Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 1, 2003
Publication Date: October 1, 2003
Citation: BOOHENE, C.K., GEDEN, C.J., BECNEL, J.J. EVALUATION OF REMEDIATION METHODS FOR NOSEMA DISEASE IN MUSCIDIFURAX RAPTOR (HYMENOPTERA: PTEROMALIDAE). ENVIRONMENTAL ENTOMOLOGY. 2003. v. 32(5).p. 1146-1153. Interpretive Summary: Microsporidia infect a wide range of arthropods and have been the subject of much interest as biocontrol agents. In recent years several important beneficial insects and mites have been found with these pathogens as well, raising questions abut the quality of mass-reared beneficials for field releases. Nosema muscidurafacis causes a debilitating disease of the fly parasitoid Muscidifurax raptor, reducing fecundity of this important parasitoid by as much as 90%. In this study, conducted at USDA's Center for Medical, Agricultural and Veterinary Entomology in Gainesville, FL scientists evaluated methods for controlling this disease. Treatment of parasitoid eggs or pupae with radiation was either lethal to the parasitoids or failed to reduce infection rates. Heat shock was effective at several temperatures & exposure times. A 5-h exposure to 45oC resulted in no infection in the resulting adult parasitoids. Rearing at elevated temperatures for 3 generations resulted in decreased spore loads in infected parasitoids but did not reduce infection rates. Treatment of adult parasitoids with 3% albendazole and/or rifampicin blocked many of the parasitoids from transmitting the disease to their offspring. Cured parasitoids lived longer and produced over twice as many female progeny as infected parasitoids. These methods provide commercial insectaries and researchers with simple, inexpensive disease management strategies.
Technical Abstract: Several methods were investigated for managing Nosema disease in the parasitoid Muscidifurax raptor Girault and Sanders. Treatment of parasitoid eggs or pupae within host puparia with gamma radiation from a cesium-137 source were either lethal to the parasitoids at all dosages tested (eggs) or failed to reduce infection rates (pupae). Exposure of parasitoid eggs within host puparia to heat was effective at several temperature and exposure times. Optimal results for disease reduction was a 5-h exposure to 45oC, which resulted in no infection in the resulting adult parasitoids. Continuous rearing at elevated temperatures (30 and 32oC) for three generations resulted in decreased spore loads in infected parasitoids but did not reduce infection rates. Incorporation of the drugs albendazole and rifampicin into rearing media of the parasitoid's host (house fly immatures) resulted in pupae that were of poor quality and did not reduce infection rates in parasitoids that developed in flies reared on drug-treated media. Treatment of adult parasitoids with 3% albendazole and/or rifampicin resulted in decreased rates of transovarial transmission of the disease. Transmission blockage was required 3-7 days of exposure to the drug before substantial treatment effects were manifest. Parasitoids that fed for 7 days on rifampicin-treated honey transmitted the disease to 57.7% of their progeny compared to a 99.1% transmission rate among untreated parasitoids. An uninfected colony of M. raptor was established by pooling cured parasitoids from heat shock and drug treatment experiments. Parasitoids from the uninfected colony lived longer and produced over twice as many female progeny (201.2) as infected parasitoids (85.2).