Field survey of Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) in Maui, Hawaii

Drosophila suzukii (Matsumura) and Zaprionus indianus Gupta (Diptera: Drosophilidae) are notable agricultural pests of soft-skinned fruits. Efficient field surveying is vital in an integrated pest management program. A survey to identify D. suzukii populations was conducted in four localities in Maui County among seven host-plants. During the survey, adult Z. indianus specimens were collected at all four localities in traps positioned in six of the seven host plants, suggesting that this previously unreported exotic species may already be well-established. Though there are currently no species-specific attractants available for D. suzukii or Z. indianus, characterization of attractant specificity by species and understanding how attractant efficacy varies with time is needed to advance development. A modification of the deli-cup trap was used and five attractants (brown rice vinegar, apple cider vinegar, red wine, brown rice vinegar plus red wine, apple cider vinegar plus red wine) were deployed in cherimoya in Kula, Maui, Hawaii. This investigation includes the first reported use of brown rice vinegar as an olfactory attractant in the United States and the results suggest that it may have higher specificity in the field capture of D. suzukii than apple cider vinegar, red wine, and apple cider vinegar with red wine. No significant differences were observed in attractant specificity for the field capture of Z. indianus. To examine attractant efficacy over time with and without a preservative, traps were maintained daily in cherimoya. The results suggest that attractants up to seven days old had a significant effect on mean field captures of D. suzukii and non-target drosophilids. Inclusive of all attractants and field ages, The addition of 1% boric acid (w/v) to the attractant solution increased the total field captures of D. suzukii by 44%, but no effect was observed for non-target drosophilids. These investigations enhance our current understanding of attractant specificity, which is the first step towards identifying selective compounds for a species-specific attractant. Furthermore, the first report of Z. indianus in Hawaii highlights the importance of examining interspecies interactions between endemic and invasive drosophilids and the need for the establishment of economic thresholds for vinegar fly pests.