Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 19, 1997
Publication Date: N/A
Interpretive Summary: To develop safe and effective alternatives to the use of environmentally hazardous pesticides, scientists at the Insect Attractants Laboratory in Gainesville, Florida are developing means of biological control. Currently, rearing the parasitoid, Microplitis, on the typical host species, for large-scale pilot tests is cost prohibitive Because of the potential use of Microplitis croceipes as a biological agent in pest management programs, research has focused on finding an alternate host that is less expensive to rear and on which the parasitoid could also be reared. To successfully develop an alternate host, a polydnavirus injected into the host by the female wasp must successfully alter the growth and development of the host for the benefit of the parasitoid. The virus associated with the parasitoid inhibited growth and development of an atypical host, the Greater wax moth, similarly to the natural host. This information contributes to our understanding of the factors responsible for defining the narrow range of host species on which Microplitis can successfully develop.
Technical Abstract: Polydnaviruses of many braconid and ichneumonid endoparasitoids play an important role in the successful parasitism of their hosts. The host's development is altered and its immune response is also suppressed. Calyx fluid (polydnavirus) from the reproductive tract of Microplitis croceipes, either injected alone or in combination with venom, increased the developmental period and reduced larval growth, emergence, and the average weight of adults of the natural host, Helicoverpa zea. Venom alone had only a minor effect on larval growth. Both of the biological materials were also active in the atypical host, G. mellonella. Calyx fluid and venom, injected alone or in combination, reduced larval growth, pupation, emergence, and average adult weight. In contrast, in the atypical host Spodoptera exigua, calyx fluid and venom had a minimal effect on larval growth; however, the developmental period was increased and the average adult weight was reduced when they were injected in combination. Total hemocyte counts were significantly higher in H. zea and S. exigua but remained unaffected in G. mellonella after injection of virus plus venom.