Varroa destructor infestation in untreated honey bee (Hymenoptera : Apidae) colonies selected for hygienic behavior

Honey bee (Apis mellifera L.) colonies bred for hygienic behavior were test ed in a large field trial to determine if they were able to resist the para sitic mite Varroa destructor better than unselected colonies of "Starline" stock. Colonies bred for hygienic behavior are able to detect, uncap, and r emove experimentally infested brood from the nest, although the extent to w hich the behavior actually reduces the overall mite-load in untreated, natu rally infested colonies needed further verification. The results indicate t hat hygienic colonies with queens mated naturally to unselected drones had significantly fewer mites on adult bees and within worker brood cells than Starline colonies for up to 1 yr without treatment in a commercial, migrato r beekeeping operation. Hygienic colonies actively defended themselves agai nst the mites when mite levels were relatively low. At high mite infestatio ns (> 15% of worker brood and of adult bees), tile majority of hygienic col onies required treatment to prevent collapse. Overall. the hygienic colonie s had similar adult populations and brood areas, produced as much honey and had less brood disease than the Starline colonies. Thus, honey bees bred f or hygienic behavior performed as well if not Letter than other commercial lines of bees and maintained lower mite loads for up to one year without tr eatment.