*3.1. Meteorological Conditions*

The average values of air temperatures, relative air moisture, and number of days with rain for each location of EA during the observed period of beekeeping season 2014 is shown in Table 2. Obviously, these harms encountered in beekeeping may indicate that this acaricidal therapy of honey bee colonies with authorised VMPs had the obtained e ffect instead of especially detrimental environmental circumstances.


**Table 2.** Meteorological conditions at di fferent apiaries.

#### *3.2. Estimating the Strength of Honeybee Colonies*

Despite the equalization of honeybee colonies before pretreatment period with respect to colony strength, some statistical differences were determined between experimantal and control groups of honey bee colonies at different estimation days (I, II, or III) at EA1, EA2, and EA5, as follows: EA1: I (*p* < 0.001; F = 9.87), II (*p* < 0.05; F = 3.32), III (*p* < 0.01; F = 3.94); E2: III (*p* < 0.001; F = 9.87); and E5: III (*p* < 0.05; F = 3.55). Variations in the average number of honey bees per group during three estimation terms are shown in Figure 2.

**Figure 2.** Honey bee colony strength differences between experimental and control groups by different estimation dates (I—blue lines, II—red lines, III—green lines) at five apiary locations: (**a**) EA1, (**b**) EA2, (**c**) EA3, (**d**) EA4, (**e**) EA5.

#### *3.3. V. destructor Mite Fall Prior to, during, and after Varroacidal Treatments*

## 3.3.1. Pretreatment Period

During the pretreatment periods the average daily mite drops in 30 honey bee colonies per apiary were: EA1, 2.76 (± 2.60); EA2, 3.04 (± 2.60); EA3, 0.80 (± 0.10); EA4, 4.32 (± 0.50); and EA5, 0.09 (± 0.10). These values did not differ significantly between the experimental groups on individual apiaries but were significantly different between EA locations (EA4, EA5; *p* < 0.001). Results are presented in Figure 3.

**Figure 3.** Natural *V. destructor* mite drop during the pretreatment period at five apiary locations (EA1–EA5).

## 3.3.2. Treatment Period

During the summer treatment period, the estimated total *V. destructor* mite mortality that resulted was significantly higher than natural mite drop. Results of summer and winter treatment (to determine the residual amount of mites) of honey bee colonies with VMPs are shown in Figure 4. Because of very low efficacy of summer treatments in all groups of experimental colonies situated on EA5 (Figure 5), the necessary follow-up autumn treatment was done at EA5 (Figure 5), and calculations of treatments efficacy was based on those mite drops (A—47.52%; B—3.11%; C—25%; D —5.18%; E—3.11%). Results of this EA were analyzed separately from those of other EAs.

**Figure 4.** Differences in the number of fallen *Varroa destructor* mites between experimental groups (A, B, C, D, E) and control groups (O), during summer (blue lines) and winter treatment (red lines); mean ± SD. (**a**) EA1, (**b**) EA2, (**c**) EA3, (**d**) EA4.

**Figure 5.** Differences in the number of fallen *V. destructor* mites between experimental groups (A, B, C, D, E) and control groups (O), during summer (blue lines) and follow-up autumn treatment (red lines), at EA5/EA5; mean ± SD.

The mean values of *V. destructor* mortality on EA1 did not differ significantly between the experimental groups (A, B, C, D, E), but it was different in comparison with the control group (*p* < 0.05; h = 14.2). Summer treatment results were significantly different from those of winter treatment (*p* < 0.05; F = 2.74). <sup>E</sup>fficacy of varoacidal treatment is presented in Table 3, and it was decreased as follows: A > E > D > C > B. Prior to winter treatment, nine of the treated honey bee colonies were dead: 3 colonies from B group, 3 colonies from E group, 2 colonies from D group and 1 colony from C group.


**Table 3.** Treatment efficacy of varroacides on different experimental apiaries.

Note: S—summer treatment; W—winter treatment; ‡, ‡‡, ‡‡‡—number of dead honey bee colonies prior to winter treatment, in particular experimental groups.

At the location of EA2, each treatment (A, B, C, D, E) induced a significantly higher (*p* < 0.05; h = 12.9) *V. destructor* mite mortality in the parallel untreated control colonies (O). The summer treatments and winter treatments (*p* < 0.005; F = 2.83) were also statistically significantly different. <sup>E</sup>fficacy of different VMP treatments (Table 3) decreased as follows: A > D > E > B > C. All honey bee colonies survived.

The mortality rates in the treated colonies of EA3 apiary were significantly different from those in the control honey bee colonies (*p* < 0.05; h = 12.77), and between the summer and winter treatments (*p* < 0.001; F = 5.79). <sup>E</sup>fficacy of acaricidal treatments (Table 3) decreased in the same order as on the EA1.

Total V. destructor mite drop after the treatments were significantly higher (*p* < 0.005; h = 16.6) than number of dead mites counted on the bottom boards hive inserts of untreated control honey bee colonies situated at EA4. Also, the differences between experimental groups were determinated (*p* < 0.01; F = 5.95), during the summer treatments. Order of VMPs treatment efficacy decreased as follows: A, C, E, D, and B.

Varroacidal efficacy of applied VMPs was significantly different for treatments of experimental honey bee colonies from groups A and B (Figure 6a), at each EA (*p* < 0.001, F = 6.933). As a consequence of nontreated honey bee colonies during the summer period, all control groups were also significatly lower regarding percentages of varroacidal efficacy. Overall varroacidal efficacy at individual EA did not differ significantly between EA1, EA2, EA3, and EA4. These results are presented in Figure 6b.

**Figure 6.** Treatment efficacy of varroacides with different active ingredients; (**a**) treatments; (**b**) locations; \*\* (*p* < 0.05); mean ± SD.
