This month in beekeeping

February and August have historically been the two months on the opposite sides of the nectar flow to treat for varroa mites, but this is not written in stone. There are new mite control options and they have different temperature range requirements and honey super withdrawal times.

In a nutshell, we do not want our varroa mite populations to get too high – 3200 is cited as the economic threshold for the U.S. And we do not want to skip a treatment window if it means that the threshold number will be exceeded before the next treatment window.
The need to treat should be based on your current mite population. If you have a high mite population, you should treat immediately. If it was today (February 11th) your options would be Apistan and Checkmite. If you have a low mite population, you can delay and treat in March or April with controls that require shorter withdrawal times before supering but higher daily high temperatures for use. Mite Away II can be used between 50-79 degrees F and Apiguard between 60-105 degrees F.
Our most efficacious mite controls buys you about 4 months which includes the treatment period before you need to treat again. It should be noted that this period can be extended by using mite tolerant stock, screen bottom boards, drone brood removal, powder sugar, etc.
I think one possible and viable treatment option for Oregon beekeepers is to use Mite Away II in the spring (March/April) and Apiguard in August. Hopefully, before next winter oxalic acid will be registered for use during winter broodless periods.
How do you estimate how many mites you have? I will explain two techniques: the alcohol wash and the natural drop count.
An alcohol wash can be used to estimate varroa populations with or without the presence of brood. It is simply a ratio of the number of mites per given number of bees multiplied by the total estimated bee population, and then factoring in the varroa population hidden in the brood. It is estimated that 2/3 of the mites are within the brood itself. An example: brood is present, and there are 30,000 adult bees. You find 5 mites in a ¼ cup alcohol wash (about 150 bees). This is equivalent to one mite per 30 bees, or 1000 mites total on the adult bee population. Add the 2/3 hidden in the brood, and you have roughly 3000 mites, which is close to the economic threshold number of 3200.
The natural drop estimate for varroa population requires full cycles of brood. Incidentally, these numbers for both techniques come from Dave VanderDussen – the Mite Away II proprietor. It is best to do a three day, 24 hour sticky board drop count. Each fallen mite represents 1% of the total mite load. This means you multiply the average drop count by 100. An average drop count of 32 mites in 24 hours would equal 3200 total mites, or the economic treatment threshold.
Other tasks aside from worrying about varroa mites…
Heft hives to find any light ones. Provide light hives emergency feed, preferably sugar candy/fondant or frames of honey. This is prime time for starvation, as brood production increases energy demands. When daytime highs exceed 55 degrees, fumagillin medicated syrup can be used instead of fondant or frames of honey.
Feed all colonies Terramycin in powdered sugar weekly for three weeks to prevent American and European foulbrood. Terramycin requires a 4 week withdrawal time between the last antibiotic treatment and the first marketable nectar flow. Tylosin provides up to 4 weeks of protection with a single treatment, but there is a caveat: it is more persistent and requires an even longer rest period than Terramycin before supering. There is a growing problem with Tylosin being detected in honey in the U.S.
Look for signs of Nosema infected hives. Symptoms include: slow build-up (best indicator), disjointed wings, distended bloated abdomen, a lot of yellow streaks on the outside of the colony and crawling bees outside of the hive. These symptoms may also be associated with tracheal mites. Make sure suspect hives have good ventilation and treat with fumagillin syrup (follow the directions exactly, overdosing does not help, and treat fumagillin with respect as it is dangerous stuff).
Find and remove queenless or dead out colonies. If pollen is actively being brought in, this generally indicates a healthy queen and hive.
Remove dead outs and find out why it succumbed – queenlessness, starvation, disease? If the equipment is disease free and in good shape (frames are not all dark, with thick cell walls, riddled with drone brood cells), store for future use in dry location stacked on end so air and light can penetrate to discourage mold growth and wax moth activity.
Spring usually brings some of the wildest and windiest weather – albeit we have already had tremendous winds this winter. Make sure the lids are secured after you break the seals.
If you feel your area lacks sufficient natural nectar flows and pollen to fuel high-energy growth to make full-sized production colonies in time for the main nectar flow (end of May), feed fumagillin medicated sugar syrup and pollen substitute when the daily highs exceed 55 degrees.
Wax moth activity dramatically picks up when the temperatures rise. Keep an extra eye out for stored frames that have had brood and have pollen. Moth crystals (paradichlorobenzene) can be used for control, as well as freezing the frames. Exposing the frames to light can inhibit the moths, too.
Here’s one last thought: Don’t feed pollen substitutes too early. I would consider too early as January, February, and maybe the first part of March. Brood production will increase, which may exhaust winter food supplies prematurely. It also increases activity, metabolism, and hive moisture. The weather may be inappropriate for cleansing flights, increasing the likelihood of developing dysentery. Dysentery is the quickest and most effective way of converting a slight nosema infection into a severe one. Winter should be a time of quiescence for the bees that enables the bees to live to take the colony over the period when little or no brood is being reared. My two cents worth.