Technical Abstract: Baits formulated from attractants, phagostimulants, adjuvants and conditioners were tested in field cages, orchards with sterile flies, and in laboratory cages with fertile flies. The formulation tested was based on the commercial fruit fly bait, GS-120, containing spinosad and manufactured by Dow AgroSciences. This bait was developed with spinosad concentrations that require ingestion for mortality to limit toxicity to non-target insects. The formulation contains additives that are repellent to bees and parasitic Hymenoptera. Our interest in testing the sprays was to examine the effects of dilution and aging on attraction and fly killing qualities of the bait when applied as spot sprays. Dilution and age effects on the bait are important both as a factor in bait costs, application frequency, and equipment requirements for application. Our results indicated that in most tests the spinosad maintained toxicity for up to 3 weeks, the concentration of spinosad in the recommended formulation of the bait (80 ppm = 80 mg/liter) killed fewer flies when measured over short time periods than higher concentrations (200 ppm), but numbers of survivors 4 days after treatment was similar for the two concentrations. When the GF-120 bait was modified by omission of the preservative Proxel, there was no loss of effectiveness of the bait in either the recommended or diluted concentration, or in fresh or 10 day old bait. This indicated that the microbial breakdown of the bait is not a factor in aging and that the bait modifications required for organic registration did not diminish bait function.