5.1. Effects on bees
HBTM can cause diminished brood area, smaller bee populations, looser winter clusters, increased honey consumption, lower honey yields and frequently, colony demise (Komejli et al., 1989). In temperate regions, mite populations increase during the winter, when bees are confined to the hive in the winter cluster. Heavy mite infestation affects bee metabolism and the ability of colonies to regulate the cluster temperature (Skinner, 2000); chilling may be a significant cause of colony death. In North America, colony losses increased shortly after first exposure to HBTM (Wilson et al., 1997). Colonies with 40-50% tracheal mite infestation or higher frequently die during the winter in northern USA and Canada (Furgala et al. 1989; Otis and Scott-Dupree, 1992). The colder the winter temperatures, the greater the probability of mortality at any mite prevalence value.
Treatments for HBTM include using vapours from menthol crystals, synthetic acaricides and oil or grease patties made from vegetable shortening and sugar. Additionally, resistant lines of bees have been developed.