Washington State University Extension

Garden Tips

Spray Fruit Trees Now To Keep Worm Free

GARDEN TIPS – written by
Marianne C. Ophardt
WSU Extension Faculty
for the Tri-City Herald, Kennewick, WA Written May 7, 2015

This spring, temperatures have gone back and forth between warmer-than-normal and cooler-than-normal. Because of an early start to the growing season and the cumulative warm weather, our plants and their pests are a bit ahead of schedule.

Two insects that have already emerged are the western cherry fruit fly (WCFF) that attacks cherries and the codling moth (CM) that attacks apples, crabapples, and pears. If you have a cherry, apple, pear, crabapple, flowering pear, or a fruit-producing flowering cherry, you should have already applied an insecticide recommended for control of these pests. If you have not started a regular spray schedule, start as soon as you there is calm weather!

Even if you do not care about harvesting the fruit or if the tree is an ornamental tree susceptible to these pests, you are required by law in Benton, Franklin, Walla Walla, and Yakima counties to control them. The reason for the law is because infested backyard fruit trees can serve as a source of infestation for nearby commercial orchards, causing the orchardists to apply more pesticides or risk having their fruit being rejected due to wormy fruit.

I cringe when I see fruit trees, particularly cherries, apples, and pears, offered for sale at local big box stores and nurseries. Would-be or novice backyard fruit growers are often unaware of the extra work fruit trees require, including regular pesticide applications to control insects, like WCFF and CM, and diseases.

There are some organic insecticides available for control of WCFF or CM, but there are practically no non-chemical strategies. However, homeowners can make it easier to apply sprays by planting dwarf trees and then pruning them to keep the trees at a more manageable height of 10 to 12 feet. Keeping trees at this height will also make it easier to harvest fruit. However, annual pruning means even more work for backyard fruit growers.

GARDEN NOTE: Do not assume a “dwarf” tree will stay small without pruning. Dwarf is a relative term. Fruit trees labeled as “dwarf” may still grow to a considerable size. Check the label for the potential mature height of the tree. A “dwarf” or “semi-dwarf” apple could still reach a height of 15 to 20 feet or more.

Earlier I mentioned that home gardeners are required to keep fruit bearing ornamental crabapple, flowering pear, and flowering cherry trees free of WCFF and CM. Codling moth will even attack the small fruit of flowering pears and crabapples so regular spraying is required to keep these trees “worm-free.”

Japanese flowering cherry trees do not produce fruit, but they are grafted onto a rootstock that will produce fruit if allowed to grow. If these trees are allowed to produce fruit, you are required to keep them worm-free or you might want to remove them because they have lost the beautiful flowers and form of the Japanese flower cherries originally planted.

If you must grow fruit trees consider planting plums, apricots, or peaches which generally do not require regular pesticide applications to keep their fruit free of worms. However, these fruit trees are prone to a number of fungus diseases which will require spraying and again more work to keep the trees healthy and the fruit blemish free.

If you are growing any type of fruit tree and need to know what sprays are needed and when they should be applied, contact the WSU Extension office at 735-3551 for a Home Orchard Pest Management Chart. You can find more information about WCFF at  and CM at

Garden Tips, WSU Extension, Benton County, 5600-E West Canal Drive, Kennewick, WA 99336-1387, 509-735-3551, Contact Us

WSU Extension, Franklin County, 1016 North 4th Ave, Pasco, WA 99301-3706, 509-545-3511, Contact Us
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