Field Test of Resistance to Acarapis woodi (Acari: Tarsonemidae) and of Colony Production by Four Stocks of Honey Bees (Hymenoptera: Apidae)

Abstract

Characteristics of four stocks of honey bees, Apis mellifera L., were evaluated in colonies managed commercially for honey production at three U.S. locations―one north-central location (Iowa) and two south-central locations (Mississippi, Texas). Stocks were compared for 1 yr beginning in October 1991 to determine the levels of infestation by tracheal mites, Acarapis woodi (Rennie), and to ascertain survival rates, levels of honey production, and sizes of adult and brood populations. Test stocks were ARS-Y-C-1 ( A. mellifera carnica Pollman, imported from Yugoslavia), Buckfast (imported from the United Kingdom), Survivor (developed from colonies in a Louisiana apiary believed to have had severe tracheal mite infestation), and Unchallenged (developed from a feral Louisiana population never exposed to tracheal mites). Stocks initially were represented by 15-20 colonies at each location. After an initial inoculation of mite-infested bees in the autuinn, infestation percentages increased more markedly in the susceptible (Survivor and Unchallenged) stocks than in the resistant (ARS-Y-C-1 and Buckfast) stocks. Mean infestation percentages in the resistant stocks remained <15% and thus were below levels associated with economic damage. Mean infestation percentages in susceptible stocks ranged from 13 to 95% at each site during the final 6 mo of the study Numbers of mites per infested bee differed between stocks in 4 of 21 samples; mite numbers tended to be greatest in Survivor bees and least in Buckfast bees. Mortality increased more rapidly among susceptible colonies than among resistant colonies as infestation increased in 1992. Honey production was greatest by Buckfast, intermediate by Survivor, and least by Unchallenged and ARS-Y-C-l colonies. Differences in population sizes of adult bees and brood occurred in approximately half of samples taken in spring and autumn; Survivor and Buckfast colonies were most populous. Stock characteristics showed no interaction of genotype with environment, i.e., location. Our results support the feasibility of an approach using genetically regulated resistance to manage problems caused by tracheal mites.