Visual cue and chemical cue interactions in a dry trap with food-based synthetic attractant for Ceratitis capitata and Anastrepha ludens (Diptera: Tephritidae)

Several modifications of a plastic dry trap baited with synthetic lures (ammonium acetate and putrescine) were field tested in Guatemala for capture of the Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and the Mexican fruit fly, Anastrepha ludens (Loew). The cylindrical plastic dry trap has 3 holes for release of internally placed chemical lure as well as for insect access into the trap, and a painted band that provides a visual cue. Fruit flies entering the trap move to internally placed toxicant-sugar panels, causing insect death after they feed. Visual cue modifications in traps painted green or orange included comparisons between shiny or dull trap exteriors and among a range of widths of the painted band on the trap body (3-15 cm wide). Chemical cue modifications included 3 versus 6 access holes in the body of the cylindrical dry trap and tests of 2 doses of a new putrescine formulation. The greatest amount of discrimination among the tested modifications was demonstrated by female C. capitata, The highest capture of female C, capitata was in green 3-hole traps with dull exteriors and with visual cues 12-15 cm wide. Variation in the width of the visual cue and in the number of access holes had less effect on capture of male C. capitata than on females, but capture of males was the lowest in orange traps with shiny exteriors. Capture of female A. ludens was relatively unaffected by the modifications tested, although highest capture was obtained with the green visual cue of 3-7.5 cm and the orange visual cue of 7.5-12 cm. Male A. ludens response was similar to that observed in females, although the capture of males among the modifications tested was more variable. There were interactions between visual cues associated with the trap body and the dose of putrescine, thus optimal dose of putrescine may vary with visual cue used in the trap design. Results from this study indicate that modifications in the plastic dry trap can be used to improve the capture of female C. capitata and to develop more cost-effective dry traps for field use against pest Tephritidae.