Sublethal effects in pest management: a surrogate species perspective on fruit fly control

Authors: BANKS, JOHN - University Of Washington; Vargas, Roger; ACKLEH, AZMY - University Of Louisiana At Lafayette; STARK, JOHN - Washington State University

Submitted to: Insects
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2017
Publication Date: 7/29/2017
Citation: Banks, J.E., Vargas, R.I., Ackleh, A.S., Stark, J.D. 2017. Sublethal effects in pest management: a surrogate species perspective on fruit fly control. Insects. 8(3):78.

Interpretive Summary: Understanding the mechanisms underlying population dynamics governing economically important pest species is of prime importance in the development and maintenance of integrated pest management schemes that often incorporate pesticides. A common method of anticipating the effects of a toxicant on target and non-target organisms is to test the effects on one species and extrapolate to a wider range of closely-related species. This so-called “surrogate species” approach is used widely in conservation science, and also has applications in biological control, especially for the protection of natural enemies. We use a simple mathematical model here to explore the utility of such a surrogate species approach in assessing the efficacy of pesticides in controlling three economically important fruit fly species, oriental fruit fly (Bactrocera dorsalis), melon fly(Bactrocera cucurbitae), and Mediterannean fruit fly(Ceratitis capitata). The three tephritid species varied in fecundity reduction thresholds demonstrating the need to better understand how individual species may react to a specific pesticide treatment. Our results suggest that differences in vital rates as well as differential susceptibility to pesticides need to be considered when evaluating pest control options in orchard IPM schemes.

Technical Abstract: Tephritid fruit flies are economically important orchard pests globally. While much effort has focused on controlling individual species with a combination of pesticides and biological control, less attention has been paid to managing assemblages of species. Although several tephritid species may co-occur in orchards/cultivated areas, especially in mixed-cropping schemes, their responses to pesticides may be highly variable. Furthermore, predictive efforts about toxicant effects are generally based on acute toxicity, with little or no regard to long-term population effects. Using a simple matrix model parameterized with life history data, we quantified the responses of several tephritid species to the sublethal effects of a toxicant acting on fecundity. Using a critical threshold to determine levels of fecundity reduction below which species are driven to local extinction, we determined that threshold levels vary widely for the four tephritid species. In particular, Bactrocera dorsalis was the most robust of the three species, followed by Ceratitis capitata, and then B. cucurbitae, suggesting particular species responses should be taken into account when planning for area-wide pest control. Furthermore, the rank-order of susceptibility contrasts with results from several field/lab studies testing the same species, suggesting that considering a combination of life history traits and individual species susceptibility is necessary for understanding population responses of species assemblages to toxicant exposure.