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United States Department of Agriculture

Agricultural Research Service

Title: Biology, Impact and Management of Nosema Disease in Hymenopteran Parasitoids

item Geden, Christopher

Submitted to: Proceedings of the International Society of Hymenopterists
Publication Type: Proceedings
Publication Acceptance Date: August 1, 2003
Publication Date: August 1, 2003

Interpretive Summary: This is a summary of an invited talk given at the International Congress of Hymenopterists in Beijing, China in July 2002. Nosema disease of parasitoid wasps is a serious problem affecting the use of these biological control agents in insect IPM programs and has been studied extensively by scientists with USDA's Center for Medical, Agricultural and Veterinary Entomology. Because the disease is transmitted from infected mother wasps to their offspring, this biological link is the best place to block the disease. Treating infected female wasps with antibiotics or exposuring them to high temperatures are two effective ways to block transmission of the disease from mothers to offspring.

Technical Abstract: Nosema infections are an emerging problem in colonies of parasitic Hymenoptera. Infection rates are typically low in the field but are rapidly amplified under mass-rearing conditions because of horizontal transmission within superparasitized hosts and the high efficiency of maternal transmission. Infected parasitoids can have shorter lifespans, longer development times and reduced fecundity compared to healthy individuals. Mass-releases of diseased parasitoids can result in the introduction of massive levels of disease into natural systems where such diseases are otherwise rare. Infections are easily detected and can be prevented in colonies by good sanitation practices during initial colony establishment. The Pasteur method can be used to eliminate disease in colonies where infection rates are low to moderate. Differences in development times between healthy and infected parasitoids can also be exploited in Muscidifurax raptor by using diagnostic windows of development times in which high proportions of healthy parasitoids are expected to emerge. This approach is ineffective for Tachinaephagous zealandicus because development times of this species are not affected by infection. Similarly, heat shock is an effective disease management tool for M. raptor but not T. zealandicus because the latter species cannot tolerate heat shock regimens that have therapeutic value. Treatment of immature parasitoids with gamma radiation kills the parasitoids before any therapeutic effect of treatment can be detected. Maternal transmission can be partially blocked by allowing parasitoids to feed on honey treated with 3% rifampicin (M. raptor, T. zealandicus and Encarsia) or albendazole (M. raptor). Drug treatment can be followed up by application of the Pasteur method to eliminate disease in colonies.

Last Modified: 4/22/2015