MONITORING METHOD AS A BASIS FOR NEED-BASED CONTROL OF VARROA MITES (VARROA-JACOBSONI) INFESTING HONEY-BEE (APIS-MELLIFERA) COLONIES

To avoid excessive use of pesticides in controlling varroa mites (Varr oa jacobsoni) in honey bee (Apis mellifera) colonies, a method for mon itoring the population size of the mites was developed. The relationsh ip between the size of mite populations (y) in full-size honey bee col onies and natural mite mortality, measured as the number of mites fall ing on plastic inserts (drop-down), was investigated in Danish apiarie s. The results suggest that a straight linear model (y = + x) describe s the relationship between the mite population present in a colony and the calculated daily number of naturally dead mites collected on inse rts during either I-week or 3-week periods before sampling: The parame ters of the straight line relationship between the population size and the daily mite drop-down during a 1-week period are: beta = 0.0069 an d alpha = -1.858 (r(2) = 0.77, p < 0.0001). For a 3-week period, the p arameters are: beta = 0.0063 and alpha = -0.403 (r(2) = 0.83, p < 0.00 01). If the model input is adjusted for the brood-rearing pattern of t he sampled colonies, i.e. colonies with capped brood cells covering le ss than one side of a comb in total (2800-3200 cells) are excluded fro m the input, the gt of the model is improved. In this case, the parame ters for the 1-week sampling period are: beta = 0.0075 and alpha = -1. 184 (r(2) = 0.88, p < 0.0001), and the parameters for the S-week sampl ing period are: beta = 0.0071 and alpha = -0.864 (r(2) = 0.91, p < 0.0 001).