Submitted to: Journal of Entomological Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 14, 1997
Publication Date: N/A
Interpretive Summary: The beet armyworm is an important leaf feeding insect pest of cotton, and worm infestations can destroy a field of cotton. I am actively looking for methods to minimize damage by this insect while reducing the use of insecticides. The wasp, Cotesia marginiventris, is a predominant natural enemy of this pest in the south. We are considering releasing this wasp into areas infested with the beet armyworm for control of this pest. The purpose of this study was to determine if any of the insecticides were less toxic to this parasitoid. The result of the insecticide tests showed that Vydate, Larvin, Orthene, and Asana were less toxic to this natural enemy than many other insecticides currently being used in control of this pest. Selective use of the insecticides which resulted in higher survival could conserve these native biological control agents increasing their effectiveness.
Technical Abstract: The parasitoid Cotesia marginiventris (Cresson) was treated topically with minimum recommended field rates of formulated insecticides commonly used in cotton insect control. The 14 insecticides were acephate, azinphosmethyl, bifenthrin, cyhalothrin, cypermethrin, endosulfan, esfenvalerate, fipronil, methomyl, methyl parathion, oxamyl, profenofos, thiodicarb, and Pirate. Eleven of the 14 insecticides were extremely toxic to C. marginiventris, causing 92-100% mortality of adult wasps, whereas treatment with thiodicarb, oxamyl, and acephate resulted in lower mortality of C. marginiventris males and females. For both male and female C. marginiventris, thiodicarb and oxamyl were less toxic than acephate. Esfenvalerate was the least toxic pyrethroid for C. marginiventris females. Of the three insecticides used in boll weevil control (oxamyl, azinphosmethyl, and methyl parathion) oxamyl was the least toxic to C. marginiventris. Selective use of the insecticides which result in higher survival could facilitate conservation of C. marginiventris.