Spotted Wing Drosophila Alert: August 6, 2018

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

Spotted Wing Drosophila Larvae in Blueberry
Spotted Wing Drosophila Larvae in Blueberry; photo by David Handley. Click on photo to enlarge.

Captures of spotted wing drosophila (SWD) fruit flies in vinegar/yeast traps in raspberry and highbush blueberry plantings remained low in most locations, although at two sites ((Limington, Readfield) counts rose above threshold levels. (See table below.) The recent warm, wet weather will encourage SWD infestations, however, as it may lead to more rotten fruit in the field and increase ambient moisture levels. Growers should try to keep rotten fruit out of the field as much as possible and encourage dry conditions by pruning out excess growth, especially near the base of the plantings. Growers who have been catching flies in their traps for more than one week and have ripening fruit should put on a protectant spray.

We expect spotted wing drosophila populations to increase significantly in the coming weeks as more ripe and rotten fruit becomes available for the flies. Protective sprays should be applied if more than four spotted wing drosophila flies are caught in a trap, flies are caught consistently for more than one week, or any larvae are noticed in the fruit. Look for fruit flies hovering around fruit and symptoms of premature fruit decay.

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

Other IPM Web Pages

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 7/20/18 Spotted Wing Drosophila weekly trap catch 7/27/18 Spotted Wing Drosophila weekly trap catch 8/3/18
Wells 0
Sanford 13 3 0
Limington 1 1 12
Limerick 0 0 0
Buxton 3 5 0
Bowdoinham 1 1 2
Cape Elizabeth 1
Dresden 5 2 5
Freeport 0 0 0
Poland Spring 1 0 0
Mechanic Falls 0 0 0
Monmouth 3 0 2
Readfield 0 1 12
Wales 5 2
Farmington 8 1
Fayette 0 0 0
Wayne 0 0