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Strawberry IPM Newsletter No. 5 – June 12, 2015

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


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.


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.

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