Nonlethal Effects of Pesticides on Web-Building Spiders Might Account for Rapid Mosquito Population Rebound after Spray Application

Featured Application In this study, a broad-spectrum insecticide is shown to halt mosquito capture by orb-weaving spiders, even when the application does not kill the spiders. Reduced prey-capture, even temporary, can allow mosquito populations to rebound quickly. Adoption of other mosquito control methods, such as bacterial larvicides, avoids these potential problems. Spiders are important population regulators of insect pests that spread human disease and damage crops. Nonlethal pesticide exposure is known to affect behavior of arthropods. For spiders such effects include the inability to repair their webs or capture prey. In this study, nonlethal exposure of Mabel's orchard spider (Leucauge argyrobapta) to the synthetic pyrethroid permethrin, via web application, interfered with web reconstruction and mosquito capture ability for 1-3 days. The timing of this loss-of-predator ecosystem function corresponds to the rapid population rebound of the yellow fever mosquito (Aedes aegypti) following insecticide application to control arbovirus epidemics. We suggest this temporal association is functional and propose that follow-up study be conducted to evaluate its significance.