Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 16, 2000
Publication Date: April 1, 2001
Citation: Tillman, P.G. 2001. Factors affecting parasitization of Spodoptera exigua (Lepidoptera: Noctuidae) and sex ratio of the parasitoid Cotesia marginiventris (Hymenoptera: braconidae). Journal of Entomological Science. 36:188-198. Interpretive Summary: Outbreaks of beet armyworms can occur causing economical damage to many agricultural crops. Since Cotesia marginiventris is an important beneficial wasp that attacks beet armyworms, it is a promising candidate for a mass rearing and release program for control of beet armyworms. The first goal in utilizing releases of C. marginiventris for control of this pest is to develop methods to maximize production of wasps in the laboratory to facilitate mass rearing. In this study, it was determined that production of wasps can be maximized for C. marginiventris in the laboratory by using an ovipositional cage that allows adult females, newly emerged to 1-day-old, to be closely associated with second instar hosts.
Technical Abstract: Laboratory environmental factors hypothesized to affect production of the endoparasitoid Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) in larvae of the beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae) were examined to determine the optimum conditions for mass rearing. Highest parasitization occurred with (1) a cage that allowed adult females to be closely associated with hosts, (2) an adult female 1-day old, (3) a host:parasitoid ratio of 30:1, (4) a second instar host, and (5) a 24 h host exposure period. Sex ratio (% female) of progeny was higher with a cage that allowed adult females to be close to hosts, females 1-day old, and second instar hosts. Cage type did not influence either percentage parasitism or sex ration of progeny. In conclusion, parasitoid production and sex ratio of progeny can be maximized for C. marginiventris in the laboratory by using an ovipositional cage that allows adult females, newly emerged to 1-day-old, to be closely associated with second instar hosts.