Friday, September 1, 2017

Sampling Varroa Mites

Varroa mites are the greatest pest killer of honey bees. If left unchecked, these parasites will kill a colony of bees in about 18 months. It is, therefore, necessary for beekeepers to be aware of the mite load that a hive carries and to take corrective action when mite numbers exceed critical levels. Varroa mites live in bee hives, and they reproduce in the sealed brood cells of the pupal stage of honey bee brood. Mite levels typically peak in late summer at the time that queen bees slow their rate of egg laying. Excessive numbers of Varroa mites in the hive often lead to colony death. Mites weaken individual bees by sucking the bee’s blood, known as hemolymph. When a mite pierces the exoskeleton of a honey bee, it passes numerous viruses to the bee. At least 15 Varroa-vectored viruses have been identified. Varroa mites and the viruses that they transmit lessen the life span of the bees, leading to smaller winter colony clusters. These smaller clusters are often unable to generate enough heat to survive the winter.

Some individuals ignore the threat of parasitic mites and lose their bee. Others attempt to kill the mites with harsh chemical treatments. They are usually successful in reducing the colony mite loads, however, repeated use of harsh chemicals leads to populations of mites that are resistant to the chemicals. Beekeepers who take a judicious approach to controlling parasitic mites develop their own Integrated Pest Management program that involves mite sampling and treatments as necessary. The Honey Bee Health Coalition offers Tools for Varroa Management: A Guide to Effective Varroa Sampling & Control as a free document. The guide and video demonstrations of Varroa control techniques may be downloaded from There are several methods of sampling a bee hive’s mite levels, including powdered sugar rolls and alcohol rolls. In today’s photo, Rita is counting the number of Varroa mites on 300 bees using a simple alcohol roll test.

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