A Survey of the Incidence of Nosema Disease in California

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Abstract
California produces approximately 140,000 packages of bees and 250,000 queens annually for shipment mainly to Canada and to the northern tier of states. Samples of bees from 626 colonies in 61 apiaries indicated a light spring infection of nosema disease in 9.7% of the samples and 37.7% of the apiaries. There was no external evidence of the disease. Samples taken from 278 packages at time of shipment indicated a light infection of 5.4%. Samples from 242 package-colonies 2 to 3 weeks after installation had a light infection of 25.2%, with no external evidence of the disease. Examination of 2,088 queens from package-bee producers colonies had an infection of 1.0% while 71 queens, returned for examination, had 4.2% infected. Queens were held, experimentally, for several weeks in infected colonies and 9.1% became lightly infected. Six queens in 23 infected colonies were found to be lightly infected after several months as head of the colonies. The infection in colonies in the experimental apiary at Davis practically disappeared during the warm summer months, although it increased in artificially inseminated queen bees. Nosema disease was of little economic importance to the package-bee industry in California in 1961. Other factors were more important than nosema in the supersedure of queens.

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