Three year survey of varroa mite and tracheal mite infestations of honey bees in Wisconsin

A three-year survey of varroa and tracheal mites in Wisconsin showed that the number of colonies infested with varroa and/or tracheal mites remained fairly constant. Mortality of colonies that were wintered in Wisconsin was very high, with 44% during winter of 1992/1993, 45% in 1993/1994, and 29% during 1994/1995. The varroa mite infestation levels of most colonies were greater than 1% between 1992 and 1995. Colonies with varroa infestation levels greater than 1% in fall (>2 mites/200 bees ether roll test) suffered higher winter mortality. At the same time tracheal mite infestation levels of most colonies stayed below 10% with no apparent effect on overwintering. Colonies treated in spring before honey flows and in fall after honey flow, wintered much better than colonies treated only once annually.