Full article -> http://forum.beemaster.com/index.php?ac ... attach=481Temperature seems to have more of an impact on Varroa reproduction than most people thought. While 95ÂºF is "brood nest temperature," that temperature fluctuates some with climatic conditions. By carefully controlling temperature, Varroa were found to reproduce best at 93ÂºF. Performance was a bit worse at 88-91 and 95Âº. At the lower than brood nest temperatures, the post-capping period is extended about one day per 2ÂºF. At higher temperatures the post-capping period is not shortened significantly. However, at "brood nest" and higher temperatures, mite reproduction drops way off. In the same study it was shown that 53% of the mites on brood held at 59-68% RH (normal) reproduced normally but at humilities of 79-85% only 2% of the mites reproduced. Hot, humid brood nests are tough on Varroa. Studies of Apis cerana brood nests showed drone brood is reared at 92ÂºF (perfect for Varroa) and worker brood is incubated at 96-98ÂºF (too hot for Varroa). Purposely cooling the brood nest in Apis mellifera colonies by using a "thin" hive lid, open bottom board, simulative feeding to spread brood out, and splitting the brood nest with frames of foundation doubled the numbers of mites on the bees.
Full article -> http://forum.beemaster.com/index.php?ac ... attach=482The antivarroa bottom board must never be used with its bottom hole opened as this leads to a lowering of cluster temperature resulting in ideal conditions for varroa development. As confirmed in 2000, this situation not only negated the beneficial effects of the bottom board, it also resulted in a net increase in the mite infestation rate (29.2% more varroa mites, non significant) as compared to the control group.
Heat may be an answer, but I think this particular method is a little complicated for the results of just killing the mites in one frame. Not to mention the issue with wax melting. Why not heat the whole hive and get the most bang for the buck -> http://robo.bushkillfarms.com/downloads ... omBees.pdf
Heat and humidity retention is the main reason I have gone away from screened bottom boards. All the feral hives I remove have all the cracks sealed up as tight as can be. So far I have had good results, stronger spring build up and haven't treated for varroa in 3 years.
Full article -> http://forum.beemaster.com/index.php?ac ... attach=481
Full article -> http://forum.beemaster.com/index.php?ac ... attach=482