The recent discovery and widespread prevalence of N. ceranae in the United States raised concerns as to whether this new pathogen is involved with increased colony losses. In order to determine if N. ceranae is present in Virginia, we initiated a statewide survey in March 2009 to determine whether N. ceranae is present and if so, at what levels. We detected N. ceranae in over 70% of colonies in Virginia, whereas N. apis was found in less than 3% of colonies, always at low levels and as a co-infection with N. ceranae. Interestingly, some of the colonies with the highest levels of N. ceranae were ranked as the strongest colonies.

Our studies on N. ceranae have helped determine the need and the most appropriate time for the treatment of N. ceranae infections. Our observations on seasonal variation of N. ceranae infections have shown significantly higher levels in April-June and lower levels in the fall and winter. Treatment with chemicals during the spring, as the major nectar flow starts, is not advisable because of the potential for honey contamination. We no longer recommend treatment for N. ceranae in the fall since winter infection levels are low and do not appear to impact colony survival.

Colony mortality due to N. ceranae infections does not appear to be a major factor in colony losses throughout the mid-Atlantic region. We do not feel that N. ceranae is a major factor associated with colony decline.

http://pubs.ext.vt.edu/ENTO/ENTO-66/ENTO-66-pdf.pdf

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