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Title: Negative evidence for effects of genetic origin of bees on Nosema ceranae, positive evidence for effects of Nosema ceranae on bees

item Villa, Joseph
item Bilodeau, Lanie
item Danka, Robert

Submitted to: Apidologie
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2013
Publication Date: 2/14/2013
Citation: Villa, J.D., Bourgeois, A.L., Danka, R.G. 2013. Negative evidence for effects of genetic origin of bees on Nosema ceranae, positive evidence for effects of Nosema ceranae on bees. Apidologie. 44(5): 511-518. DOI: 10.1007/s13592-013-0201-1

Interpretive Summary: The parasitic microsporidian Nosema cerane, originally from Southeast Asia and now widespread in the United States, is of concern to beekeepers. Unfortunately, negative effects on colonies are not consistent in reports from other countries and even within North America. We followed the infection with the parasite in honey bee colonies of diverse genetic origins in two sites in southern Louisiana to look for possible genetic resistance to the parasite and for effects of the parasite on the survival and health of colonies. The different genetic origins of colonies did not translate into differences in parasitic infection. However, the level of infection of colonies did show a debilitating effect on the condition of colonies. While high infections did not consistently kill colonies, more highly infected colonies grew more slowly or declined in population. Beekeepers in the United States should monitor the levels of infection and consider taking corrective actions to prevent weakening of colonies at times when the levels of infection increase.

Technical Abstract: Colonies of different origins were sampled monthly to detect possible differential infection with Nosema ceranae, and colony sizes and queen status were monitored quarterly. One experiment used queens from colonies with high and low infections instrumentally inseminated with drones of the same type. A second experiment used queens from ten commercial sources. No clear genotypic (P=0.6817) or phenotypic (P=0.623) differences in infection were evident. Colony deaths and supersedures did not relate significantly with infection except for deaths of colonies in the autumn (P = 0.02). Significant effects on colony growth were found in all seasons: average quarterly decreases in population ranged from 0.4 to 1.4 frames of bees per million N. ceranae per bee. While these results suggest that breeding for resistance may require more intense selection, larger base populations, or different screening methods, they confirm that N. ceranae can be involved in weakening of colonies even in warm climates.