Insights into the Functional Responses of Four Neotropical-Native Parasitoids to Enhance Their Role as Biocontrol Agents Against Anastrepha fraterculus Pest Populations.

Abstract

Anastrepha fraterculus (Wiedemann) (Diptera: Tephritidae) is a significant fruit pest of economic and quarantine importance in South America. Biological control using augmentative releases of parasitoids or conservation strategies for these natural enemies are handy tools in integrated fruit fly management programs. The functional response describes the natural enemy consumption rate with increasing resource density. Such information may be relevant for selecting the parasitoid species that is potentially most suitable to serve as a biocontrol agent of A. fraterculus. Furthermore, the number of discarded hosts determined from functional response analysis might be used to estimate suitable host densities, avoiding wastage of larvae/puparia associated with host overproduction. Therefore, the current study aimed to evaluate the functional response of four Neotropical-native parasitoid species commonly associated with species of the Anastrepha genus in the Americas, such as the pupal parasitoid Coptera haywardi (Ogloblin) (Hymenoptera: Diapriidae) and the larval parasitoids Ganaspis pelleranoi (Brèthes) (Hymenoptera: Figitidae), Doryctobracon crawfordi (Viereck), and Opius bellus Gahan (Hymenoptera: Braconidae). The package "frair" from R software was used to determine the functional response type and parameter estimation, enabling selection, fitting, and comparison among standard functional response models and integral parameters. Four relevant conclusions can be highlighted: (a) G. pelleranoi showed a flexible functional response, with a statistically significant deviation to a Type III rather than a Type II response found among the three other parasitoid species; (b) G. pelleranoi had a handling time significantly lower than the other tested parasitoid species; (c) the number of attacked hosts varied among all four parasitoid species, with C. haywardi and G. pelleranoi exhibiting the highest proportion of attacks at low and high host densities, respectively; and (d) the percentage of discarded hosts was significantly low at 1-5 and 1-20 hosts per parasitoid in C. haywardi and G. pelleranoi, respectively, whereas in both D. crawfordi and O. bellus, it was high at any offered host density. Results provide helpful comparative information about the possible performance of these species as biocontrol agents against A. fraterculus populations within augmentative and/or conservative biological control programs.