Behavioural and Electrophysiological Response of Anastrepha fraterculus (Diptera: Tephritidae) to a γ-Lactone Synthetic Semiochemical

SIMPLE SUMMARY: Specific attractants are one of the best allies in insect-integrated pest management. At present, monitoring of Anastrepha fraterculus, a species of great economic importance in South America, relies on food-based attractants with poor selectivity and high cost, from an operational perspective. Here, we analyzed the response of A. fraterculus to different semiochemicals recently synthesized. This response was conditioned by the physiological condition and sex of the flies. To our knowledge, this is the first report that clearly shows a sexual role of epianastrephin in A. fraterculus. A structurally related, naturally occurring γ-lactone, (±)-trans-tetrahydroactinidiolide, gave a promising performance since flies responded to it as they did to epianastrephin; however, it has an advantage over epianastrephin since it is easier to synthesize and could serve as an effective early-detection attractant, particularly in pest-free areas such as entry ports in importing countries. Variations of attraction according to flies’ physiological status and age are also an important finding for pest management since they contribute to improving the available attractants and trapping effectiveness of A. fraterculus. We suggest that open field evaluations in commercial orchards will ultimately determine the possibilities of implementing these semiochemicals as new attractants for A. fraterculus. ABSTRACT: Attractants are a powerful tool for pest management. The lack of specific attractants for the South American fruit fly, Anastrepha fraterculus, a complex of cryptic species of great economic importance in South America, makes it difficult to monitor the pest in the field. The γ-lactone male sex and aggregation pheromones of several Anastrepha species, naturally released in a 7:3 epianastrephin to anastrephin ratio, and a structurally related naturally occurring γ-lactone ((±)-trans-tetrahydroactinidiolide) with gem-dimethyl groups (dimethyl) at C(4), were evaluated as potential attractants of this species. Different age and mating conditions of A. fraterculus males and females were evaluated during electroantennography (EAG) and field cage experiments in which polymeric lures were deployed to contain 100 mg of attractant. Epianastrephin and dimethyl were EAG+ for all fly conditions, with epianastrephin eliciting the highest response for both sexes and immature flies showing greater responsiveness than mature flies. In the field cage experiments, immature flies were only attracted to leks; virgin females were attracted to leks, dimethyl, and both epianastrephin-anastrephin formulations (95 and 70 wt.% epianastrephin); mature-mated males were attracted to leks, dimethyl and 70 wt.% epianastrephin; and mature-mated females were only attracted to leks. Our bioassays showed a promising performance of the analog dimethyl since it elicited the same response as epianastrephin, requires fewer steps to synthesize, and contains one less chiral center than the natural pheromones. The attraction to leks was recorded for all mating conditions and ages of flies and suggests that air-borne volatiles of calling males contain cues that could act as sensory traps. The addition of any of these compounds in the synthetic attractants may result in a greater attraction and thus deserves further evaluation. Dose-response experiments will provide additional information to move a step forward and validate the results obtained in open-field conditions.