Various species of fruit flies and their larvae can damage fruit. A few common pests that affect apples, blueberries, cherries, pears and plums are described below. Apple maggots (alternately, apple fruit flies or railroad worms) hatch from the eggs of a fly slightly smaller than the common housefly. The adult is black with yellow legs, a yellow-striped abdomen, and zigzag bands across the wings. It lays its eggs singly in the skin of apples, blueberries, cherries, pears and plums. The emerging maggot is white or yellowish and about 1/4 inch long. Unfortunately, their presence is very hard to detect until the damaged fruit is bitten into or otherwise opened. They are particularly troublesome after a cold spring. Cherry fruit flies resemble small houseflies with barred wings. The maggots are yellowish white and legless with 2 dark mouth hooks. They leave the fruit of cherry, pear and peach trees small and misshapen; sometimes cherries will drop prematurely. In addition, the maggots may be found feeding in rotten flesh.
The best way to prevent damage from either of these pests is to control adults before eggs are laid. Use commercially available red spherical sticky traps, ideally hung 4 to 5 per tree, to monitor their arrival. To avoid harming beneficial insects, remove traps after 3 or 4 weeks. Kill overwintering insects by cultivating the top 2 inches of soil under fruit trees very late in the fall to expose them to cold and to predators.