The most destructive pest of apples in our area is the apple maggot or "railroad" worm. The adult lays eggs just underneath the skin of the immature fruit. The apple maggot larvae mines in the flesh leaving irregular and winding brown tunnels, which often cause premature dropping of the fruit. Wormy fruits have very little value for either eating or cooking.

The adult is a fly, a little more than a 1/4 inch long and dark brown in color. The adults begin emerging from the soil in June, continuing for a month or more. Within a week or two after emergence, they lay eggs in the fruits. Hatching occurs within a few days and the larvae starts feeding in the apple. They feed from two weeks in early maturing fruits to longer periods in later apples. When fully developed, the maggots drop out of the fruit, crawl into the soil and continues its life cycle.

Good sanitation and prompt destruction of dropped fruits are important in controlling the insects. Fallen apples should be picked up twice a week from early July through August to prevent the maggots from burrowing out of the apple into the soil. A spray program should be initiated each year at the time of fly emergence (mid to late June) and continued every 7-10 days through mid-August. Once the egg has been laid into the fruit, spraying with an insecticide won't control the developing worm.

Diazinon and Sevin are two insecticides recommended for apple maggot control. Sevin is available in either the liquid or wettable powder form. If your apple tree has a good fruit set, seriously consider apple maggot control.

This page was last updated April 2003

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