JoAnne Skelly: Avoid wormy apples, take precautions

Apples picked fresh off the tree taste so delicious, until you look at your half-eaten apple and find a worm or the brown mess left by a worm. If you had apples with worms last year, it is likely you will have wormy apples this year too, unless you take precautions.

Worms in apples are the caterpillar larvae of codling moths. These relatives of butterflies also attack pears, plums and walnuts. Each female moth lays 30 to 70 tiny disc-shaped eggs singly on the fruit, spurs or nearby leaves. After hatching, the white to light-pink “worms” with dark heads bore into the fruit. Later, the caterpillars leave the fruit and look for sites for pupate overwinter before becoming adults in the spring. Moths are active only a few hours before and after sunset, and they mate when sunset temperatures exceed 62 degrees. There are usually two generations per year.

Control of codling moth starts with good sanitation. Cocoons (pupae) overwinter in protected areas under the bark on trunks, in debris under the trees or in soil. To reduce new populations, remove the loose bark on the trunk and any cocoons you find, along with any fallen apples or leaf litter from last year. Be sure not to compost any of these materials. From late spring through harvest, pick up fallen apples daily to reduce reproduction.

Another method to manage these annoying pests is to select varieties less susceptible to damage, such as early maturing apples and pears. A labor-intensive way to keep the worms out of fruit is to bag as many individual fruits as you want to eat. Do this when the fruit are half-an-inch to one-inch in size. Thin the fruit to one per cluster. Then cover with a standard lunch bag and seal it. The apple will grow inside. Red apples will be a light color from being hidden in a bag away out of the sun.

Timing the application of insecticides for codling moth control is difficult. Products must be applied just as the eggs are hatching, but before the caterpillars go into the fruit.

For more detailed information, see the source for this article from University of California at Davis:

Attend tonight’s lecture, “Weed’s, Critters and Insects,” from 6 to 8 p.m., or Thursday’s “Growing Garlic” class. Both will be held at 2621 Northgate, Suite 12, Carson City. The fee is $5 per class. Exact change is required.

JoAnne Skelly is the Carson City/Storey County Extension educator for University of Nevada Cooperative Extension and may be reached at or 887-2252.


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