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Western Cherry Fruit Fly

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Larry Sagers Horticultural Specialist Utah State University Extension Service Thanksgiving Point Office © All Rights Reserved


The first emergence of western cherry fruit fly adults have been detected in warmer areas of northern Utah (primarily Box Elder, Davis and Utah Counties). The first catch of fruit flies in the traps used to monitor their development indicates it’s time to protect developing sweet and tart cherry fruits from infestation with tiny white worms.

According to Diane Alston, Utah State University Extension entomologist these are some things you should know to help keep the worms away from your cherries.

The western cherry fruit fly is small with dark bands on its wings. It over winters in soil under cherry trees and adults emerge the following spring from late May to early June in northern Utah.

Once the fruits take on a salmon to rosy blush in color they become soft enough for female fruit flies to penetrate the skin to lay eggs. After the eggs develop under the skin, they hatch into white worms that feed on the flesh of fruits.

Insecticides are the primary control for cherry fruit fly. It is most effective if all cherry trees in an area are treated to prevent flies from emigrating from infested sites. Let your neighbors know and encourage them to spray to help keep the fruit fly populations down.

Effective insecticides for the homeowner include permethrin, phosmet (Imidan; not for use on sweet cherries), diazinon (if your package lists cherries as a registered use), carbaryl (Sevin), methoxychlor, malathion, pyrethrum (Pyganic), endosulfan (Thiodan), and spinosad (Success or Entrust).

Organic Gardeners can use a pyrethrum/ rotenone mix. Also consider using small nylon netting purchased from rabbi stores to keep the flies and the birds out of your plants.

A cultural control method is placing plastic landscape fabric or another barrier under the canopy of cherry trees to prevent larvae in dropped fruit from burrowing into the soil where they will pupate for the winter.

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