DEVELOPMENT OF SAMPLING METHODS FOR ESTIMATING LEVELS OF VARROA-JACOBSONI (ACARI, VARROIDAE) INFESTATION IN COLONIES OF APIS-MELLIFERA (HYMENOPTERA, APIDAE)

Methods for estimating infestation rates of Varroa jacobsoni (Oudemans ) on adult honey bees, Apis mellifera (L.), are not well developed. We calculated 3 measures of infestation in samples of adult bees from Ne w York State and Washington, DC: (1) M/V, the ratio of the number of m ites (M) to a constant volume of bees (V); (2) M/B, the ratio of the n umber of mites (M) to the number of bees (B); and (3) MIG, the ratio o f the number of mites (M) to the wet weight of bees (G). Each measure requires a determination of the number of mites, or the number of mite s and either the number or wet weight of bees. We calculated surrogate s for these measures that are easier to obtain. An estimate (EM) of th e number of mites in each sample was made using the ether roll techniq ue. An estimate (EB) of the number of bees in each sample was estimate d from the sample wet weight (G) by using a conversion factor (bees pe r gram). Surrogates for the 3 original measures were constructed using EM, EB, and G and compared with their corresponding original measures by using the concordance correlation coefficient r(c). Values of r(c) for EM/V with M/V were 0.97 and 0.85, in New York State and Washingto n, DC, respectively. Corresponding values for EMI B with Mi B were 0.9 7 and 0.85; values for M/EB with M/B were 0.99 and 0.98; values for EM /EB with M/B were 0.97 and 0.81; values for EM/G with M/G were 0.97 an d 0.86. Infestation rates in samples obtained from the brood nest were approximately twice as high as in samples from the honey-storage area .