Spotted Wing Drosophila and Berry Notes — October 4, 2024
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
Spotted Wing Drosophila:
Fly counts in our vinegar/yeast traps this week were very similar to last week (see table below). For growers still harvesting late ripening fruit, we recommend continuing regular protective sprays to protect against SWD infestation. The presence of any larvae in ripening fruit should also initiate a regular spray program if you are not using traps to monitor the flies. This week, fruit fly counts ranged from 9 to 841 in our traps, indicating that ripening fruit in most locations still require regular protection to prevent infestation. A 5- to 7-day spray interval should minimize fruit infestation, depending on the level of pest pressure in a given field.
For more information on identifying spotted wing drosophila (SWD) and updates on populations around the state, visit our SWD blog.
Berry Notes:
I have been seeing a lot of highbush blueberry bushes infested with galls caused by the blueberry stem gall wasp. The galls appear on this year’s shoot growth, usually near the tip. They are usually about an inch long and kidney-shaped. These growths can reduce the number of fruit buds formed on the new shoot in the fall when the infestation is heavy. Blueberry varieties vary in susceptibility; Jersey is very susceptible, while Bluecrop is practically immune. The galls contain the larvae and pupae of the next generation of wasps which will emerge next spring about when the plants are in flower. Pruning out the galls in the winter can help reduce the problem, but only if it is done before the wasps emerge and the galls are destroyed, either by burning or deep burial. Insecticide sprays just post bloom can reduce the damage. Do not spray insecticides during bloom when pollinators are active. To learn more about gall wasp, see this blueberry stem gall wasp fact sheet.
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- Close up of gall on blueberry stem; photo by David Handley, UMaine Cooperative Extension
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- Blueberry bush showing several galls; photo by David Handley, UMaine Cooperative Extension
Late Leaf rust has been showing up on fall raspberries over the last two weeks. This is a fungus disease which appears as faint yellow mottling on the upper side of the foliage, and yellow-orange dust-like spores on the underside of the leaves. The spores may also develop on the fruit making it unmarketable. Keeping good air circulation through the planting by proper pruning and trellising, and keeping weeds down in the planting can help reduce the incidence of rust. Several fungicides are also effective against this disease. See the New England Small Fruit Management Guide for more information. There is a late leaf rust fact sheet for more information.
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- Underside of raspberry leaf showing dust like spores caused by late leaf rust; photo by David Handley, UMaine Cooperative Extension
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- Yellow mottling cause by late leaf rust on raspberry foliage; photo by David Handley, UMaine Cooperative Extension.
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
| Town | SWD weekly trap catch 9/6/24 | SWD weekly trap catch 9/13/24 | SWD weekly trap catch 9/20/24 | SWD weekly trap catch 9/27/24 | SWD weekly trap catch 10/4/24 |
|---|---|---|---|---|---|
| Wells | 2,160 | 988 | 1,504 | 1,023 | 841 |
| Limington | 154 | 12 | 6 | 11 | 9 |
| Bowdoinham | 235 | 204 | 109 | 370 | 180 |
| Mechanic Falls | 674 | 23 | 1 | 63 | 58 |
| Monmouth | 95 | 22 | 60 | 252 | 162 |
David T. Handley
Vegetable and Small Fruit Specialist
Highmoor Farm
P.O. Box 179
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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