Spotted Wing Drosophila Alert: September 29, 2017

Male Spotted Wing Drosophila
Male Spotted Wing Drosophila; photo by Griffin Dill. Actual size: 2-3 mm.

David Handley, Vegetable and Small Fruit Specialist; James Dill, Pest Management Specialist; Frank Drummond, Professor of Insect Ecology/Entomology

Spotted wing drosophila numbers were variable from site to site this week, with some locations seeing little change or a slight decrease from last week, while others showed a significant increase. This may be due to the availability of fruit at each site, as the season starts to wind down, spraying at a site, or trap exposure during the recent hot, sunny days. It is important to note, however, that all locations still have drosophila numbers high enough to cause significant damage to any ripening fruit remaining in the fields. (See table below.) Fall raspberries and day-neutral strawberries are very susceptible at this time. We have also had reports of peaches being infested over the past week. Typically, thicker-skinned fruit like peaches, plums and grapes are not very susceptible to spotted wing drosophila unless the skin is cracked or wounded, which provides the flies with easy access to the flesh for egg laying. It is important to keep wounded and rotten fruit out of the field as much as possible. Allowing it to stay on the plant or on the ground will attract more flies and provide food and shelter for more eggs and larvae.

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

Growers with any ripening fruit should continue protecting their crop against egg-laying drosophila. A minimum spray interval of 5 to 7 days is recommended to keep fruit from becoming infested.

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

David T. Handley
Vegetable and Small Fruit Specialist

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

UMaine Extension Diagnostic Research Lab, Pest Management Unit, 17 Godfrey Drive, Orono, ME 04473, 1.800.287.0279

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Town Spotted Wing Drosophila weekly trap catch 9/15/17 Spotted Wing Drosophila weekly trap catch 9/22/17 Spotted Wing Drosophila weekly trap catch 9/29/17
Wells 330 45 527
Limington 734 373 80
Limerick 1771 174 799
Cape Elizabeth 1308 879 204
New Gloucester 383 341 259
Bowdoinham 792 264 746
Dresden 1584 554 2064
Freeport 132 359 111
Poland Spring 1145 1866 2608
Mechanic Falls 48 113 51
Monmouth 470 63 1624
Wales 86 104 450
Farmington 1848 286 440