Apple maggots infest apples, pears, plums, apricots, hawthorns and crabapples according to the Michigan State University Extension. Apple maggots grow into the pupal stage during the winter, turning into flies during the summer. Eggs are deposited inside an apple by the fly puncturing the skin of the fruit. The area sinks and as the maggot eats its way through the fruit, a brown line appears. Apple maggot flies must be killed before it can lay eggs.
Hang bright yellow panels or red balls around the trees in your orchard and cover the material with a brush-on sticky solution such as Tangle-trap with a covering of ammonium acetate, according to Washington State University. Ammonium acetate is available at many pharmacies. The combination of sticky material and ammonium acetate attracts the fly.
Use crochet balls or a 1/4-inch wood panel cut to 5 1/2 by 9 inches for the baiting area. Clear leaves and other debris from the sticky material, according to Washington State. Use 1/4 teaspoon ammonium acetate crystals to 3 tablespoons of the brush-on sticky material.
Lay traps in early July when flies hatch and are ready to lay eggs.
Cover apples using a nylon footy or plastic or paper bags to protect the fruit from the apple maggot fly. Replace paper bags and plastic bags as they wear.
Apply an organo-phosphate pesticide to the apple tree according to the instructions on the pesticide container, if the other measures do not control the apple maggots, according to Washington State. Most organo-phosphate pesticides for public use are removed from the market due to environmental concerns.