Effects of Cool Temperatures on Oviposition and Development of Cotesia marginiventris (Hymenoptera: Braconidae)

Abstract

C. marginiventris, an abundant parasitoid of noctuids in summer, practically disappears from fall to spring in northern Florida, when the cabbage looper (Thichoplusia ni (Huibner)) can become a serious problem in crucifers. Temperature might be a limiting factor for the efficiency of C. marginiventris. In the present study we attempted to evaluate the oviposition performance of C. marginiventris and its development at different temperatures. We used cabbage looper and beet armyworm (Spodoptera exigua (Htibner)) as hosts to determine if the time of parasitoid development differs in hosts with different growth rates. C. marginiventris used in this study were obtained from the Mississippi State University rearing facility. Both host species were from 1.5 year-old colonies maintained on pinto bean-based diet (Guy et al. 1985) at USDA-ARS, Gainesville, Florida. First- and second-instar larvae of either beet armyworm or cabbage looper were offered in clusters of 100 to C. marginiventris females. The larvae on individual leaves of pigweed (Amaranthus sp.) were placed in transparent 400 ml plastic containers, with a top of nylon screen. Females of C. marginiventris were chilled to 10?C and a