At VIHC, we have tried various different treatments to combat Varroa. The methods we’ve tried include ‘drone removal’, a biomechanical approach to remove drone brood — Varroa’s favorite food — and thereby kill mites feeding on the brood. We have also tried applying formic acid, sugar spray and sugar powder, and alcohol.
By far the most effective treatment was formic acid, applied using Mite Away Quick Strips (MAQS). This method works by lowering the pH level in the hive — which the bees can tolerate but the mites cannot. MAQS effectively fumigate the hive and, while temporarily uncomfortable for the bees, there appear to be no long term negative side effects. After studying formic acid treatments over two years, Villalobos reported that the bees’ reaction subsided significantly while mite mortality levels remained constant.
The single biggest lesson we have learned over the past two years, is that it’s crucial to keep our bees strong and clean. Thus, treating the bees with sugar yielded surprisingly positive results, presumably because it incentivized grooming and cleaning behavior.
An additional treatment approach we’ve tried most recently, involves stock improvement — or selecting for bees with particular hygienic behavior effective against varroa, attributed to a set of ‘Varroa Sensitive Hygiene’ genetics. Known as ‘VSH’, this desired hygienic behavior is a specific trait, allowing the bees to recognize that a mite has crawled into the honeycomb cell where a bee pupa is developing, then open up the cell and clean it out by cannibalizing the pupa, thereby destroying the mite.
VSH behavior was first documented in the 1960s at Ohio State University, where researchers discovered that one gene is responsible for uncapping the cell, and a second for removing the larva. These VSH genes are present in the honeybees genome, but tend to be expressed at a low frequency. Rather than being dominant or recessive, VSH genes seem to be expressed proportionally, as a percent of the VSH present in the parent bees; with 100% VSH, one can hardly find any mites in the hive.
The theory behind this phenomenon is that Varroa probably existed millions of years ago, and was effectively combated through natural selection. Over time, Varroa disappeared, and bees no longer needed to express their Varroa resistant genes. But the genetic diversity providing the potential to combat Varroa remained hidden in the honeybee genome.
This summer, Tom and Suki Glenn of Glenn Apiaries in California visited several Hawai‘i Island beekeepers, including VIHC, to artificially inseminate queens with semen from VSH drone bees. The Glenns explained that artificial insemination is essentially an acceleration of natural selection.
This summer was the Glenns fourth visit to Hawai‘i Island in two years. Their idea is to continuously inseminate with VSH semen, to reach VHS levels of nearly 100%. Bees with a high percent of VSH genes also seem to prevent other diseases, such as foulbrood, chalkbrood, and the small hive beetle. From the Glenns experience, artificial insemination has been very successful: with VSH bees, they have not had to treat their hives since 2001.Their work is helping to diversify the gene stock now present in Hawai‘i, by introducing and selecting for new genes.
Beekeeping is still a joyful, if a more complex, activity. At our Beginning Organic Beekeeping course this summer — which we co-taught with Bee Love Apiaries — we mirrored the complexity of modern beekeeping with an amazing array and interplay of different perspectives and viewpoints about if, and how, to treat for bee diseases.
Organic Varroa Management & Beekeeper Education in Hawai‘i project sponsored by:
This project was funded by a grant from the Western Sustainable Agriculture Research and Education Program.