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 (Varroa jacobsoni) in honey bee (Apis mellifera) colonies, a method for monitoring the population size of the mites was developed. The relationship between the size of mite populations (y) in full-size honey bee colonies and natural mite mortality, measured as the number of mites falling on plastic inserts (drop-down), was investigated in Danish apiaries. The results suggest that a straight linear model (y = + x) describes the relationship between the mite population present in a colony and the calculated daily number of naturally dead mites collected on inserts during either I-week or 3-week periods before sampling: The parameters of the straight line relationship between the population size and the daily mite drop-down during a 1-week period are: beta = 0.0069 and alpha = -1.858 (r(2) = 0.77, p < 0.0001). For a 3-week period, the parameters are: beta = 0.0063 and alpha = -0.403 (r(2) = 0.83, p < 0.0001). If the model input is adjusted for the brood-rearing pattern of the sampled colonies, i.e. colonies with capped brood cells covering less than one side of a comb in total (2800-3200 cells) are excluded from the input, the gt of the model is improved. In this case, the parameters 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 sampling period are: beta = 0.0071 and alpha = -0.864 (r(2) = 0.91, p < 0.0001).