Spotted Wing Drosophila Alert and Berry Notes — August 11, 2023

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist, Phil Fanning, Assistant Professor of Agricultural Entomology, Christina Howard, Maine New Farmer Project Manager

SWD Maggot in Raspberry
SWD Maggot in Raspberry; photo by David Handley

Spotted Wing Drosophila:
Numbers of spotted wing drosophila fruit flies caught in our traps have risen at all locations this week, and larvae have been observed in fruit at several sites. At all sites numbers are high enough to be over control thresholds, so regular sprays are now recommended to protect ripening fruit. Good coverage has been difficult with the frequent heavy rain events we’ve experienced. If significant rain falls after an application and before the product has had a chance to dry, it will likely be washed off and its effectiveness reduced. If the spray has dried, but the field receives more than an inch of rain after the application, it is likely that much of the product has washed off and its effectiveness greatly reduced. In these situations, growers should consider putting on another application to ensure effective protection.

At this point, a 5-7 day schedule of sprays may be needed to minimize fruit infestation in fields.

For more information on identifying spotted wing drosophila (SWD) and updates on populations around the state, visit our SWD blog.

Gray Mold on Strawberries
Gray Mold on Strawberries; photo by James Dill

Berry Notes:

  • All the rain has greatly increased the incidence of fruit rots for all summer berry crops, most notably gray mold (Botrytis) and anthracnose. Growers should apply appropriate fungicides either before a predicted rain, if there is time for the product to dry, or as soon as possible after a rain, using a product that has some “kickback”, and can stop an infection that has already started. More information on fungicides is available in the New England Small Fruit Guide.

Other IPM Web Pages
Michigan State University Spotted Wing Drosophila
Penn State University Spotted Wing Drosophila Overview
University of New Hampshire SWD Weekly IPM Reports

David T. Handley
Vegetable and Small Fruit Specialist

Highmoor Farm
P.O. Box 179
Monmouth, ME 04259

UMaine Extension Diagnostic Research Lab
Pest Management Unit
17 Godfrey Drive
Orono, ME 04473

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.

The University of Maine is an equal opportunity/affirmative action institution.

Weekly Spotted Wing Drosophila Trap Captures

Town Spotted Wing Drosophila weekly trap catch 7/21/23 Spotted Wing Drosophila weekly trap catch 7/28/23 Spotted Wing Drosophila weekly trap catch 8/4/23 Spotted Wing Drosophila weekly trap catch 8/11/23
Wells 7 8 22 166
Sanford 7 5 3 106
Limington 3 1 2 19
New Gloucester 120 1190 214 280
Mechanic Falls 0 1 20 34
Bowdoinham 15 85 42 138
Monmouth (unsprayed plot) 1 13 43 114
Fayette 5 23 103
Wayne 8