OBSERVATIONS ON BEE AND VARROA MITE POPULATIONS IN INFESTED HONEY BEE COLONIES

Bee and mite populations in 6 German colonies were calculated from mid-May until the beginning of Sept. Colonies were divided into 3 groups: those with relatively few mites at the start of the experiment; those well infested; and those strongly infested. All colonies were in good shape at the start of the experiment in May. The bee population was calculated in 3 wk intervals by counting the number of natural mite mortalities and by extrapolating from infestation in adult bees and sealed brood. The mildly-infested colonies had 18,000 bees on the average, the middle-infested colonies 11,000 bees and the strongly-infested 15,000 bees at the start of the experiment at the end of May. While the population increased in the mildly-infested colonies, the middle- and strongly-infested decreased to 2500 bees by the beginning of Sept. The brood decreased in the same manner as the bee population by the end of July. At the same time, the degree of infestation of the brood, and the bees, increased drastically. The natural death of the mites increased per colony, on the average of 1500 mites/wk. The acute paralysis virus (APV) could be identified in adult bees of the collapsed colonies. The brood of these colonies exhibited clinical symptoms of European Foulbrood.