Varroacide Effectiveness of Polyvar Yellow^® (Flumethrin 275 mg) Preparation

Twenty bee colonies of the Carnica breed (Apis mellifera carnica L.), the Kortówka line, were allocated to the experiment. At the beginning, they were of equal strength (average of sixteen inter-combs way). The colonies were divided randomly into two groups. The first group (PY) of ten honey bee colonies was treated with the tested veterinary product according to the producer's instructions. The second group (C) of the remaining ten bee colonies was a control group in which varroosis was not treated.

The experiment was carried out, according to the modified method by Blacquière et al. (2017), after the last honey harvest during the winter feeding of bees. Lasting 107 days, it consisted of the 1^st stage - “before treatment” (3 days), the 2^nd stage - “treatment” (from day 0 to day 90 - PolyVar Yellow in the PY group) and the 3^rd stage – “after treatment” (from day 90 to day 104 - determination of the number of V. destructor fall after pouring with oxalic acid on day 90) (Fig. 1). The sticky bottom inserts with fallen mites were replaced starting from the 3^rd day before the experiment's beginning (day 3) to the 104th day, one or three times a week depending on the needs and weather, and then the parasites were counted.

Fig. 1

Examination of the varroacide effectiveness: The varroacide effectiveness was determined based on the number parasites falling on the Varroa sticky insert (Dietemann et al., 2013; EMA, 2011) and the parasite infestation rate of bees (the number of V. destructor/100 bees) before and after the treatment (Abbott, 1925; Fries et al., 1991).

All statistical analyses were carried out using the “Statistica” (No license JPZ7017977704AR-A). The means were tested using the ANOVA test and the Duncan's test on a significance level of α=0.01.

The average daily parasite fall at the “before treatment” stage in both groups did not differ statistically, 14.50 in group PY and 18.07 in group C. The average daily fall monitored at the “treatment” stage also did not differ statistically between the groups, 14.67 in group PY and 15.76 in group C. The average daily fall after pouring oxalic acid in the bee colony was 1.44 mites in group PY and 49.11 mites in group C. The differences were confirmed statistically (F_1,16=31.1003, p=0.0000) (Tab. 1).

The first month of the “treatment” stage was characterized as high and not statistically different; daily parasite fall was 41.59 in group PY and 28.36 in group C. Statistical differences in daily parasite fall were found in the second month of treatment (F_1,18=10.1818, p=0.0051) and third month (F_1,17=13.1015, p=0.0021) (Tab. 2). After the first month of PolyVar Yellow^® use, 91% of the V. destructor population in group PY fell on the Varroa-sticky insert during the “treatment” stage (Fig. 2).

Fig. 2

The average infestation rate with V. destructor at the “before treatment” stage was similar in both groups, 13.53% in group PY and 12.82% in group C, respectively. No statistical differences were found. A very low infestation rate with the parasite was found in the group PY colonies (0.52% on average) compared to those of group C (13.94%) after the withdrawal of the PolyVar Yellow^® preparation (F_1,16=21.4343, p=0.0003) (Fig. 3).

Fig. 3

The average varroacide effectiveness of the preparation calculated based on parasite fall “during treatment” and “after treatment” in group PY amounted to 97%. The average varroacide effectiveness of the preparation, calculated based on the infestation rate of bees with parasite “before treatment” and “after treatment” amounted to 95% (Tab. 3).

The group C colonies not-treated with PolyVar Yellow^® in one apiary, were strongly infected by mites (some 45%). Thus, colonies from group PY were threatened with the possibility of reinvasion, but the use of the veterinary preparation tested in them protected them.