Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/25/1999
Publication Date: 3/1/2000
Citation: Stapel, J.O., Cortesero, A.M., Lewis, W.J. 2000. 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. Biological Control. 17:243-249. Interpretive Summary: Biological control of plant feeding pests of agricultural crops by beneficial insects is a crucial component of Integrated Pest Management (IPM) strategies. Chemical pesticides often disrupt the effectiveness of these beneficial agents, thus a better understanding of pesticide/natural enemy interactions is vital to effective IPM. ARS scientists at Tifton, GA Ademonstrated that systemic pesticides often used on cotton crops can have major indirect sublethal effects on parasitic wasps through contamination of extrafloral nectar on which these beneficial wasps regularly feed. The pesticide-laden nectar seriously hampered the effectiveness of the wasps in their experimental tests by reducing their longevity and host foraging ability. These studies and related research is targeted toward developing a better understanding of such indirect, sublethal effects and methodology for minimizing pesticide impact on beneficial organisms.
Technical Abstract: In IPM programs it is important to determine which insecticides are compatible with biological control and what are the possible disruptive effects to beneficial insects. Unfortunately, predictions on the compatibility of an insecticide with biological control often are based on incomplete screening tests. While mortality through direct insecticide exposure is a very common screening method, possible sublethal effects as result of either 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 ability and longevity of the parasitoid Microplitis croceipes Cresson (Hymenoptera:Braconidae) after feeding on extrafloral nectar from cotton (Gossypium hirsutum L., Malvaceae) plants that were treated with systemic insecticides. The insecticides used in this study are regularly used in cotton growing areas in the United States. For all tested insecticides longevity of M. croceipes females that fed on nectar from treated cotton plants was reduced for at least 10 days after insecticide application. Moreover, the parasitoid's host foraging ability was severely affected, ranging from 2 days (imidacloprid) to 18 days (aldicarb) after insecticide application. The consequences of these sublethal effects on the success of biological control and possible ways to minimize exposure of beneficial insects to insecticides are addressed.