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Apple maggot larvae — or "railroad worms" — tunnel into fruit, especially on thin-skinned or early-maturing cultivars.
Adults are dark-colored flies, 1/4 inch (6 mm) long, with yellow legs and transparent wings patterned with dark, crosswise bands. Larvae are white maggots that develop inside fruit.
Eastern United States and Canada; Northern California.
Apple, crab apple, blueberry, occasionally cherry and plum.
Maggots bore through fruit, leaving brown, winding tunnels in the flesh, usually causing fruit to drop early.
Adults emerge from overwintering pupae in the soil from mid-June to July. Female flies lay eggs in punctures in the skin of the fruit; eggs hatch in 5-7 days. The larvae tunnel inside the fruit until it drops. They leave the fruit after completing their development to pupate several inches deep in the nearby soil. One generation per year in most areas; in Southern regions, there may be a partial second generation, with adults emerging in early fall. Some pupae can stay dormant in the soil for several years.
Plant late-ripening cultavars. Collect and destroy dropped fruit daily until September,t hen twice a month in fall. Plant clover groundcovers to attract ground beetles that prey on pupae.
Hang sticky red apple-maggot traps in trees from mid-June until harvest (use one trap per dwarf tree, up to six traps per full-sized tree).