Experiments were conducted in 2005 and 2006 in western Washington state to determine effects of adding ammonium carbonate (AC) and ammonium acetate (AA) to GF-120 NF Naturalyte® Fruit Fly Bait (Dow AgroSciences, Indianapolis, IN) on attraction, feeding, and control of the apple maggot fly, Rhagoletis pomonella (Walsh). In the field, sticky yellow panel traps baited with GF-120 10% AC attracted more flies than those baited with GF-120 10% AA or GF-120 alone. In the laboratory, female flies responded more frequently to sucrose and 20% GF-120 than to water and 40% GF-120 10% AA on apples, perhaps because of the confined conditions during testing. In the field, fly attraction and feeding were greater for GF-120 10% or 2.5% AC or AA than GF-120 alone on apple leaves. In 2 spray tests with 100 mL of GF-120 alone and GF-120 2.5% AC or AA applied on single apple trees, larval infestations in fruit were reduced up to 99% compared with controls, but there were no differences among treatments, and none was different from spinosad alone. Results indicate the attractiveness of GF-120 to R. pomonella can be increased with added ammonia, but that this does not necessarily result in greater control, perhaps because the added ammonia volatilizes too quickly. Results suggest that at the spray volumes used, GF-120 alone or even spinosad alone can greatly reduce local R. pomonella populations in Washington.