Effects of Insecticides on Nilaparvata lugens1 and its Predators: Spiders,2Microvelia atrolineata,3 and Cyrtorhinus lividipennis4

Abstract

Thirty-five insecticides used on rice in Asia were tested in the field against Nilaparvata lugens. The most important predators of the pest, Cyrtorhinus lividipennis, Microvelia atrolineata, and predacious spiders, Lycosa pseudoannulata, Tetragnatha, and Araneus species, were also monitored in the test plots. Ten insecticides significantly reduced numbers of N. lugens, but propoxur and ethylan gave the most consistent and effective control. Most insecticides did not significantly reduce populations of spiders and M. atrolineata compared with untreated checks, but they did reduce numbers of C. lividipennis. Fifteen treatments caused resurgence of N. lugens, resulting in significantly higher numbers in the treated plots than in untreated checks. Resurgence was apparently not caused by the toxicity of the materials against predators. Eleven of the insecticides had no effect on N. lugens.