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New cherry tree worm #790660

Asked May 13, 2022, 4:35 PM EDT

New cherry has worm

What to do?

Douglas County Oregon

Expert Response


By your description you may have a problem with spotted wing drosophila. SWD turn cherry fruit flesh brown, making the fruit unappealing for both fresh consumption and for processing. The white maggots are easy to see in the red flesh of the cherries, and the maggots will grow even after the fruit is picked. Cherries with maggots decay rapidly.
Management of SWD can be challenging but is best achieved through a combination of detection, sanitation, and insecticides. The best control appears to be when gardeners destroy infested fruit to kill larvae, while using an insecticide to kill the adults at the same time.
Gardeners who are concerned about SWD should monitor for the presence of adults. Take a large clear plastic cup with a cover. Make several holes, 3/16 in diameter, near the top on one side of the cup. Larger holes will allow larger flies and other insects such as sap beetles to enter the trap, making detection of the SWD more difficult. The easiest way to make the holes is to heat a small (8 or 10 penny) nail, which can melt the right size hole in the cup. Pour one to two inches of apple cider vinegar into the bottom of the cup. You can then either add a yellow sticky card slightly above the vinegar or a little bit of liquid soap such as dish soap. Hang traps on branches in a shaded location near fruit. Replace the sticky card and apple cider vinegar bait at least once a week for SWD, disposing of the apple cider vinegar away from the trap location. Checking traps more often can be beneficial for early detection of adult SWD, especially early in the growing season.
Remove and dispose of all infested fruit to keep SWD numbers low. The larvae can be killed by microwaving the fruit, cooking the fruit or placing the fruit in a sealed plastic bag that will be put in the trash. Do not bury infested fruit or place fruit in a compost pile as the adults can still emerge.
Apply insecticides as soon as adults are caught in a trap. Repeat applications will probably be necessary; continue to monitor the trap throughout the growing season. Insecticides should be applied in the evening to avoid killing honeybees and other pollinators. Available insecticides to kill adult SWD are permethrin, carbaryl, malathion, spinosad and pyrethrin. Spinosad and pyrethrin are approved for organic production. Always read and follow labels when spraying pesticides, and follow the pre-harvest interval for all products.
Here are some publications you will find useful.

https://extension.oregonstate.edu/pests-diseases/insects/how-make-trap-catch-spotted-wing-drosophila-fly

http://msue.anr.msu.edu/news/potential_for_spotted_wing_drosophila_infestation_in_dropped_cherries

Hope this helps!!

chris Rusch Replied May 14, 2022, 12:13 AM EDT

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