Predatory Abilities of The Backswimmer Buenoa Amnigenus Are Not Impaired After Sublethal Exposures To Pyriproxyfen

Pyriproxyfen is a juvenile hormone analogue that is commonly used to control the immature stages of mosquitoes in both artificial and natural water reservoirs. Recently, concerns have been raised regarding the pyriproxyfen community effectiveness in preventing vector-transmitted diseases. Such concerns have been based on the unintended effects on non-target organisms and selection of resistant mosquito populations. Thus, this investigation was conducted aiming to evaluate the toxicity of pyriproxyfen to Aedes aegypti (Diptera: Culicidae) larvae and the backswimmer Buenoa amnigenus (Hemiptera: Notonectidae), a naturally occurring mosquito larvae predator. We also assessed the abilities of backswimmers exposed to sublethal levels of pyriproxyfen to prey upon mosquito larvae (L2) under three larval densities (3, 6, or 9 larvae/100 mL of water) using artificial containers. Our results revealed that pyriproxyfen killed backswimmers only at concentrations higher than 100 mg active ingredient [a.i.]/L, which is 10 times higher than that recommended for larvicidal field application (i.e, 10 mg a.i./L). Interestingly, the abilities of backswimmers exposed to sublethal levels of pyriproxyfen (100 mg a.i./L) to prey upon mosquito larvae were not affected. Harmful effects on the backswimmer predatory abilities were detected only at concentrations of 150 mg a.i./L and when there was a higher prey availability (i.e., 9 larvae/100 mL of water). Together, our findings indicate that the reduced community effectiveness of this insecticide derives from factors other than its detrimental effects on non-target organisms such as the backswimmers.