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Title: LETHAL AND SUBLETHAL EFFECTS OF SELECTED INSECTICIDES ON GEOCORIS PUNCTIPES

Author
item Elzen, Gary
item Elzen, Patti

Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Conservation of insect natural enemies is a desirable component of integrated pest management (IPM). Cotton, in particular, often receives several applications of insecticides that can disrupt natural enemies. Information on the toxicity and sublethal effects of various cotton insecticides to key beneficial species is therefore important in selection of compounds that will minimize mortality. An insect predator, namely, th big-eyed bug, was evaluated in spray chamber bioassays to four newer insecticides with novel modes of action. Spinosad, an insecticide for foliage-feeding insects, and the insect growth regulators methoxyfenozide and tebufenozide, were less toxic than chlorfenapyr. At high rates, tebufenozide and chlorfenapyr significantly reduced the fecundity of the big-eyed bug compared with a control. A high rate of chlorfenapyr significantly increased host egg consumption of the big-eyed bug, suggesting a possible compensation mechanism in response to toxicity. Cotton IPM is highly complex and relies on many factors. However, any understanding we can gain regarding the selectivity of pesticides will be beneficial. It is particularly important to obtain data on the newer insecticides with novel modes of action, because these may replace conventional insecticides for use on resistant pest insects. The importance of observing direct mortality and sublethal effects of insecticides on beneficial arthropods is discussed.

Technical Abstract: Adults of the big-eyed bug, Geocoris punctipes (Say), from a laboratory culture, were exposed to selected insecticides and insect growth regulators (IGR's) using a spray chamber bioassay. Male and female G. punctipes were very tolerant of methozyfenozide, tebufenozide and spinosad compared with chlorfenapyr. At high rates, tebufenozide and chlorfenapyr significantly reduced the fecundity of G. punctipes compared with a control. A high rate of chlorfenapyr significantly increased host egg consumption of G. punctipes, suggesting a possible compensation mechanism in response to toxicity. The importance of observing direct mortality and sublethal effects of insecticides on beneficial arthropods is discussed.