Strawberry IPM Newsletter No. 6 — June 13, 2025

STRAWBERRY HARVEST STARTS IN SOUTHERN MAINE

Be On the Lookout for Fruit Rots, Sap Beetles and Spotted Wing Drosophila

Situation:

Strawberry harvest is getting started in southern Maine, although the picking is light and mostly for stand sales at this point. A few warm sunny days are needed to push the ripening along and get the pick your own season underway. Tarnished plant bugs are still a threat to later ripening fruit still in the bloom to early fruit development phase, but birds and sap beetles may be the greatest threat to ripe fruit.

Tarnished plant bugs: Nymphs are active in strawberry fields, and should be controlled if they exceed the threshold of four or more flower clusters infested per 30 sampled, if there is still any bloom remaining in the field. Populations are spotty from one location to another, so scout your fields for their presence before applying an insecticide.

Sap beetles may become a problem as fruit start to ripen. The 1/8 inch long, dark brown beetles chew small holes in ripening fruit, similar to slug injury. The damage often allows rot organisms, such as Botrytis, to then infect the fruit. 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.

Potatoe Leafhoppers: Reports of damage from this insect have been coming in this week. 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 and may look like herbicide damage. 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 Assail®, malathion, carbaryl or Provado®.

Spotted Wing Drosophila was a major problem in some strawberry fields last spring. Typically, this pest does not build up to damaging numbers until late in the summer, but last year it began infesting some fields midway through the season. Fruit became soft, had no shelf life, and larvae could be found within the flesh. The early arrival last year was likely due to a mild winter, warm temperatures and storms from the south, but be on the lookout for this problem throughout the harvest season. If found, management of this pest can be achieved through sanitation and pesticide applications. For updates, visit our Spotted Wing Drosophila Alerts webpage.

Botrytis gray mold is still a concern for fields still in bloom due to continued wet weather. Likewise, be alert for signs of Anthracnose fruit rot and leather rot as the harvest season begins. Additional fungicide sprays may be needed if weather conditions occur that would stimulate infection. Be sure to use the best product for the particular disease problem found.

Birds, especially cedar waxwings, are moving into fields to feed on ripe fruit. Only by keeping a near constant presence in the field and eliminating roosting sites can you reduce the damage. Avian Control, a chemical repellent containing methyl anthranilate is registered for use on strawberries. Some growers have found this to be helpful, others have seen little effect. Use the higher rate on strawberries and begin applications before the birds are regularly feeding in the field. Songbirds, including cedar waxwings are protected by law and should not be killed.

Bird Damage Prevention for Northern New England Fruit Growers is a free online publication offered by the University of New Hampshire Extension.

Review: Keeping Strawberries Fresh for Market

If you’re bringing fruit to market, make sure that it arrives in the best condition possible. Strawberries cool most efficiently if harvested early in the morning before they build up field heat. Place fruit into refrigerated storage quickly and keep it out of direct sunlight. Fruit should be stored at 32º 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. Temperatures lower than 32º 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.

Annual Pre-Harvest Checklist for Pick-Your-Own

It’s that time again! As harvest approaches, we like to remind you to take a moment and make sure that your farm is prepared to give your customers an enjoyable experience. Take our annual review below to evaluate your customer readiness.

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 & Small Fruit Specialist

Highmoor Farm
P.O. Box 179
52 U.S. Route 202
Monmouth, ME 04259
207.933.2100

UMaine Cooperative Extension Diagnostic and Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473
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 labels for rates, application instructions and safety precautions. Users of these products assume all associated risks.

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The University of Maine System is an equal opportunity institution committed to nondiscrimination.