November 26th, 2019

EFFECTIVENESS OF THE COMBINATION OF ESSENTIAL OILS FOR CONTROL OF VARROA DESTRUCTOR

Authors: Prof. Kalinka Gurgulova and Dr. Vera Popova

Primavet-Sofia Ltd. is the only one company in the country that produces veterinary medicinal products for bees. As a proven company in the market oriented to the needs of the Bulgarian beekeepers, the modern tendencies for the application of natural products, their advantages over the conventional chemical acaricides and the increase of organic production, Primavet-Sofia Ltd. has focused on researching, developing and creating different combinations of essential oils (CEO) to help beekeepers in the difficult fight against varroatosis.

Combinations

Based on the literature from scientific and practical experience in the use of essential oils in the control against varroatosis, various combinations of essential oils have been developed and tested. The compatibility, solubility, homogeneity and stability of the combinations were examined. In order to determine the dose in units, it was calculated how many grams of oil contained in 1 drop of each combination. The amount of oil that the strips can absorb, the time for evaporation of the oils and their complete drying were determined.

Of all the combinations, nine were selected with different contents of essential oils. In preliminary laboratory studies we have found that the most stable and promising are three of them - combinations №3 (CEO3), №6 (CEO6) and №9 (CEO9).

Tolerance

Attempts at tolerance of bee families to strips accumulated with combinations of essential oils were carried out on an apiary located in Kozloduy, which counts 100 bee families in 12-frame beehives. The experiments were performed to test the tolerance of bees to essential oils and to account for the initial effect after 24 h. At our opinion, we left the strips until day 4, in order to follow the residual action of the oils. We tested three combinations - №3 (CЕO3), №6 (CEO6) and №9 (CEO9), each with 3 bee families with different amount of oil on the strip - 1, 2, 3 and 4 drops/strip. After dripping, the strips were placed on the frames in the hives.

Bee families have shown good tolerance for combinations of essential oils imported into beehives with strips. No negative effects were observed in the bee queen, bees and broth on the 7th, 24th hour and 4th day. There were no bee exits at the entrance to the hives, the theft of bee families and the attack of bees. There was no odor of essential oils in the apiary around the treated hives during the stay of the strips. The initial efficacy for 4 days varied depending on the degree of infestation of the bee families and the amount of essential oil on the strips - the highest effect was found at 4 drops / strip.

Efficiency

The efficacy experiments of the combinations of essential oils were carried out in 208 bee families of 11 apiaries, located in the different districts of Sofia, Montana and Pernik. The experiments were carried out according to a pre-prepared work program.

We applied the following combinations of essential oils:

- CEO3 - 1 strip with 4 drops applied and 2 tapes with 2 drops each.

- CEO6 - 1 strip with 4 drops applied and 2 tapes with 2 drops each.

- CEO9 - 1 strip with 4 drops applied and 2 tapes with 2 drops each.

The following were used as control products:

- Ecostop - lamellae, veterinary medicine product of the company "Primavet-Sofia" Ltd.

- Apigard - gel veterinary medicine product of the company "Vita Bee Health" Ltd.

The preparations were administered according to the manufacturer's instructions.

We have formed the following groups of bee families:

O1-experimental group treated with CEO3 - 10 bee families.

O2- test group treated with CEO6 - 10 bee families.

O3- experimental group treated with CEO9 - 10 bee families.

K-control group - 10 bee families not treated.

The experiments were performed on 5 families of the group with 1 strip, 4 drops each, and the remaining 5 families with 2 strops, with 2 drops of combinations. The purpose was to determine if there was a difference in the efficiency of placing the tapes with essential oils in one or two different locations.

The test was conducted in the following order:

- Determining the strength of bee families by ascertainment the number of honeybees with bees and the between frames occupied with bees.

- Clinical test of acaricidal activity against Varroa destructor - treatment with various combinations of essential oils, developed by "Primavet-Sofia" Ltd. Treatment of 1st, 7th, 14th day.

- Determining the strength of bee families by ascertainment the number of inter-frames with bees and the number of number of honeycombs occupied with bee broth after treatment.

- Control treatment with Ecostop or Apigard VMPs on the 21st day after the start of treatment according to the manufacturer's instructions.

- Reporting of the number of mites that have fallen in the control and experimental groups of:

- I treatment - 24 hours, 4 and 7 days,

- II treatment on the 8th, 11th and 14th days,

- III treatment - 15th, 18th and 21st days,

- on the 22nd day - 24 hours after the control treatment.

In the smaller apiaries with a limited number of bee families, we tested one of the combinations, and in the larger apiaries, we tested with the three combinations of essential oils. Due to the great complexity of the experiments, in some of the apiaries we collected only mites that fell from the control treatment and by their number we determined the amount of remaining mites in the family after treatment with essential oils.

During the experiments we observed the bee families for the presence of negative effect in the bee queen, bees and the broth - death of cocoons and expurgate of the broth, exit of the bees from the hive, thefts, replacement of the queen bee.

Results

The results of our studies showed a high effect in the application of the three combinations of essential oils in the Montana area. CEO3 and CEO9 have equivalent efficacy slightly higher than CEO6. Measure globally all the characteristics of the three combinations, we decided on CEO9, which has all the qualities to be used as an aid in the integrated control against varroatosis, along with other methods and products. Efficiency exceeds 90%, which is actually a requirement for registered acaricides (Figure 1).

When we tested the efficacy in bee families with less than 5 mites (Figure 2) after control treatment and those with more than 5 mites (Figure 3), we found that efficiency did not change significantly. Accordingly, for CEO3 the efficiency is increased by 4%, while for CEO6 and CEO9 - the efficiency is reduced by 2-5% in the more infected bee families.

 FIG. 1. The effectiveness of the different combinations of essential oils

 FIG. 2. Effectiveness of different combinations of essential oils - control treatment <5 mites

FIG. 3. Effectiveness of different combinations of essential oils - control treatment> 5 mites

When comparing the results of the application of CEO9 in the apiaries of the three regions (Figure 4), we found that the lowest efficiency was 87.51%, which is absolutely acceptable for essential oils such as acaricides. This is probably due to different levels of infestation of families in different regions, different beekeeping practices and different hive systems.

FIG. 4. Efficacy of CEO9 in apiaries from the three regions

When examining the effectiveness of CEO6, we found great variability in results (Fig. 5). The average efficiency was 89.79%, the minimum - 84.42% and the maximum - 93.67%. These data are also satisfactory and, following further studies, this combination may find future application in the fight against Varroa mites.

 

FIG. 5. Efficiency of CEO6 in apiaries - Sofia

The average number of other mites in the families that fell after the control treatment with Apigard is presented in Figure 6. This study was conducted in several apiaries in the Pernik region with CEO9. The data show a great variety in different apiaries. This is due to the different infestation of bee families. On average, the largest number of mites falls in apiary No.3 in the village of Begunovtsi - 20.4 mites. Comparing these data with the efficacy in infected families with> 5 mites (Fig. 3), we can state that the efficacy of CEO9 at higher infestation reaches almost 90%. The smallest number of fallen mites was found in apiary in the village of Filipovtsi, respectively 1.4 mites. We were impressed by the fact that many families did not have mites in control treatment, indicating a low degree of invasion.

 

FIG. 6. Average number of fallen mites than the control treatment with Apigard in the apiary of Pernik

FIG. 7. Fallen mites by the action of CEO9 in the apiary of Pernik

FIG. 8. Fallen mites from control treatment with Apigard in the apiaries of Pernik region

The study of the compatibility, stability, tolerability, harmlessness and efficacy of the specified combinations of essential oils in the laboratory and the apiaries continued for more than one year. As a result, we offer beekeepers a combination of essential oils - CEO9, which provides efficiencies above 80%, which, combined with other methods of year-round control of V. destructor, will help in the integrated fight against varroatosis.