Disruptive sublethal effects of insecticides on biological control: Altered foraging ability and life span of a parasitoid after feeding on extrafloral nectar of cotton treated with systemic insecticides

Predictions in integrated pest management on the compatibility of an insect icide with biological control often are based on incomplete screening tests . While measuring levels of mortality from direct insecticide exposure is a very common screening method, possible sublethal effects as a result of ei ther direct or indirect insecticide exposure remain relatively unknown. The impact of sublethal effects on the success of biological control can be as deleterious as mortality. Here, we report the reduced host foraging abilit y and longevity of the parasitoid Microplitis croceipes Cresson (Hymenopter a: Braconidae) after feeding on extrafloral nectar from cotton (Gossypium h irsutum L., Malvaceae) plants that were treated with systemic insecticides. The insecticides used in this study are regularly applied in cotton-growin g areas in the United States. For all tested insecticides, longevity of M. croceipes females that fed on nectar from cotton was affected for at least 10 days after plants were treated with insecticides. Moreover, the parasito id's host foraging ability was severely affected for periods ranging from 2 days (imidacloprid) to 18 days (aldicarb) after insecticide application. T he consequences of these sublethal effects on the success of biological con trol are discussed. (C) 2000 Academic Press.