Submitted to: Biocontrol
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2007
Publication Date: 2/23/2007
Citation: Riddick, E.W. Sting frequency and progeny production of lab-cultured Cotesia marginiventris. BioControl. 53(2):295-302. 2008. Interpretive Summary: The parasitic wasp Cotesia marginiventris is an important natural enemy of beet armyworms and other caterpillars that attack crops. Female wasps sting beet armyworms to produce young and the number of stings was found to not affect the number of young wasps that emerge from a beet armyworm. In addition, production of male offspring tended to decrease as the number of stings increased. Efficient rearing techniques are needed to produce large numbers of high quality wasps for release in the greenhouse or field. This research is important for maximizing the number of high quality natural enemies produced in mass rearing systems.
Technical Abstract: Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) is a solitary endoparasitoid of pestiferous noctuids. The effect of superparasitism on laboratory propagation of this species is not well known. Using sting frequency to manipulate superparasitism, I tested the hypothesis that a low level of self superparasitism (i. e., 2 to 3 parasitoid eggs per host) does not affect the production of female progeny. Young, presumably-mated, host-deprived C. marginiventris females were exposed to three Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae) early instar larvae, one at a time, in Petri dish arenas, and observed as they stung these hosts once, twice, or thrice. The results indicated that approximately 90% of hosts (in all treatment groups) yielded a parasitoid mature larva, which spun a cocoon. An increase in sting frequency (from 1 to 3 stings per host) led to an increase of female progeny (from 8 to 43%) emerging from cocoons. Perhaps, inexperienced females primarily lay an unfertilized (= male) egg into the first host encountered. More fertilized (= female) eggs will be oviposited in subsequent hosts until the sex ratio of adult progeny falls within a range that typifies this species. This study has revealed that a S. exigua larva, subjected to a low level of superparasitism, can provide a suitable environment for the development of one C. marginiventris mature larva.