015

Friday, June 19th, 2015

StrawberriesStrawberry IPM Newsletter No. 6 – June 18, 2015
Click on photos to enlarge.

STRAWBERRY HARVEST GETS UNDERWAY!

Crop Prediction: Good to Moderate

Situation: Harvest is underway in Southern Maine and more northern areas are soon to follow. We’ve been getting calls on bird damage, but otherwise the pest pressure has been very low in most fields this week. Fruit size, especially on secondary and later fruit appears to be smaller this year, which may be a result of our very dry spring and/or cold winter. Regardless, the overall quality looks good and yields look to also be good, especially in areas that received adequate rain or irrigation during the fruit development period. Our annual strawberry bed renovation issue will be posted in two to three weeks. In the meantime, we hope the information provided by the Strawberry IPM Newsletter has helped you make the best pest management decisions possible for your fields. Happy harvest!

Tarnished plant bug nymphs were only found in one field this week, and populations were below the management threshold. Overall, tarnished plant bug pressure has been very light this spring, and hopefully growers were able to reduce sprays as a result. However, if you are also growing day-neutral strawberries for a late summer and fall crop, begin scouting for tarnished plant bug as soon as the plants begin to flower. Tarnished plant bug populations are at their highest in the late summer, so damage on these fruit can be severe. Often control must occur when both flowers and nearly ripe fruit are present, so select insecticides with short residuals and days to harvest. Some examples include Assail®, Brigade®, Bifenture®, and Dibrom®.

Tarnished Plant Bug on Strawberry

Tarnished Plant Bug on Strawberry Flower, photo by David Handley

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mite activity has been low in most fields throughout the season, despite dry conditions, which can promote their development. Mite populations can build up almost anytime, especially in hot, dry, dusty conditions; so growers should continue to scout for mites throughout the summer and be prepared to manage them if they build up after renovation. Spider mites can become a problem on day neutral strawberries in the late summer and fall, so scout these plantings regularly for mites.

Leaf diseases, including powdery mildew, leaf spot and leaf scorch, are at very low levels as we come into harvest. These diseases can pop up anytime during the season, so continue to be on the lookout throughout harvest and following renovation.

Leather rot (Phytopthora cactorum) and Anthracnose fruit rot (Colletotrichum acutatum) can be a problem on day-neutral strawberries ripening during the late summer and fall, especially following heavy rain showers and humid weather. Water splashing on the surface of plastic mulch can lead to the development and rapid spread of these diseases. Fungicides effective for gray mold may not provide control of leather rot and may not be very effective for anthracnose. Aliette®, Agri-Phos® or Phostrol® are recommended for leather rot, while Cabrio® and Pristine® are effective for anthracnose.

Review: Keeping Strawberries Fresh for Market
Strawberries are highly perishable and can fall into decay very rapidly if not handled properly. Train your pickers and sales people regarding how to keep the fruit in the best condition possible all the way from the field to the customers, in order to maintain the best quality and prolong shelf life. Pickers should be careful not to bruise fruit during harvest, and not to put damaged fruit into the containers. All harvested fruit should be cooled immediately to slow respiration. This will greatly extend shelf life and reduce the incidence of post-harvest fruit rots. Strawberries cool most efficiently if harvested early in the morning before they build up any field heat. Place fruit into refrigerated storage quickly and keep it out of direct sunlight. Fruit should be stored at 32° Fahrenheit and 95% relative humidity. Cold air should be moved through the boxes or flats of fruit with a circulating fan and/or exhaust fan to cool most efficiently. Placing a sheet of plastic over the trays in the cooler can reduce moisture build up on the berries. Temperatures lower than 32°Fahrenheit may freeze the fruit and ruin its fresh quality. A small, well-insulated building cooled with air conditioners and fans can provide effective temporary storage for strawberries. If you don’t have refrigeration facilities, keep the fruit as cool as possible by harvesting when air temperatures are cool, and keeping it out of direct sunlight. Transport the fruit to market as quickly as possible, and harvest only what you think you can sell in a day.

Girl with Quarts of Strawberries

Strawberry Harvest, photo by David Handley

Annual Pre-Harvest Checklist for Pick-Your-Own
It’s that time again! As harvest approaches, its time to make sure that your farm is ready to give your customers the best possible picking experience. Take our annual review below to evaluate your customer readiness.

√ A phone message with picking conditions and opening and closing times is regularly updated.

√ Signs to the farm are neat and easy to read.

√ There is easy access to the fields and plenty of parking.

√ Someone is ready to greet customers and offer parking instructions and directions to the field.

√ Access to the field is free of hazards.

√ Transportation is provided for the elderly and disabled.

√ The rules regarding picking are clearly posted.

√ Someone is in the field to show customers where to pick and to answer questions.

√ There are plenty of picking containers available.

√ Clean restroom and hand washing facilities are available.

√ Someone is available to help customers carry fruit out of the field.

√ The checkouts are fast and efficient.

√ Beverages are available.

√ Shade and seats are available for customers wanting to rest.

√ The help are friendly and knowledgeable.

A friendly, clean, and organized atmosphere will leave a lasting impression on your customers, encouraging them to come back and to recommend your farm to their friends.

Other Crops: Some blueberry fields are showing significant winter injury, including dead, dark brown or black shoots, usually at or near the top of the bushes. Pruning out such injury once the plants have started to grow does not appear to help the plants much. However, Phomopsis twig blight often infects blueberry branches through the cold-injured tissue. This fungus disease causes new shoots to suddenly wilt and turn black. Individual branches or canes on the bushes may also turn brown. This is referred to as “flagging”. Infected branches may be pruned out. Sterilize pruners before moving on to another bush to prevent further spreading the fungus. Lime sulfur sprays used prior to leafing out in the spring and some copper materials can help control Phomopsis. See the New England Small Fruit Management Guide for more details.

entrance to Highmoor Farm

Highmoor Farm, photo by Pam St. Peter

Hold the Date! Details Soon!
Highmoor Farm Field Day
Wednesday, July 22, 2015
52 US Route 202, Monmouth, Maine 04259

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 5 – June 12, 2015

Friday, June 12th, 2015

StrawberriesStrawberry IPM Newsletter No. 5 – June 12, 2015
Click on photos to enlarge.

STRAWBERRY HARVEST GETTING STARTED IN SOUTHERN MAINE

Insect and Disease Activity Remains Low

Situation: Southern and mid-state fields remain pretty dry, while fields in the more northern and western part of the state have been getting some heavy showers this week. A few ripe berries are being picked in far southern Maine and some of those fields may open for pick-your own early next week. More northern growers are still about a week away. The pest situation remains fairly calm, although the spider mites may soon become more numerous, as should be expected with warm, dry weather.

Strawberry bud weevil or “clipper” activity is showing up on late blooming varieties, but most fields are beyond the full bloom stage. Thus, clipper no longer presents a serious threat. Remember that clippers will move onto raspberry and blackberry plants to lay eggs and clip buds once the strawberries have gone into bloom.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug activity continues to be very low this week. No fields were found over threshold of 4 or more flower clusters infested per 30 sampled. Tarnished plant bug remains a threat throughout the bloom and petal fall stage, and should be scouted for regularly on the flower clusters and developing fruit. Insecticide options include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Two-spotted spider mite activity remains low in most fields, although one planting in Minot was over threshold with 25% of leaves sampled having mites. Mite populations should be expected to increase if warm dry conditions continue, so keep scouting for them.

Sap beetle on strawberry

Picnic Beetle (left) on Strawberry, photo by James Dill

Sap beetles and picnic beetles are sometimes a problem as we start harvesting berries. The 1/8-inch long, dark brown beetles chew small holes in ripening fruit, similar to slug injury. They may be seen in the holes they’ve chewed into ripe fruit, but often drop to the ground when disturbed. The best management strategy for sap beetles is good sanitation. Keep the field free of overripe fruit by picking often and thoroughly. Insecticide sprays for this pest can be effective, but should be a last resort during the harvest period. Brigade®, Assail®, Dibrom®, and PyGanic® are registered for control of sap beetles with pre-harvest intervals ranging from 12 to 24 hours. Read the product label carefully for this and other application instructions and restrictions.

Entrust® Insecticide May Lose Berry Registration
Dr. Richard Cowles of the Connecticut Agricultural Experiment Station recently shared a letter he received from Dow AgroSciences stating that the registration of Entrust® insecticide (active ingredient spinosad) may be withdrawn by the company due to reports of misuse (primarily overuse) by growers, which could threaten the viability of the product by encouraging the development of insect resistance to it. Entrust® has been a very important tool for the management of spotted wing drosophila (SWD), especially for organic berry growers, as the product is Organic Materials Review Institute (OMRI) approved. Dr. Cowles states “This is not an idle threat to withdraw sales of Entrust® to New England states.  Abuse of Conserve SC® by greenhouse growers in the Southeast led to widespread flower thrips resistance, whereupon Dow withdrew marketing of that product to that region.  The problem that I see is that there currently are very few effective proven alternative options to spinosad available to organic growers, besides frequent clean harvesting of crops and use of exclusion netting (for certain crops).”

All berry growers should intensively monitor for SWD adult activity with effective traps and baits, and only consider insecticide sprays when both (a) SWD adults are present and (b) fruit are ripening sufficiently to almost be susceptible to egg laying.  The prospect of losing an important tool in the management of SWD emphasizes the importance of following the label directions of pesticides in all regards, including the limitations for use of Entrust® on individual crops and on entire farms, due to concerns for insecticide resistance prevention.

Diseases: For those fields that have received significant rain or overhead irrigation recently, remember that any moisture will stimulate the release of botrytis spores. Late varieties that are still in the bloom stage should be protected with a fungicide spray.

Leaf diseases, including powdery mildew, leaf spot and leaf scorch, have remained at very low levels this week. Fungicide sprays for gray mold often also provide control of foliar diseases. However, it is important to keep an eye out for symptoms in the field, especially following rain, because infections are likely to occur under warm, wet conditions.

Powdery Mildew

Powdery Mildew, photo by David Handley

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Leather rot (Phytopthora cactorum) and Anthracnose fruit rot (Colletotrichum acutatum) have been reported this week on ripening day-neutral strawberries grown on black plastic mulch. Warm weather combined with water puddling on the surface of the mulch can lead to the development and rapid spread of these diseases. Fungicides applied for gray mold are generally not effective for leather rot and may not be very effective for anthracnose. Foliar sprays of Aliette®, Agri-Phos® or Phostrol® are recommended for leather rot, while Cabrio® and Pristine® are most effective for anthracnose.

Birds, specifically cedar waxwings will be moving into fields to start feeding on ripe fruit, if they haven’t already. These birds can destroy many of the early ripening fruit, despite our best efforts to scare them off. Only by keeping a near constant presence in the field and eliminating roosting sites can you reduce the damage. Usually, they are discouraged once the fields start to be regularly harvested and customers are present. Songbirds are protected by law and should not be killed. However, permits may be issued for killing birds by the U.S. Fish and Wildlife Service if they receive a recommendation for such a permit from the Maine Wildlife Services Office (part of the USDA Animal and Plant Health Inspection Service) in Augusta, along with an application from the grower. There is a $50 fee for the application, and it may take over a month for the permit to be processed. However, the permit is good for one year, so if you have problems this season, you may consider applying for a permit this winter, which would allow you an option to kill birds, if necessary, next season. The Wildlife Damage Office has recommendations for managing birds in crops, and also has some control options available through their office. For more information on permits or bird control contact the office in Augusta at 207.629.5181. The office is located in the Capital West Business Center at 79 Leighton Road in Augusta.

Hold the Date!
Highmoor Farm Field Day is on Wednesday, July 22, 2015.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 4 – June 5, 2015

Friday, June 5th, 2015

StrawberriesStrawberry IPM Newsletter No. 4 – June 5, 2015
Click on photos to enlarge.

STRAWBERRY INSECT ACTIVITY LOW

Recent Rains Increase Fungus Disease Risk

Vegetable and Berry Growers Twilight Meeting
Thursday, June 11, 2015 at 5:30 p.m.
Snell Family Farm, 1000 River Road, Buxton, Maine 04093

Situation: Some much needed rain this week should help size up strawberries as we move toward harvest season. A few ripe berries are being reported from day-neutral strawberry beds on plastic mulch this week, but in general it looks as though our season should be about on a “normal” time span this summer. Lots of fields are expected to open around the 19th of June or soon after, in the southern and mid-state regions. The pest situation has remained pretty calm, although the recent rains should put growers on alert for possible fruit rot infections.

Strawberry bud weevil or “clipper” activity has become a bit more prevalent around the state this week, although many fields are now beyond the development stage were clipper can present a serious threat. Only a couple of fields exceeded the threshold (more than 1.2 clipped buds per two feet of row) in later ripening varieties. Raspberry and blackberry growers should be alert. Clipper will also move onto these plants to lay eggs and clip buds once the strawberries have gone into bloom. Brigade® and Sevin® are currently registered to control clipper in bramble crops.

Clipper Beetle on Strawberry Blossom

Clipper Beetle on Strawberry Blossom, photo by David Handley

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug activity has been very low this week. Several growers have sprayed fields, based on the appearance of nymphs last week, but there have been no fields over threshold in our scouting this week. Tarnished plant bug is a threat throughout the bloom and petal fall stage. Scout regularly for the small, yellow-green nymphs on the flower clusters and developing fruit. The threshold for nymphs is 4 or more flower clusters infested per 30 sampled. Insecticide options include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Two-spotted spider mites: The recent rains and cool temperatures have slowed development of two spotted spider mites this week. Although a couple more fields were found to have mites, only one was over threshold, and this was a field that had been under row covers. Mite populations can increase suddenly if warm dry conditions return, so continue to scout for them regularly.

White grubs: We’ve had a couple more calls this week from growers regarding white grubs feeding on the roots of strawberry plants. These are the larvae of scarab beetles, including Japanese beetles, Asiatic garden beetles and European chafers. Unlike the strawberry root weevil and black vine weevil larvae, these grubs have legs and a swollen back end. White grubs are starting to pupate now, and adults will begin to emerge shortly. A new generation of grubs will appear during the late summer and fall. Soil drenches with Admire Pro® or Platinum® can provide control of grubs in new plantings or following renovation in older plantings. Parasitic nematodes may also be applied. See the New England Small Fruit Management Guide for details.

Slug on Strawberry

Slug on Strawberry, photo by James Dill

Slugs may be a problem in some fields this season; although they tend to be worse in wet springs, especially if they follow a wet fall. Moist conditions and thick mulch tend to encourage the presence of slugs. Slugs usually feed at night, leaving large holes and tunnels in ripening fruit. Baits such as Deadline® and Sluggo® offer some control of slugs, but should be used prior to fruit ripening. Pay close attention to label instructions and precautions. Baits should also be applied to the fields in mid-September if slugs have been a problem, to reduce egg-laying.

Diseases: The recent rains will encourage the release of botrytis spores from overwintering sites (e.g. dead leaves), so fields now in bloom should be protected against infection with a fungicide spray. Although dry conditions earlier have likely saved many growers from having to apply an earlier fungicide spray, typically two to three sprays during the bloom period are needed to provide good protection against the development of gray mold.

Powdery mildew: The recent cool weather seems to have slowed the development of powdery mildew in strawberry fields, although early symptoms are being observed in some fields. Mildew often first appears as purplish blotches or streaks on the leaf and flower stems; but it is often first noticed by the more obvious symptom of an upward curling of the leaves and white, powdery growth on the undersides. Check your fields for leaf cupping now. Some, but not all, of the fungicide products registered for gray mold will also provide control of powdery mildew. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet Oil® are registered to control powdery mildew.

Leaf Spot on Strawberry Plant

Leaf Spot, photo by David Handley

Leaf spot and leaf scorch infections are becoming more apparent in most strawberry fields this week. Some fungicide materials registered for these foliar diseases will also provide control of gray mold, including captan, Topsin-M®, and Pristine®.

Leather rot (Phytopthora cactorum) could be a concern in fields which had long periods of standing water following the recent rains, especially if the fields were not mulched last fall. Fungicides applied for gray mold are generally not effective for leather rot. Foliar sprays of Aliette®, Agri-Phos® or Phostrol® applied during bloom or fruit development can help prevent this disease.

Reminder: Twilight Meeting
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at the Snell Family Farm in Buxton on Thursday, June 11 at 5:30 p.m.  John and Ramona Snell will host a tour of their farmstand, greenhouses and vegetable fields and describe their growing and marketing practices. In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year. We anticipate that one pesticide applicator recertification credit will be awarded for the meeting.

Snell Family Farm is located on Route 112 in Bar Mills (officially 1000 River Road, Buxton, ME 04093). Their phone number is 207.929.6166 and email address is info@snellfamilyfarm.com. Their web address is http://snellfamilyfarm.com/map.html.

DIRECTIONS

From Biddeford and Saco: Follow North Street (Route 112) ten miles north, one mile past Tory Hill.

From Portland: Take Route 22 (Congress Street) west about fifteen miles.  At the first stop sign you come to (where Route 22 veers right) go straight ahead on Portland Road. Cross Route 202 onto 4A by the hardware store across from the funeral home. Turn right on to Route 112.  Go a half mile north on Route 112 to the farm.

From Windham and Gorham: Take Route 202 west into Buxton (go straight through rotary on Route 202).  Turn right onto 4A at the hardware store. Turn right again at the intersection with Route 112.

From Sanford:  Take Route 202 east, turning left at Tory Hill Corner at the intersection with Route 112. Follow Route 112 north one mile to the Snell Farm.

From Standish: Turn on to Route 22 at the four way stop near Bonny Eagle Middle School. Turn right on Route 112 near the Bonny Eagle Shopping Center. Follow Route 112 south along the Saco River until you come to the farm.

Please note that Route 22 veers west and becomes Long Plains Road. Folks driving from Portland should stay straight onto Portland Road.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME 04259          Orono, ME 04473
207.933.2100                           1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 3 – May 28, 2015

Friday, May 29th, 2015

StrawberriesStrawberry IPM Newsletter No. 3 – May 28, 2015

Click on photos to enlarge.

STRAWBERRY INSECT PESTS NOW ACTIVE

Clippers, Tarnished Plant Bugs and Spider Mites Over Threshold this Week

Vegetable and Berry Growers Twilight Meeting
Thursday, June 11, 2015 at 5:30 p.m.
Snell Family Farm, 1000 River Road, Buxton, Maine 04093

Situation: Broad swings in temperature continue to characterize the weather, from unusually hot days to a surprise freeze in some inland towns last weekend.  Conditions also remain dry, and while that is good for reducing the chance of fungal diseases, the plants will need water soon to help size up the berries. Early varieties are at full bloom or slightly beyond in much of the state, while later varieties are now coming into bloom. Some fields may have experienced frost or freeze damage late last week as night temperatures fell dramatically, in spite of fairly windy conditions.

Strawberry bud weevil or “clipper” activity is increasing in some of the fields we’ve scouted. Clipped buds on later varieties are becoming apparent and were over the threshold (more than 1.2 clipped buds per two feet of row) in one location this week. Scout for clipped buds now in fields just coming into bloom. Once a field is in full bloom, clipper is no longer a significant threat. Insecticide options for clipper include Lorsban®, Brigade®, Bifenture®, Danitol®, Sevin® and PyGanic®.

Clipper Damage on Strawberry Plant

Clipped Flower Buds from Strawberry Clipper, photo by David Handley

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug activity has increased this week. We are now finding the small, yellow-green immature bugs, or nymphs, in the flower clusters. These will feed on the receptacle of the flowers, causing the fruit to have seedy ends, or “catfacing”. The nymphs are very small (2 mm) at this time and can be hard to see. It is important to scout any flowering fields for them now, as they can spread very quickly. The threshold for nymphs is 4 or more flower clusters infested per 30 sampled. Insecticide options for tarnished plant bug include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mites are building up in some fields, which is to be expected when we have extended warm, dry weather. Two fields have been over the control threshold of 25% or more of leaves infested. Mites will reproduce rapidly if warm conditions continue, so it is important to scout for them regularly. Chemical control options for two-spotted spider mites include Acramite®, Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, and Thionex®. Be sure to use enough liquid and pressure in the spray to get good coverage on the undersides of the leaves.

Root Weevils:  Two fields with a history of strawberry root weevil problems have had some grub activity this week. Infested plants look weak, and often wilt. There are no chemical controls registered for use within the harvest period at this point. Parasitic nematodes may be applied, but need high moisture conditions to become established and provide effective control. See the New England Small Fruit Management Guide for details.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by David Handley

Strawberry rootworm (not root weevil) adults and feeding injury have been found on strawberry leaves in some fields this spring. The adult stage of this insect is a small (1/8”) dark brown beetle. The beetles feed on strawberry leaves during the spring and late summer, causing numerous small holes in the leaves. The adults in fields now will soon lay eggs. The larvae are small grubs that feed on the roots of strawberry plants, causing them to be stunted and weak. If these beetles and/or feeding injury is prevalent in a field, a treatment is recommended. Sevin 50WP® is registered for control of this pest, and sprays targeted at other insect pests at this time may also control rootworm. Avoid spraying insecticides, especially Sevin 50WP®, during bloom, as it is highly toxic to many pollinating insects. Strawberry rootworm should not be confused with root weevil, a larger insect that causes much more serious damage when present in a field.

Spittlebug

Spittlebug, Photo by David Handley

Spittlebugs:  The frothy spittle masses on the leaf and flower stems from spittlebugs usually show up around bloom. Spittlebugs don’t pose a significant threat to the plants, but the spittle masses are a nuisance for pickers. Spittlebugs overwinter as eggs and the nymphs emerge in late May. Scouting for spittlebugs should start when the plants are at 10% bloom. Randomly inspect five, one square foot areas per field every week. Spread the leaves and inspect the crowns, leaf bases, leaf stems, and flower stems looking for the frothy spittle masses. Small, yellow-orange nymphs will be under the spittle. If the average number of spittle masses is more than two per foot, a treatment may be warranted. Spittlebugs tend to be a greater problem in weedy fields. Pesticides currently registered for spittlebug control include Provado®, Thionex®, Danitol® and Brigade®.

Diseases:  Fields in bloom should be protected against infection by spores of the gray mold fungus, Botrytis cinerea. Although the present dry conditions will likely reduce disease pressure this spring, fungicides need to be applied as protectants in case a significant moisture event occurs, causing a sudden release of fungal spores. Registered products include Topsin-M®, captan, Elevate®, Thiram®, Pristine®, Scala® and Switch®.  See the New England Small Fruit Management Guide for details.

Powdery mildew:  This foliar disease is now starting to show up on susceptible varieties. It may first appear as purple or red blotches on the leaf and flower stems. The most prominent symptom is an upward curling of the leaves and white, powdery growth on the undersides. Check your fields for leaf cupping now. Some, but not all, of the fungicide products registered for gray mold will also provide control of powdery mildew. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet Oil® are registered to control powdery mildew.

Leaf spot infections are becoming more common in strawberry fields this week. The spots usually appear on older leaves first, as small purple or red spots with white centers. Leaf scorch may also be seen. The spots are smaller in the case of scorch, and lack the white centers. Spots may coalesce to turn the leaves purple and brown, leading to the death of the leaf and weakening of the plant. Many strawberry varieties have at least partial resistance to leaf spot and leaf scorch. Fungicides registered for leaf spots include captan, Topsin-M®, Cabrio®, and Pristine®.

Grass control in strawberry fields:  Controlling perennial grasses in strawberry beds can be challenging. Poast®, Select 2EC® and Selectmax® 0.97EC are registered to control emerged grasses in strawberries. Often more than one application is needed to obtain satisfactory control. All of these products require the addition of a crop oil concentrate to the spray. It is important to note that these products can cause significant injury to strawberry plants if they are applied on hot, humid days, or if high temperatures occur within one or two days of application. Poast® should not be applied within 7 days of harvest. Select® and Selectmax® should not be applied within 4 days of harvest. Follow all product label instructions.

Reminder: Twilight Meeting
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at the Snell Family Farm, 1000 River Road, Buxton, ME 04093 on Thursday, June 11 at 5:30 p.m. The Snell’s will host a tour of their farmstand, greenhouses and vegetable fields and describe their growing and marketing practices. In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year. We anticipate that one pesticide applicator recertification credit will be awarded for the meeting.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against other products with similar ingredients.  Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 2 – May 20, 2015

Friday, May 22nd, 2015

StrawberriesStrawberry IPM Newsletter No. 2 – May 20, 2015

Click on photos to enlarge.

STRAWBERRY PESTS OFF TO A SLOW START

No Clippers, Tarnished Plant Bugs or Spider Mites Over Threshold this Week

Vegetable and Berry Growers Twilight Meeting
Thursday, June 11, 2015 at 5:30 p.m.
Snell’s Family Farm, Buxton, Maine

Situation: It’s too hot, no wait, it’s too cold.   Great swings in temperature have been the feature this spring as we bounce from days in the 80’s to days in the 40’s, but as far as strawberry plant development is concerned most fields are about where they should be for this point in the season.   Early varieties are coming into bloom, while later varieties now have flower buds emerging from the crowns. Some inland locations have had to protect buds from frost, and may have to again over the next week; while more southern and coastal sites have, so far, not had serious frost threats.  The most common complaint among growers is the lack of rain.  While ground water levels are still in good shape for irrigation, dry fields can lead to stressed plants and nutrient deficiencies, which result in poor fruit size and quality. Once the fruit have started to develop, strawberry plants should receive one to two inches of water per week to prevent a rapid decline in fruit size after the first picking.

Twilight Meeting
The University of Maine Cooperative Extension and the Maine Vegetable and Small Fruit Growers Association will hold a twilight meeting at Snell’s Family Farm in Buxton on Thursday, June 11 at 5:30 p.m.  John, Ramona and Carolyn Snell as well as other family members grow mixed vegetables, apples, bedding plants, cut flowers, and raspberries.  They sell their produce at their farmstand and at local farmers markets in addition to operating a large Community Supported Agriculture (CSA) program. The Snell’s will host a tour of their farmstand, greenhouses and vegetable fields and describe their growing and marketing practices.  In addition, we’ll discuss the upcoming season and pest management issues facing vegetable and berry growers this year.  We anticipate that one pesticide applicator recertification credit will be awarded for the meeting. Hold the date! We’ll give driving directions soon.

Strawberry bud weevil or “clipper” is now active in most of the fields we’ve scouted.  But so far all we have seen is feeding signs on a few open primary flowers, no clipped buds, suggesting that the adults are now just feeding on pollen and mating.  However, they will very soon start laying eggs and girdling flower buds. Given these signs, you should now start looking for clipped buds. Insecticide options for clipper include Lorsban®, Brigade®, Bifenture®, Danitol®, Sevin® and PyGanic®.

Clipper Injury

Clipper Injury, Photo by David Handley

Tarnished Plant Bug Nymph on Strawberry Blossom

Tarnished Plant Bug Nymph on Strawberry Blossom, photo by David Handley

Tarnished plant bug activity has been very low so far this season.  We have had reports of a few adults spotted in the field, but we have not yet found any nymphs, which are the more damaging stage of this insect.  The nymphs can be hard to find, especially if the plants are wet. Young nymphs are very small (2 mm), active, yellow-green insects.  It is important to scout for them regularly, as they can appear very quickly. The threshold for nymphs is 4 or more flower clusters infested per 30 sampled. Start scouting any field with open flowers now.  Insecticide options for tarnished plant bug include malathion, Assail®, Brigade®, Bifenture®, Danitol®, and PyGanic®.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mites have only been found in one location this week.  This is surprising given how dry it has been.  Mites typically proliferate under hot, dry conditions, and we often first find them in plantings under row covers.  But plantings that harbored a high mite population last fall are also likely to see a problem with mites in the spring.  Spider mites will reproduce rapidly under warmer temperatures, so it is important to scout for them regularly. If 25% of leaves sampled (e.g. 15 out of 60) have any mites, a spray should be applied. Chemical control options for two-spotted spider mites include Acramite®, Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, Thionex® and JMS Stylet Oil® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).  Be sure to use enough liquid and pressure in the spray to get good coverage on the undersides of the leaves.

Cyclamen mites:  We have seen two fields with light symptoms of cyclamen mite injury this week.  Infested plants show weak growth and yellow, crinkled leaves. These mites are very small and reside in the crown of the strawberry plant, feeding on the developing leaves and flower buds. They are very hard to see, even with magnification. Portal®, Kelthane® or Thionex® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside.   Thionex® will no longer be available for use on strawberries after July of 2016.

Cyclamen Mite Damage on Strawberry Plant

Cyclamen Mite Damage on Strawberry Plant, photo by David Handley

White Grub

White Grub, Photo by David Handley

White grubs:  There have been calls regarding white grubs in turf this week, so we should expect that we may also see injury in strawberry beds.  Infested plants are stunted and often wilt during the heat of the day. These grubs are the larvae of the Japanese beetle, European chafer and Asiatic garden beetle. They have legs and a swollen anterior (rear end).  Admire Pro® can be applied for control of white grubs in the spring.  It should be applied within two hours of irrigation or rainfall to be sure the chemical gets into the root zone, and it requires a 14-day pre- harvest interval.

Diseases:  As the fields come into bloom it is time to protect the flowers against infection by spores of the gray mold fungus, Botrytis cinerea. Fruit infections take place through the flowers, so gray mold control efforts must be focused on the bloom period.  Two to three sprays of fungicide are typically required to provide good protection. The first spray is usually applied at 5-10% bloom, followed by a second application at petal fall.  Additional applications may be applied if there is significant rainfall between or following these two sprays.

Leather rot (Phytopthora cactorum) may become a problem in fields where standing water is common during bloom and fruit development, especially if the fields were not mulched last fall. Incidence of leather rot can be reduced by applying straw mulch between the rows to prevent berries from touching the soil and reducing soil splashing onto the berries.  Foliar sprays of Aliette®, Agri-Phos® or Phostrol® may be applied during bloom and fruit development to prevent leather rot when there has been excess moisture in a field, especially those with a history of this problem.

Powdery mildew:  We have not yet seen symptoms of this fungus disease in fields.  It tends to be more prevalent under warm, humid conditions. It may first appear as purple or red blotches on the leaf and flower stems. Later, upward curling leaves and white, powdery growth on the undersides of the leaves becomes evident. Check your fields for pinkish purple leaf and flower stem lesions as new leaves emerge. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet Oil® are registered to control powdery mildew.

Angular Leaf Spot

Bacterial Angular Leaf Spot, Photo by David Handley

Angular leaf spot is a bacterial disease characterized by small water-soaked spots on the leaves, which may turn yellow or black. The symptoms start on the lower leaves but spread throughout the foliage when spores are splashed up by rain or irrigation water. Infections can cause blackening of the berry stems and caps. This disease is favored by extended cool, wet weather with night temperatures close to freezing. Irrigating fields for frost protection encourages development and spread of the disease. Hydrogen dioxide (OxiDate®) may have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

Sincerely,

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating.  Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment.  A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

Strawberry IPM Newsletter No. 1 – May 8, 2015

Friday, May 8th, 2015

StrawberriesStrawberry IPM Newsletter No. 1 – May 8, 2015

Click on photos to enlarge.

2015 STRAWBERRY PEST MANAGEMENT SEASON BEGINS

Long, Cold Winter Delays Early Spring Growth

Situation:
A long cold winter has suddenly departed and warm temperatures are now moving strawberry growth along very rapidly. Most fields had adequate snow cover to prevent serious winter injury, but we expect some fields may start showing symptoms as the plants start to flower. Cutting into the crowns of injured plants will reveal dark brown discoloration in the internal tissue. Helping plantings recover from winter injury involves compensating for the damaged vascular system. Make sure the plants get plenty of water, especially in this dry period; and it may help to apply extra nutrients to encourage root growth and recovery, including nitrogen, calcium, and phosphorus. While we do not recommend heavy nitrogen fertilizer applications in the spring, up to 20 pounds of actual N (e.g. 125 lb. calcium nitrate) may improve early spring growth. Warmer temperatures will also increase insect activity. We have heard early reports of both strawberry clipper and tarnished plant bug.

2015-2016 New England Small Fruit Management Guides are available at Highmoor Farm. The guide contains the latest information on management options for small fruit pests as well as cultural information. Cost of the guide is $13.00 plus $2.69 postage for a total of $15.69.

To order the guides, please send your check made payable to UMaine Cooperative Extension mailed to: Highmoor Farm, P.O. Box 179, Monmouth, Maine 04259, attention Pam St. Peter. For more information, contact Pam St. Peter at 933.2100 or pamela.stpeter@maine.edu.

Members of the Maine Vegetable and Small Fruit Growers Association (MVSFGA) or the New England Vegetable and Berry Growers Association receive free copies of the guide. For MVSFGA membership information, contact Bill Jordan at 799.1040.

We will begin scouting strawberry fields for major insect pests within the next two weeks, including volunteer farms in North Berwick, Wells, Cape Elizabeth, Poland Spring, New Gloucester, Dresden, Monmouth, Wayne, and Farmington, and will be reporting our findings through this newsletter and blog on a weekly basis until harvest time. You can also get quick access to this information on the Pest Management web page at http://umaine.edu/ipm/.

The best way to manage strawberry pests is to scout your own fields regularly and often. You should start scouting regularly as soon as flower buds emerge from the crown. You should be able to identify the major pests and their damage, and be able to determine if control measures are necessary. To properly scout your fields you may want a copy of the Strawberry Production Guide for the Northeast, Midwest and Eastern Canada. This contains detailed information on strawberry pest identification and monitoring, and also provides information on all other aspects of strawberry production. It may be purchased for $45.00 per copy from the University of Maine Cooperative Extension online.

Clipper Beetle on Strawberry Bud

Clipper Beetle on Strawberry Bud, photo by James Dill

Strawberry bud weevil or “clipper” will become active as flower buds begin to emerge. We have had reports of clipper activity within other New England states and in southern Maine. The clipper is a small weevil, which girdles strawberry flower buds, causing them to dry up and fall off the flower stalk. Scout for damage by counting the number of clipped buds in two feet of row length at five different locations in a field. If the average number of clipped buds per two-foot sample exceeds 1.2, or if live clippers are found, control measures are recommended. Damage is usually first noticed at the edges of the field. Border sprays may be effective in keeping this insect from becoming a problem in larger fields. Fields with a history of clipper problems will typically exceed threshold nearly every year. Insecticide options for clipper include Lorsban®, Brigade®, Sevin® and PyGanic®.

First Instar Tarnished Plant Bug Nymph

First Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bugs adults have been reported in southern Maine, indicating that they will soon be laying eggs. Strawberries are one of their preferred hosts at this time of year. Once the eggs start to hatch, we’ll find the nymphs feeding in the flowers. The nymphs are small, active, yellow-green insects. It is important to scout for them regularly, as they can appear very quickly in warm weather. Tarnished plant bugs feed on the open strawberry flowers, causing the berries to have seedy ends. To scout for the nymphs shake 30 flower clusters (six clusters in five different locations) over a plate. If four or more of the clusters out of the 30 sampled have any nymphs, control measures should be taken. Be on the alert and scout your fields now! Insecticide options for tarnished plant bug include malathion, Brigade®, Danitol®, and PyGanic®.

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

Cyclamen mites: Plants showing weak growth and yellow, pinkish or blackened, crinkled leaves may be infested with cyclamen mite. Cyclamen mites are very small, smaller than spider mites, and reside in the crown of the strawberry plant feeding on the developing leaves and flower buds. They are very hard to see, even with magnification. Infested plants have shrunken distorted leaves and flower stalks, and produce few, if any, marketable fruit. Miticides such as Kelthane® and Portal® can be effective, but must be applied in lots of water to be sure that the material is carried down into the crowns where these mites reside. Thionex® may also be used, but registration of this product on strawberries will run out in July of 2016.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Two-spotted spider mites have not yet been a problem this spring, but growers with plants under row covers should be alert. This is often where we first find mite problems. Spider mites will reproduce rapidly when warmer weather arrives, so it is important to scout for them regularly. Spider mites feed on the undersides of strawberry leaves, rasping the plant tissue and sucking the sap. Infested leaves will develop yellow flecking and a bronzed appearance. The plants become weakened and stunted. Fields that have had excessive nitrogen fertilizer and/or row covers tend to be most susceptible to mite injury. To scout for mites, collect 60 leaves from various locations in the field and examine the undersides for the presence of mites. Mites are very small – you may need a hand lens to see them. Chemical control options for two-spotted spider mites include Acramite®, Portal®, Nealta® Savey®, Zeal®, Vendex®, Oberon®, Brigade®, Danitol®, Thionex® and JMS Stylet Oil® (oils will cause plant injury if used in combination with captan or within 14 days of an application of sulfur).

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

Root weevil management
Fields that were infested with root weevils last summer should be inspected for grubs this spring. Infested plants appear week and stunted, usually in somewhat circular patches in a field. Digging under the plants will reveal small (1/4”-1/2”) crescent-shaped legless grubs. Typically, the grubs begin to pupate when the plants are in bloom. A soil drench of Platinum® (thiamethoxam) insecticide during the spring and/or fall when the grubs are active in the soil can provide control. However, Platinum® has a 50 day pre-harvest interval, so it is too late for applications in most fruiting fields this year. Platinum® may also be used as a pre-plant or planting treatment for root weevils. It is not too late to put on an application of nematodes to control the grubs (optimal timing is about mid-May). Two species of nematodes appear to offer the best control of root weevil grubs. Heterorhabditis bacteriophora (Hb) appears to be the best candidate for control of root weevils when the soil temperature is above 60 degrees, and is available from Green Methods, the Integrated Biocontrol Network, and Koppert Biological Systems.

Nematodes are living organisms and they can be killed if they are misapplied. Order nematodes ahead of time and be ready to apply them through a sprayer or irrigation soon after they arrive. Refrigerate them if you cannot apply right away. Do not apply nematodes using a sprayer with a piston pump. Use clean equipment, removing all screens finer than 50-mesh. Apply nematodes in early morning or evening in a high volume of water to already moist soil, pre-irrigating if needed. Apply another ¼ inch of irrigation after application to wash them onto and into the soil. Researchers and suppliers recommended 250 (if banded in the row) to 500 million per acre, at a cost of $100-$200 per acre depending on volume and source. Nematodes tend to work best in heavily infested fields. Strawberry plants can recover their vigor remarkably well if crown feeding has not occurred and diseases haven’t taken over the roots.

Once the adults become active in July, bifenthrin (Brigade®) will provide some control if used at the highest labeled rates. The best timing for this spray is at night during the peak feeding activity of adults, before they start laying eggs, or about the time harvest ends.

White Grub

White Grub, Photo by David Handley

White grubs: Weak growth noted in fields this spring may also be the result of white grubs feeding on the roots of newer plantings. These grubs are the larvae of beetles, including European chafer and Asiatic garden beetle. They differ from the larvae of black vine weevil and strawberry root weevil in that they have legs and a swollen anterior (rear end), and they tend to be larger. Their feeding weakens the plants by reducing the number of roots. The grubs can be found by pulling up weak plants and sifting through the soil that surrounded the roots. Controlling white grubs once they have become established in a field can be difficult. These tend to be more of a problem in new fields that have been planted following a grass rotation crop, because the adults prefer to lay their eggs in sod. Admire Pro® and Platinum® insecticides are labeled for control of white grubs and should be applied within two hours of irrigation or rainfall to be sure the chemical gets into the root zone. Admire Pro® requires a 14 day to harvest interval, while Platinum® requires a 50 day pre-harvest interval.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Diseases: Bloom is a critical time to protect strawberry fruit against gray mold caused by the fungus Botrytis cinerea, especially when conditions have been damp. Two to three sprays of fungicide during bloom are typically required to provide good protection against this disease. If you tank mix insecticides and fungicides, avoid spraying when bees are active. Botrytis cinerea overwinters on old leaves and plant debris. Fruit infections take place almost exclusively through the flowers, so gray mold control efforts must be focused on the bloom period. If the bloom period is dry and/or good fungicide coverage is maintained, incidence of gray mold at harvest should be low.

There are several excellent fungicide choices for control of gray mold in strawberries. Elevate® (fenhexamid) has good to excellent activity against Botrytis. Captevate® is a pre-mix of captan and fenhexamid and has a broader spectrum of activity than Elevate® alone. Switch® (cyprodinil and fludioxonil), Scala® (pyramethanil) and Pristine® (pyraclostrobin and boscalid) are also excellent products for gray mold control. Topsin M® + captan is also a good fungicide combination, but remember that captan is strictly a protectant and can be washed off by rain or irrigation water. Thiram is similarly effective but also susceptible to wash-off.

The fungicides Cabrio® (pyraclostrobin) and Abound® (azoxystrobin) are NOT suitable for gray mold control, but are effective against anthracnose and other fruit rot and leaf spot diseases. All fungicides mentioned above have a 0-day pre-harvest interval, except Topsin M® (1 day) and thiram (3 days). Remember to alternate fungicides with different modes of action for resistance management purposes.

Red Stele Symptoms on Strawberry Plant

Red Stele Symptoms on Strawberry Plant, photo by David Handley

Red stele root rot
Although early spring conditions have not been especially conducive to red stele development, you should still be alert for this root rot if any fields appear to be weak, stunted or dying. To diagnose red stele, pull up a few plants that look weak and scrape the roots of these plants to see if the center of the root, known as the stele, is rusty red in color, instead of the normal white. The red color would indicate an infection. Red stele is caused by Phytophthora fragariae, a soil pathogen that infects roots when soils are wet with temperatures around 50°F. The pathogen grows into the roots causing the plants to become weak, stunted and to eventually die. Symptoms are most evident in the spring, and can be mistaken for winter injury. Ridomil Gold®, Alliette® or Phostrol® are fungicides that can be applied in the late fall or early spring for control of red stele. Many varieties have some level of resistance to the disease, but the most effective management strategy is to plant only into well-drained soils, and/or plant onto raised beds.

Powdery Mildew

Powdery Mildew, photo by David Handley

Powdery mildew: This fungus disease may first show up as purple or red blotches on the leaf petioles and flower stems in strawberry fields. Most of us are more familiar with the later symptoms of upward curling of the leaves and white, powdery growth on the undersides of the leaves. Check your fields for pinkish purple leaf and flower stem lesions as new leaves emerge. Pristine®, Cabrio®, Topsin-M®, captan, Procure®, Torino® and JMS Stylet Oil® are presently registered to control powdery mildew.

Angular leaf spot is a bacterial disease that is characterized by translucent leaf spots that may turn yellow and eventually black. The symptoms tend to start on the lower leaves but may move upwards as bacterial spores are splashed up by rain or irrigation water. Infection of the calyxes may result in a blackening of the berry stems and caps, reducing their marketability. Bacterial angular leaf spot is favored by extended cool, wet weather and nights with temperatures close to freezing. Frequent irrigation for frost protection can greatly encourage the development and spread of the disease, as will extended cool, damp weather. Susceptibility to this disease appears to vary significantly between varieties. The copper-containing material Kocide®, can reduce the spread of this disease. Start spray applications before bloom to prevent multiplication of the bacteria on the leaves before they jump to the berry caps. Application of copper sprays after bloom can result in fruit injury and is not recommended. Hydrogen dioxide (OxiDate®) may also have some activity against angular leaf spot when used on strawberries as part of a gray mold management program.

Other Berries:

Raspberries are showing both significant winter injury and cane breakage from snow in many fields. I expect even more winter injury to become apparent once the floricanes start to flower. Tip dieback often occurs due to winter damage to the vascular tissue within the canes. Strawberry clipper will also attack raspberry blossoms, so keep an eye out for this insect once flower buds emerge.

Highbush blueberries are also showing significant winter injury in some fields. Dark brown or black discoloration of last year’s shoot growth, and/or shriveling of the shoot tissue indicate winter injury and desiccation, frequently resulting in death of the flower buds. Cane breakage from heavy snow loads is also common in fields. Mummy berry spores are starting to be active in southern and coastal Maine. Expect infection periods to occur over the next few weeks, anytime there is a significant moisture event (rain, mist, fog). Protectant fungicides for mummy berry include Indar®, Orbit®, and Quilt Excel®.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Ave
Monmouth, ME 04259         Orono, ME 04473
207.933.2100                          1.800.287.0279

Maine Cooperative Extension, the Land Grant University of the state of Maine and the U.S. Department of Agriculture Cooperating. Cooperative Extension and other agencies of the U.S.D.A. provide equal opportunities in programs and employment. A Member of the University of Maine System.

Where brand names or company names are used it is for the reader’s information. No endorsement is implied nor is any discrimination intended against other products with similar ingredients. Always consult product labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

 

Strawberry IPM Newsletter No. 6 – July 16, 2014

Wednesday, July 16th, 2014

Strawberries

Strawberry IPM Newsletter No. 6 – July 16, 2014

Click on photos to enlarge.

RENOVATION AND WEED MANAGEMENT ISSUE

Time to Get Your Strawberry Beds Ready for Next Year

Be Ready to Manage Pests in Day-Neutral Strawberries

A cold, nearly snowless period in late December to early January resulted in some moderate winter injury to many strawberry fields around the state this spring.  But favorable spring growing conditions with little to no frost issues resulted in a pretty good crop in most fields. Weather conditions for the harvest seemed often too hot or rainy, especially during the all-important weekends, but customer demand was strong throughout the relatively short season. Pest pressure in most fields was pretty light throughout the season. Insects, including tarnished plant bug and strawberry bud weevil or clipper appeared fairly late and often in low numbers. While spider mites were hardly an issue, cyclamen mites were present in many fields, causing yellowing and dwarfing of affected plants. Root weevils and white grubs were an issue in some fields, especially where problems had been observed last year. Applications of both soil insecticides and parasitic nematodes appear to have helped reduce the problem in most situations. Disease pressure was also light in most fields. Timely fungicide sprays kept gray mold to a minimum, and foliar diseases, such as powdery mildew and leaf spot only began to show up towards the end of the season.

Don’t forget about your strawberries after harvest. Follow the recommended renovation steps listed below for matted row strawberries as soon after harvest as possible; and continue to scout for and manage disease, insect and weed problems as they arise. Some of the more common issues to be alert for during the summer are listed below.

DISEASES:  Foliar diseases should be monitored in your fields by regularly examining leaves. All of the common leaf diseases were present in fields this spring and we should expect that they will continue to be a problem through the summer. The most common summer diseases are powdery mildew, leaf spot and leaf scorch. Fungicides available for these diseases include captan, Topsin-M®, Cabrio®, and Pristine®. See the New England Small Fruit Management Guide for detailed descriptions of these diseases and their management.

Powdery Mildew

Powdery Mildew, photo by David Handley

Leaf Spot

Leaf Spot, photo by David Handley

Black root rot is a disease complex which can be brought on by a combination of problems, including nematodes, soil fungi (Rhizoctonia, Pythium), herbicide carryover, and soil compaction. Plants become weak and may wilt and die. Roots on affected plants are black and poorly developed. This tends to be a problem in fields that have been in strawberries constantly for many seasons, and in fields that are under stress in other ways, such as winter injury. Rotating fields to crops other than strawberries for at least three years is an important management strategy for black root rot. Improving soil drainage and breaking up hardpans in the soil may also help. Pre-plant root dips with azoxystrobin (Abound®) may also reduce incidence of black root rot in some fields.

INSECTS:  If black vine weevils or strawberry root weevils are a problem in a strawberry field that you would like to carry over, bifenthrin (Brigade®, Bifenture®) can be applied when adult feeding is noticed (usually until mid-late July). Look for notching along the leaf edges and the presence of the black or brown snout beetles. Applications should be made at night when these insects are active, and the highest rate of the insecticide should be used. For control of the grubs a soil drench of Platinum® (thiamethoxam) insecticide should be applied during the fall and/or early spring when the grubs are active in the soil. This product has a 50 day pre-harvest interval and may also be used as a pre-plant or planting treatment for root weevils. Parasitic nematodes such as Heterorhabditis bacteriophora or Steinernema feltiae can also be applied to provide control of root weevil grubs in late August. Nematodes require specialized handling and application. Contact us or talk with one of the suppliers for more details. See the New England Small Fruit Management Guide for sources.

Black Vine Weevil

Black Vine Weevil, photo by David Handley

Strawberry Root Weevil Grub

Strawberry Root Weevil Grub, photo by David Handley

White grubs have been an increasing problem in recent years.  The grubs may be the larvae of several species of scarab beetles, including June beetles, rose chafers, Japanese beetles, Asiatic garden beetles and European chafers. The beetles lay their eggs in June and July and the grubs feed on the roots of strawberries from July through mid September. Affected plants will be stunted and wilted and may die during dry periods. Pulling up plants reveals that roots have been chewed off about an inch below the soil line. Sifting through the soil below the plants may reveal the whitish crescent-shaped grubs which can range in size from 3/8 inch to almost 1 ½ inches long, with six legs near the head and a swollen rear-end. The two most effective periods to treat plantings for grubs are in the spring prior to when they pupate (May) and in the late summer when the next generation is actively feeding (late August). Materials should be applied with plenty of water to moist soil to be sure they reach the root zone. Materials currently registered for control of grubs include Platinum® and Admire Pro®. Parasitic nematodes can also provide control of grubs and should be applied with similar timing. Nematodes are very sensitive to ultraviolet light and dehydration and must be applied with lots of water. See the New England Small Fruit Management Guide for sources of parasitic nematodes.

Strawberry rootworm (not root weevil) is a small (1/8″) dark brown to black beetle which feeds on strawberry foliage, causing it to look skeletonized. The small larvae feed on strawberry roots, further weakening the plant. Adult feeding damage on the leaves usually occurs in late July through August. Heavy rootworm feeding weakens strawberry plants so control is warranted when injury is noticed.

Strawberry Rootworm Beetle

Strawberry Rootworm Beetle, photo by David Handley

Potato Leafhopper

Potato Leafhopper, photo by James Dill

Keep a lookout for potato leafhoppers, which can weaken strawberry plants and spread disease. The potato leafhopper does not overwinter in Maine, but must fly in from southern states. These small, bullet-shaped insects feed on plant sap from the undersides of leaves, causing the leaves to become curled, stunted and yellow-streaked. Symptoms are often first noticed in new strawberry plantings, but leafhoppers will also infest older plantings and a variety of vegetables, flowers and fruit crops. To scout for leafhoppers, brush the leaves of the plants with your hand. The small, whitish adults can be seen flying off the plant. Examine the underside of some injured leaves. Look for small, light green leafhopper nymphs. They are about 1/16 inch long. When touched, they will crawl sideways in a crab-like manner. Controls for potato leafhoppers include malathion, carbaryl or Provado®.

MITESTwo-spotted spider mites can increase significantly during the summer. Continue to take leaf samples for spider mites throughout the summer. If more than 25% of a 60-leaf sample has mites, controls should be applied. Summer is an ideal time to use predatory mites to control pest mites, because they prefer warm temperatures, and there is less chance of an insecticide spray that might kill them. Amblyseius fallacis can provide good control of two-spotted spider mites when they are released at a rate of about 10,000 mites per acre. Predator mite releases should only be made after a spider mite infestation has been found in the field. Releasing predators into a clean field will often result in them dying, due to a lack of food. See the New England Small Fruit Management Guide for sources of predatory mites.

Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley

Cyclamen Mite Damage

Cyclamen Mite Damage, photo by David Handley

Cyclamen mites:  Many fields were infested with these mites this spring, and summer may provide a good opportunity to control them. Plants showing weak growth and yellow, crinkled leaves may be infested with cyclamen mite. These mites are very small and reside down in the crown of the strawberry plant feeding on the developing leaves. They are very hard to see, even with magnification. Miticides such as Thionex®, Kelthane® or Portal® can be effective, but must be applied with lots of water to be sure that the material is carried down into the crowns.

WEEDS:  Weeds can become a big problem during the summer because they are often forgotten among all the other demands on our time and because of limited control options. However, the importance of good weed management should not be underestimated.  Keeping weeds under control this summer will prevent future infestations. Here’s a summary of weed control options for strawberries:

1.  Cultivation:  Following renovation, cultivation between strawberry rows can provide effective temporary control of annual weeds. Several types of cultivators are available which will work well in strawberry beds. Cultivators can also be used to help sweep runners into the plant rows.

2.  DCPA (Dacthal®):  A pre-emergent herbicide used in the early spring, late fall or after renovation. It offers good, short-term control of some annual broadleaf weeds and grasses. It is weak on ragweed, galinsoga, smartweed, shepherd’s purse and mustard. Its action will be improved if worked into the soil by irrigation or light cultivation, and it tends to work best in lighter, warmer soils. This may be used as an alternative to terbacil or napropamide when there is a high risk of plant injury from those products.

3.  Napropamide (Devrinol®):  A pre-emergent herbicide which provides good control of annual grasses, volunteer grains and some broadleaf weeds. It is typically applied just before mulching in the fall. Split applications have become popular due to the loss of other pre-emergent herbicides, e.g. half maximum rate application after renovation or in late summer after desired daughter plants have rooted, and a second half rate application once the strawberry plants are dormant. Napropamide should be activated by irrigation, rainfall or light cultivation within 24 hours of application. Repeated long-term use of this material, i.e. with no crop rotation, may eventually result in poor daughter plant establishment, due to rooting inhibition.

4.  Terbacil (Sinbar®):  An effective pre-emergent herbicide with some post-emergent activity, which should be applied at renovation time – after mowing and tilling the beds, but before new growth begins. A second application can be made in late fall, after the plants are dormant. No more than 6 oz. may be applied in a single application, and no more than 8 oz. may be applied in one season. An example of one season’s use could be 5 oz. applied at renovation and 3 oz. applied in the late fall, the latter in addition to napropamide or DCPA. Terbacil can cause injury to strawberry plants. It is important to determine appropriate rates for each location.

5.  Sethoxydim (Poast®): A post-emergent herbicide for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Do not use sethoxydim within 6 weeks of terbacil (Sinbar®) applications, to avoid leaf injury.  Sethoxydim should be used in combination with a crop oil concentrate. Do not tank mix with 2, 4-D.

6.  Clethodim (Arrow®, Prism®, Select®):  A post-emergent herbicide, similar in activity to Poastâ, for control of actively growing grasses. It will not control broadleaf weeds. It should not be applied when grasses are under stress, e.g. drought, or on unusually hot, humid days. Clethodim should be used in combination with a crop oil concentrate.

7.  Paraquat (Gramoxone Inteon®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Paraquat will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. It should be used in combination with a nonionic surfactant. Paraquat should not be applied within 21 days of harvest or more than three times in one season.

8.  Pelargonic Acid (Scythe®):  A contact herbicide for post-emergent control of most annual weeds and suppression of many perennial weeds. Scythe® will injure or kill strawberries, so applications are made between rows only, with a sprayer shielded to protect the strawberries. This product has a relatively low toxicity and no residual soil activity. It has a strong, unpleasant odor.

9.  2,4-D Amine (Formula 40®, Amine 4):  A post-emergent herbicide effective on most broadleaf perennial weeds. It will not control grasses, nor offer any pre-emergent control. 2,4-D should be applied immediately after harvest is complete if emerged broadleaf weeds are a problem. After application, the bed should be left undisturbed for three to five days, before mowing the leaves off the plants. This allows time for the material to be taken in by the weeds. This material can also be used when the plants are dormant (late fall or early spring) to control winter annuals and biennials. Fall applications may result in injury to the strawberries if the plants are not completely dormant. Do not tank mix 2,4-D with sethoxydim (Poast®).

10.  Flumloxazin (Chateau®):  A pre-emergent herbicide for control of broadleaf weeds, including dandelion and shepherd’s purse. For use in the fall when plants are dormant for control of weeds the following spring.

11.  Pendimethalin (Prowl H20®):  A pre-emergent herbicide that may be applied as a band with a shielded sprayer between the rows of strawberries. No weed control will be provided within the plant rows, and contact of this product on the strawberry plants will cause injury. May not be applied within 35 days of harvest.

The use of herbicides alone rarely gives complete weed control. Some hand weeding will be necessary. To provide good weed control throughout the life of a strawberry bed, growers should concentrate on crop rotation and good pre-plant weed control.

 

Strawberry Bed Renovation Review

Bed renovation should begin as soon after harvest as possible. The earlier the beds get renovated, the more time runner plants have to develop, which means larger crowns and more flower buds for next year. Early renovation also improves weed management by tilling in many weeds before they go to seed, and can help with insect and foliar disease control by interfering with life cycles at a critical stage of development. The first step in the bed renovation process is to determine which beds should be carried over for another year and which should be plowed down and put into a crop rotation. Beds that did not suffer much from winter injury, had good production and a good plant stand with no major weed, insect or disease problems should be carried over for another year. Beds that do not meet these criteria should be plowed down and seeded to a suitable cover crop to reduce weed, insect and disease problems that have developed, and to increase soil organic matter content. Ideally, beds that are plowed down should be rotated out of strawberries for at least three years. If properly managed, crop rotation will greatly reduce pest problems and improve the vigor and longevity of strawberry beds without the need for soil fumigation.

Renovating a strawberry bed is basically a thinning process to promote healthy new growth that can support a good crop next spring. While some parts of the following renovation scheme may be modified for individual situations, all beds should undergo the following steps once harvest is complete.

1.  Broadleaf weed control:  If perennial broadleaf weeds such as dandelion, shepherd’s purse, daisy or goldenrod are a problem and/or a high population of annual broadleaf weeds such as lambsquarters, sorrel or pigweed are present, hand-pull as many as possible, especially within the plant rows, and/or apply 2,4-D amine (Formula 40®).

Mowing Strawberry Leaves

Mowing Strawberry Leaves, photo by David Handley

2.  Leaf mowing:  Four to five days following the 2,4-D application (or immediately if 2,4-D was not applied) mow off the leaves of the strawberries about 1 ½ inches above the crowns. If the planting is weak, it is recommended that this step of the renovation process be skipped.

3.  Fertilization:  Apply 40 to 60 pounds of actual nitrogen per acre (use the higher rate on sandy soils and fields where growth has been weak). Phosphorus and potassium applications should be made according to soil test recommendations. Soil testing kits and information are available from your county Cooperative Extension office.

4.  Plant thinning:  For the single matted row system, strawberry plant rows should not be any wider than 24 inches. After mowing off the leaves, till the sides of the rows to narrow the beds back to a width of 12 to 18 inches. Use the wider setting for varieties that tend to throw few runners or any fields experiencing drought stress.  Set the tiller so that it incorporates the mowed leaves and spreads about one inch of soil over the remaining crowns at the same time. This will reduce leaf disease and mite problems, and help stimulate new root growth on the remaining plants.

5.  Pre-emergent weed control:  To control annual weeds, apply terbacil (Sinbar® 80WP) according to label directions (2 to 6 oz. per acre). Be sure to follow all label precautions. To avoid plant injury, do not use terbacil if you do not intend to mow off the leaves. Napropamide (Devrinol®) or DCPA (Dacthal®) may be used as an alternative to terbacil at this time, as described below. If you are not using herbicides, regular cultivation, before weeds are more than 2” tall, will be needed throughout the summer.

6.  Subsoiling:  Soil compaction caused by tractor and picker traffic in the field can cause soil drainage problems and interfere with good root development. Using a subsoiling blade between the rows will break up compacted layers of soil and improve water infiltration. Subsoiling is best done late in the renovation sequence to prevent interference from straw and crop residues.

7.  Irrigation:  To encourage rapid plant growth and get the most out of fertilizers and herbicides, irrigate the beds regularly. Strawberries will grow best if they receive 1 ½ inches of water per week during the growing season.

Don’t forget your plants once these renovation steps are completed. Check the strawberry fields regularly during the summer for pest problems. Finding and managing problems early can prevent major problems next spring. Pay close attention to the following items:

Strawberry Irrigation

Strawberry Irrigation, photo by David Handley

Sidedressed Strawberry Planting

Sidedressed Strawberry Planting, photo by David Handley

NUTRITION:  Following the application of 40 to 60 pounds of actual nitrogen at renovation, another 20 pounds of nitrogen should be applied in mid- to late-August to stimulate flower bud development. One way to determine the nutrient status of strawberry plants during the summer is to have a leaf tissue analysis done. Tissue analysis offers a view of what is happening within the plant, and can spot any nutrient deficiencies. In combination with regular soil tests, tissue analysis will provide a complete picture of a field’s fertilizer needs. For more information about tissue analysis contact the UMaine Analytical Lab, 5722 Deering Hall, Rm. 407, University of Maine, Orono, ME 04469-5722, telephone: 207.581.2945.

 

Pest Management for Day-Neutral Strawberries

Most of the important pests that damage June-bearing varieties can be as much or more of a problem on day-neutral types. Because day-neutral strawberries will have buds, flowers and fruit all occurring at the same time, it is critical to pay close attention to the required number of days to harvest after a pesticide application, to be sure you can safely harvest ripe fruit while still protecting buds and blossoms. Some of the more important pests are listed below, along with currently recommended pesticides and days to harvest as stated on current labels.

Male and Female Spotted Wing Drosophila Flies

Male (left) and Female (right) Spotted Wing Drosophila, photo by Griffin Dill. Actual size: 2-3 mm.

Spotted wing drosophila (Drosophila suzukii) is a new pest, which is likely to be a concern for day- neutral strawberries, fall raspberries and blueberries. This is a small fruit fly, similar to those that hover around the bananas in your kitchen. However, this species will lay its eggs on fruit before it ripens, resulting in fruit that is contaminated with small white maggots just as it is ready to pick. Infested fruit quickly rots and has no shelf life. This insect can complete a generation in under two weeks, with each adult female laying hundreds of eggs. Therefore, millions of flies can be present soon after the introduction of just a few into a field. Frequently repeated insecticide sprays (1 to 2 per week) may be needed to prevent infestations once the insect is present in a field. Spotted winged drosophila can successfully overwinter here, although it may not build up to damaging levels until late in the summer. We have set out monitoring traps for spotted winged drosophila in fruit plantings around the state to determine the activity of this pest in Maine. However, these traps may not provide adequate early warning, i.e. when we find them in a trap they are probably already established in the field. We have found just a few spotted wing drosophila in Maine over the past two weeks, but not yet in damaging numbers. Products that provide good control of drosophila on strawberries include Radiant®, Brigade®, Danitol®, malathion and Assail®. Keeping fields clean of over-ripe and rotten fruit will also help reduce the incidence of this insect. For more information on identifying spotted wing drosophila and updates on populations around the state, visit our SWD blog.  Other spotted wing drosophila resources can be found on the websites of Michigan State University, Penn State, and University of New Hampshire.

Large Tarnished Plant Bug Nymph

Third Instar Tarnished Plant Bug Nymph, photo by David Handley

Tarnished plant bug:  This is one of the most prevalent and persistent pests of day-neutral strawberries, because summer flowering coincides with peak populations of this insect. Adult and nymph stages feed on the flowers and developing fruit, causing them to have seedy ends and other malformations. Regular insecticide applications are often required to keep the damage in check. Scout the flower clusters for adults and nymphs often to determine if controls are necessary. Insecticide products for tarnished plant bug include:

Tarnished Plant Bug
Product Days to Harvest
Brigade® 0
Pyganic® 0
Assail® 1
Dibrom® 1
Rimon® 1
malathion 3
Two-spotted Spider Mites

Two-spotted Spider Mites, photo by David Handley


Two-spotted spider mites:  
Mites can become a problem during the summer when the growing conditions are warm and dry. In addition to infesting the leaves, mites can move onto the fruit, reducing marketability. Plants that are drought-stressed, over fertilized with nitrogen, or prone to dust covering, e.g. growing beside a dirt road, are especially prone to mite infestation. Predatory mites can be an effective means to control spider mites and keep them in check over the season. Releases should only be made when spider mites are present in the field to provide the predators with a source of food. Most of the products labeled for controlling spider mites will also kill predatory mites; so do not use these products after predators have been released. Scout for mites often during the season by examining the undersides of the leaves. Control is warranted if more the 25% of leaves examined have mites.

Two-Spotted Spider Mites
Product Days to Harvest
Brigade® 0
Zeal® 1
Vendex® 1
Acramite® 1
Danitol® 2
Agri-Mek® 2
Oberon® 3
Savey® 3
Kelthane® 3

Potato leafhoppers, sap beetles, thrips and spittlebugs may also become problems on day-neutral strawberries, but are less frequently observed than tarnished plant bug and spider mites. Recommendations for these insects can be found in the current edition of the New England Small Fruit Management Guide.

Gray Mold on Strawberries

Gray Mold on Strawberries, photo by James Dill

Foliar and fruit diseases also need to be managed on day-neutral strawberries, and should be controlled in much the same way as they are for June-bearing varieties. Most of the fungicide products labeled to control gray mold, powdery mildew, leaf spot and leaf scorch have either zero or one day to harvest, so protecting blossoms at the same time as fruit is near harvest should not be a problem; but be sure to check labels carefully and schedule your sprays and harvests accordingly. Anthracnose fruit rot can be especially troublesome for day-neutral strawberries, because it grows well under warm conditions and spreads by splashing water, which is encouraged on plastic mulch. Fungicides registered for control of anthracnose include Cabrio®, Abound®, Pristine® and Switch®, all of which have zero days to harvest restriction.

Important Reminder for Pesticide Users:  Fruit, vegetable or grain growers who use general use (over-the-counter) pesticides and annually sell more than $1,000 of plants or plant products intended for human consumption will be required to have an Agricultural Basic Pesticide Applicator License by April 15, 2015. In the past, only farmers using restricted use pesticides were required to have a pesticide applicators license. The new law extends the licensing requirement to all commercial growers who use pesticides. Training and testing sessions for unlicensed farmers will be held across the state this fall and winter. For more information contact the Pest Management Office at 1.800.287.0279.

Visit the 2014-2015 New England Small Fruit Management Guide online for more detailed pest information.

Sincerely,

David T. Handley
Vegetable & Small Fruit Specialist

Highmoor Farm                       Pest Management
P.O. Box 179                             491 College Avenue
Monmouth, ME  04259         Orono, ME  04473
207.933.2100                           1.800.287.0279

Where brand names are used it is for the reader’s information.  No endorsement is implied nor is any discrimination intended against products with similar ingredients.  Always consult product label for rates, application instructions and safety precautions.  Users of these products assume all associated risks.

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