My everbearing raspberries have been infested with tiny worms the last 3...

Asked October 21, 2014, 10:44 AM EDT

My everbearing raspberries have been infested with tiny worms the last 3 seasons. Last year they seemed to disappear once the weather got cooler at night. However, this year it did not seem to make any difference. I lost a lot of beautiful raspberries. Is there any type of product I could use this fall to spray the ground to kill any eggs or larva that is present. Also, is there anything I can do next year to try to control this situation? I don't want to spray after the raspberries have formed on the plant. Any help you can give me would be appreciated.

Kandiyohi County Minnesota

3 Responses

The tiny worms may be the maggots of the Spotted Wing Drosophila (SWD), Drosophila suzukii. The tiny, white cylindrical maggots are a little longer than 1/8 inch when full grown. The Spotted wing drosophila is a fruit fly that often attacks undamaged fruit. Remove overripe, old, diseased, or missed fruit and maintain a high level of sanitation in the field to reduce SWD breeding sites. Infested fruit should be placed in a plastic bag, sealed, and placed in the trash. Composting or burying is not a reliable way to destroy eggs and larvae in fruit. Fine netting over whole plants or canes can be useful to keep flies from attacking fruit on small fruit. The netting must be applied before fruit begins to ripen so that flies will not be caught inside the net. Netting must be secured so flies cannot enter, and the mesh size should be very small, such as 0.98 mm mesh used for screening out no-see-um flies.

The netting is a good suggestion. However, that would prevent any bees from continuing to pollinate new blossoms on my everbearing raspberries. I have always tried to clean up all debris in the fall after cutting down the canes to the ground and disosed of it in the trash. I also try to keep berries picked so there are not overripe fruits. The worms are found in berries that are at their prime or even some underripe, firm berries.

Most Drosophila species attack split, rotting or fermenting fruit. Spotted wing drosophila, however, readily attacks undamaged fruit.

Raspberry flowers are self pollinating but bee activity is still responsible for 90-95% of pollination.