As winters go, it has not been a bad one for us human beings. Weatherwise, I don’t think it has been that bad for bees, either. Temperatures have been a bit up and down, but overall they haven’t had to cope with prolonged bitter cold. However, reports are coming in where some beekeepers’ bees are doing fine and other beekeepers are losing many of their hives.
This is the same pattern I have seen for several years. It also is reflected nationally with losses over the last 10 years ranging from 29 percent to 50 percent per year. Every year we lose hives to many different causes, including extreme weather, certain diseases, starvation and predators, but these have always been an issue.
The parasitic varroa mite has been a real problem for beekeepers, and it seems to be getting worse. It is becoming vital to treat for mites and check to see whether the treatments have worked.
Mites have a peculiar life cycle that allows them to quickly build up a population of mites resistant to certain treatments. It seems that some of the best organic treatments I have been using to treat mites, such as Mite Away Quick Strips (formic acid) and Hop Guard have been giving more variable results than in the past. They still work well but not in every case completely. It is, therefore, important that beekeepers check for mite levels after treatment as well as just as a means to tell us if the hive needs to be treated in the first place.
Hive death because of mites is not just because the mites themselves damage the bees. Like a tick, mites infect their hosts with a variety of viruses. There are about 20 identified viruses passed to bees by mites. Colonies can generally cope with low or modest mite and virus loads in the spring and summer when weather is nice, and food is plentiful. Like us shaking off a cold, the colony can shake off mild virus infections if everything else is OK. However, if we are stressed a cold can develop into something much worse. Honeybee colonies respond in the same way. In fall the weather gets colder and food becomes more scarce, which stresses the bees, leaving them less able to fight off viruses. Colony death ensues.
I suspect last summer and fall’s drought stressed out our bees more than most of us realized, making our colonies far more vulnerable to viruses. It is also possible that mites are carrying more virulent viruses. Time and further research will tell.
One thing is for sure: It has never been more important to treat colonies for mites to avoid high levels building up. One new mite treatment was approved for use in Maine about two years ago. Last year was my first opportunity to use oxalic acid on my bees. Oxalic acid can be administered either mixed with sugar syrup and drizzled over brood frames or applied as a vapor. This requires a heating device, which heats up a measured quantity of acid crystals inside the hive until vaporization occurs. The vapors are contained in the hive for 10 minutes by covering the entrance with a towel. The vapors cool and form microscopic crystals in the hive and on the bees which kill the mites and — unlike some of the other treatments — not the bees.
This should only be done when honey supers have been removed from the hives. I tried this on more than half my hives last fall. These hives had previously been treated for mites in late summer and early fall. I was quite shocked to see that about one in three of these previously treated hives showed a very high kill of mites. So, either mites had built back up in these hives because they were robbing stores from some hive elsewhere which had a lot of mites or the previous treatments had left alive an unacceptably high number of mites.
It is too early to tell whether this treatment has improved my winter losses of bees, but I will certainly use this more widely next year.
In the meantime, those hives that have been lost can be cleaned of dead bees and new bees introduced to repopulate the hives. I have ordered more than 400 packages for my customers to arrive in April and May. Hopefully, with even better mite management, they will fare better in 2017.
Peter Cowin, aka The Bee Whisperer, is President of the Penobscot County Beekeepers Association. His activities include honey production, pollination services, beekeeping lessons, sales of bees and bee equipment and the removal of feral bee hives from homes and other structures. Check out “The Bee Whisperer” on Facebook, firstname.lastname@example.org or 299-6948.