Development of Cotesia orobenae Forbes (Hymenoptera: Braconidae) in its Host, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae)

Abstract

Temperature and host density effects on the development of Cotesia orobenae Forbes (Hymenoptera: Braconidae), and its parasitism of the cross-striped cabbageworm, Evergestis rimosalis (Guenée) (Lepidoptera: Pyralidae), were investigated. Time for adult parasitoid emergence from cocoon masses of C. orobenae maintained at 15, 20, 25, 30 and 35°C and a photoperiod of 15:9 (L: D) was inversely related to temperature. Parasitoid emergence exceeded 86% for all temperatures except that at 35°C. Development of C. orobenae on early-instar hosts was best at 20 and 25°C. Although the shortest developmental time was observed at 35°C, survival of both parasitoid and host was low at this temperature. At 15°C, the parasitoid was not very active, and developmental time was the longest among the temperatures tested. Percent of host larvae parasitized was significantly higher at 20 and 25°C than the other temperatures tested. Females were short-lived and oviposited an average of 118 and 136 eggs at 20 and 25°C, respectively. Females died after 24 h of being placed in the oviposition chamber at 30 and 35°C. At 15°C they lived longer, but did not parasitize host larvae provided. Virgin females produced only male progeny. Mated females produced slightly more female offspring than males. Sex ratios of progeny from females paired with single or multiple males were not different. Percentage parasitization of host larvae between treatments differed for the first day, but not the second day. Fecundity of C. orobenae exposed to five host densities (5, 10, 15, 20, and 25 per parasitoid) showed significant differences in percent parasitization among the treatments. Percentage parasitization was highest with five and 10 hosts per parasitoid. The highest number of parasitoid cocoons recovered per cocoon mass was obtained with 10 hosts. The data indicate that optimal temperature for C. orobenae oviposition, development, and parasitism of its host is between 20 to 25°C.