Relative effect of four characteristics that restrain the population growth of the mite Varroa destructor in honey bee (Apis mellifera) colonies

This study was conducted to determine the existence of phenotypic and genotypic variation in the ability of honey bee colonies to restrain the population growth of the mite Varroa destructor Anderson and Trueman, and to asses the relative effect of four characteristics that may confer tolerance to honey bees toward the mite. Fifty-eight colonies infested with an equal number of mites were sampled monthly during six months to determine their levels of infestation on adult bees and in worker brood. At the end of this period, 16 colonies were selected to study the effect of grooming behavior, hygienic behavior, brood attractiveness, and host-induced non-reproduction. The infestation-levels in adult bees varied significantly between colonies (range: 6.6-44.7%), but no differences were found in the brood infestation levels. The variation between colonies was partially genetic in origin. Grooming behavior explained most of the variation (r(2) = 0.38). Negative correlations were found between the mite population growth and both the total number of mites and the number of injured mites collected from the bottom-boards (r = -0.65 and r = -0.76, respectively). Differences were found for hygienic behavior but the effect of this mechanism was not clear. No differences were found among colonies for brood attractiveness, or for the effect of the brood on the mite's reproduction.