The apple maggot, Rhagoletis pomonella (Walsh), is a serious pest of apples in the United States, requiring reliable monitoring and control programs. Various synthetic apple volatile lures with and without protein hydrolysate, ammonium acetate, or ammonium carbonate were evaluated from 1998-2000 for their attractiveness to R. pomonella adults with red sticky-sphere (9 cm diam.) monitoring traps. A blend consisting of butyl butanoate (10%), propyl hexano- ate (4%), butyl hexanoate (37%), hexyl butanoate (44%), and pentyl hexanoate (5%) was the most effective lure tested for attracting both sexes of R. pomonella adults during all three field seasons. The addition of protein hydrolysate or ammonium compounds to spheres baited with a commercial attractant (BioLure) consisting of plastic dispensers containing butyl hexanoate, did not significantly increase apple maggot fly captures. Spheres baited with the blend or with butyl hexanoate in polyethylene vials and spheres baited with BioLure dispensers were highly selective in capturing R. pomonella flies relative to non-target insects. However, spheres baited with ammonium compounds with or without synthetic apple lures were non-selective with respect to apple maggot captures. Protein hydrolysate alone was ineffective for monitoring R. pomonella flies. We provide further evidence that baiting red-sticky sphere traps with the volatile blend without ammonium bait additives creates a highly effective and selective device for capturing apple maggot flies. The blend could be an important addition to current monitoring and control programs for apple maggot flies in Michigan orchards and other important apple growing regions
