In the previous article, we wrote about the factors that cause the suppression of the Varroa mite population in our Sunny Hive. 90% of these factors are related to the effect of elevated temperatures on the eggs and nymphs of the mites in the sealed brood, which unable to escape from the effects of high temperatures, while adult mites can leave the hive along with the bees on which they parasitize. And the effect of temperatures up to +45C on adult mites is not as strong as on their brood.
As we said earlier, the method of thermal action on mites is not new. Only there was no understanding of the reasons for the suppression of Varroa mites population, which we outlined in our previous works, and, most importantly, there was no simple and cheap mechanism for creating high temperatures in the hive.
It would seem that there is nothing complicated about it? But, as it turned out, a combination of many hive design factors is required to achieve the required conditions. The most important thing is that this combination of technical elements should allow the hive to heat up quickly and efficiently enough and at the same time not allow the bees to cool the hive. It took us five years of experiments to find the perfect combination. And now, for the second year, the hive has been showing very good results. Bees can live in it without any acaricide treatment, winter well and develop well in the spring.
What is needed for the hive to work? Of course, warm and sunny days. It is not for nothing that we called it the Sunny Hive. Creating conditions unfavorable for the reproduction of Varroa mites is possible already at an outdoor temperature + 17-20C. High efficiency of suppressing their development begins at an outdoor temperature of + 22-25C. Maximum efficiency at + 35C. At higher temperatures, the work of the Sunny Hive should be limited by using shading elements of its design.
Spring 2025 become another time to test the efficiency of the hive. In April, the outside temperatures were up to +20-25C and the sun was shining on these days. The conditions were ideal for the hive. This year, in one of the hives of our experimental apiary, which contains a bee family that was not specially treated during 2024, we installed a temperature logger, and now we receive a continuous flow of data on the temperature in the nest. The logger sensor is installed in the alley between the brood frames.
The results we received from the logger confirmed our assumptions about the strength and duration of the impact of elevated temperatures. In the figure, you can see excerpts from the graph, which contains the most effective impacts for April 2025.
The target indicators of the hive - that is, the negative impact on the brood of mites, were achieved at least five times, and four more times the indicators were achieved that violate the comfortable mode of reproduction of mites. Of all this, the temperatures twice approached +38-39C , which has a significant negative impact on the mites brood, and it lasted for about 2-2.5 hours. And three times the temperatures reached about +37C, which lasted for about 4.5-6 hours.
According to the information obtained by scientists, such a temperature range leads to the death of 50% to 95% of the mites brood in sealed cells. We believe that the duration of exposure ensured the heating of the combs to the same temperature as the air temperature in the brood part of the hive.
However, the final result will become clear after the next alcohol wash from the worker bees. We washed off Varroa mites from all colonies of the experimental apiary in the fall of 2024 and in March 2025 and the next one will be done at the end of spring season. The final wash will be done at the end of brood rearing period in the fall of 2025.
We believe that the result will be as good as in 2024.
