Mosquito responses to lethal and nonlethal effects of predation and an insect growth regulator

Abstract

AbstractLethal and nonlethal effects of predation are likely to impact phenotypic traits of potential prey that elude capture. Nonlethal effects of predation on prey can include alterations in behavior or morphology in response to predation risk which may impair prey growth and fitness. The application of pesticide in mosquito control during aquatic stages can interact with predation stress and alter density and phenotypic traits of prey. Insect growth regulator (IGR) pyriproxyfen is a pesticide that mainly prevents pupal‐adult metamorphosis by mimicking juvenile hormone, whereas the larval stage is not targeted. The use of IGR can therefore act in conjunction with natural aquatic predators that target the larval stage to affect population of prey. In this study, we assessed the invasive mosquito prey Aedes aegypti responses to lethal and nonlethal effects of a combination of IGR and predatory mosquito larvae of Toxorhynchites rutilus. The combination of IGR and Tx. rutilus heavily lowered Ae. aegypti metamorphosis to adulthood more than the independent effects of IGR or Tx. rutilus. Exposing Ae. aegypti larvae to the combination shortened life span of adults after metamorphosis for both males and females, whereas control and numerical density reduction “removals” treatments lengthened life span. Our results show strong lethal and nonlethal outcomes of the combination on Ae. aegypti. These findings suggest an additional benefit, decreases adult life span, of the use of an IGR when combined with a natural predator of mosquitoes that may be exploited to improve mosquito control strategies to reduce the risk of disease transmission.