124 PESTICIDE EFFECTS ON INSECT NATURAL ENEMIES OF COTTON PESTS John R. Ruberson and Phillip M. Roberts Department of Entomology, University of Georgia, Tifton Abstract We tested the effect of selected insecticides on the parasitic wasp Cotesia marginiventris. This wasp is an important parasite of nearly all caterpillars that attack cotto. It is particularly effective against armyworms, but also is a common parasite of bollworms, budworms, and loopers. As such, it is important that we do what we can to conserve this wasp in the field, and that we understand the potential impacts of pesticide applications on its ability to function. For this study, we sprayed insecticides on wasps developing within their cocoons, as cocoons are fully exposed in the field during insecticide treatments, and are unable to escape. Further, cocoons in the field provide an important source of wasps for caterpillar biological control. We examined the effects of 6 insecticides: ?-cyhalothrin (Karate Z), dicrotophos (Bidrin), emamectin benzoate (Denim), novaluron (Diamond), and acetamiprid (Assail or Intruder). All were tested at field rates, although this was a laboratory study. Freshly-formed cocoons (< 12 h old) of C. marginiventris were collected and separated into groups. Each group of cocoons was sprayed with the designated insecticide, allowed to dry, and each cocoon was individually placed in a tissue culture tube. Treated cocoons were checked twice daily for wasp emergence. Developmental time (from treatment to adult emergence from the cocoons) and survival were recorded, and gender of emerging parasitoids was determined. After adult emergence, parasitoids were paired within the insecticide treatments to allow detailed examination of their life histories in relation to the insecticide treatments. Each pair was held in a plastic petri dish provisioned with a streak of honey. Each day, 50 beet armyworm caterpillars (24-48 h old) were added to each dish to allow the female parasitoids to sting them, and caterpillars from the previous day were removed and placed on diet, where they were held until paraisoitd emergence, or the caterpillar pupated (indicating that it was not parasitized). In this manner we were able to assess insecticide effects on wasp fecundity and, by extension, the ability of the parasitoids to locate and attack hosts. A small piece of insect diet was placed in each dish for the host caterpillars to feed on during exposure to the wasps. Developmental times of male and female wasps were affected by insecticide treatments. Development of both males and females was delayed by Karate, Bidrin, and Denim, although the delay was generally less than a single day. Survival was marginally affected by insecticides, with the lowest survival occurring in the Denim and Karate treatments. In all cases of mortality, the parasitoids died as adults within the cocoons, indicating that the insecticides did not impair pupal development.