The apple maggot (AM), a native of eastern North America, originally bred in large fruited hawthorns (Crataegus sp.). Later, it adopted apple as another host, and it has become a major fruit pest in the northeastern United States and Canada. During the early 1980s, the AM became established in California, Oregon, Washington, Idaho, Utah, and Colorado, although it has not yet become a serious pest in the major apple production areas in these western states. Thorough control is necessary because marketed apples must be free from all AM injury.