Addition of ammonium acetate to torula yeast borax and its effect on captures of three species of economically important fruit flies (Diptera: Tephritidae)

Many countries operate continuous trapping programs to detect invasive fruit flies (Diptera: Tephritidae) that threaten fruit and vegetable production. Food-based attractants are an important component of these programs, as they are generalized baits that attract both sexes of all target species. However, food baits are considered weak attractants, and the development of improved food attractants would benefit surveillance efforts. Prior work on protein bait sprays demonstrated that the addition of ammonium acetate increased their attractiveness to tephritid fruit flies, and the present study was conducted to determine whether adding ammonium acetate to torula yeast borax solution (a commonly used food bait) similarly increased its attractiveness. Four field experiments were performed in Hawaii comparing captures of Ceratitis capitata (Wiedemann), Bactrocera dorsalis (Hendel), and Zeugodacus cucurbitae (Coquillett) in Multilure traps baited with standard torula yeast borax solution or with the standard solution plus 1% ammonium acetate. Captures of C. capitata and B. dorsalis were significantly higher for the ammonium acetate-supplemented solution, while results for Z. cucurbitae were inconsistent. In one experiment involving only C. capitata, an additional bait having 5% ammonium acetate was included, and captures for both 1% and 5% ammonium acetate exceeded the standard solution but did not differ from one another. Sex ratios of captured flies were similar between food baits for all three species. These results are compared with similar studies on Anastrepha spp., and implications for surveillance programs are discussed.