By Gerald Przybylski
Jerry has been an East-Oakland beekeeper since 2011; local bees preferred.
The Varroa are coming…
We all know and accept that all of our hives have some Varroa mites in them. They spread around by hopping from bee to flower to bee or by hitchhiking on bees and drones that drift between hives.
Many of us who have been periodically assessing the Varroa population in our hives notice that the percentage infestation hasn’t been anything to worry about all through the spring.
That’s odd, isn’t it? The books tell us that Varroa numbers will build up (exponentially actually) in our hives because our bees have no resistance to them.
Doesn’t the evidence of consistently low levels of infestation, perhaps below a threshold, say that our bees must be keeping them in check by grooming, ankle-biting, expression of the hygienic trait, and the by expression of any other mite-resistant traits?
So everything is OK… right?? NO!! It isn’t…
When the summer dearth kicks in (the shut-down of nectar and pollen foraging), our bees get stressed and desperate.
Desperate bees discover robbing. The hives that are easy to rob are the weak, often heavily Varroa-infested ones! They may be managed hives or unmanaged hives or feral colonies in bee trees, attics, walls, crawl-spaces, abandoned water heaters, etc. No control by anyone.
Varroa hop aboard robber bees, and hitchhike back to our healthy colonies. A robber bee can carry as many as ten Varroa back with her!
The Varroa then hop onto house bees in our hives, infest brood, and increase their population at a rate our colonies are no longer capable of coping with. Bee brood numbers, and health take a hit. Viruses get spread around. Stressors increase. Infestation rates spike.
A month or two later our colony dies due to Parasitic Mite Syndrome or some related problem.
So… what do we do?
We ask ourselves why our hives rob. We presume the signals in the hive tell them to.
Empty space is a strong signal to fill up that space with nectar or honey.
We usually have plenty of empty space in our strongest hives because we want the bees to fill it up with honey to harvest!
So perhaps the problem is us and our management practices…
The Seeley paper
hints that single-box colonies have better survival success than multi-box hives.
Perhaps well-provisioned, healthy single-box hives don’t rob, so don’t bring back hitchhiker mites like the robbers do.
No robbers, no spike in mite population.
The books tell us that interrupting the honeybee brood cycle interrupts the Varroa reproduction cycle.
Caging the queen and splitting can be used to introduce a brood-break.
Splitting turns a large robbing-prone hive into two or more small ones that are less inclined to rob.
The books also tell us that drone trapping/culling eliminates Varroa reproduction in the drone brood where Varroa reproductive success is two or three times higher than in worker brood. Drone culling can be done with “Drone-Frames” or with a “capping fork.”
The bible of treating for (acaracide) Varroa Treatment is
found at http://honeybeehealthcoalition.org/varroa/
The booklet has the best description of how to do a “sugar-roll” to measure the Varroa infestation percentage in a hive.
Roll the bottle to distribute the sugar… always for the same time for consistent results.
ALWAYS let the jar stand in the shade for three minutes. (The sugar-covered bees get annoyed and vibrate to shake off the powder. Shaking increases their body temperature. The temperature rise causes the Varroa to detach from the bees!! Wait for the temperature rise.)
Then shake the mites out through the screen onto a white surface. Spray the sugar with water and count.
The HBHC guide contains a table of “listed” Varroa control chemicals, including the ones that don’t work any more. The most common ones still used are Thyme oil, Formic acid, and Amatraz. Apply according to the instructions provided by the manufacturer.
At http://beesource.com/ and at Randy Oliver’s website http://scientificbeekeeping.com/ you can find descriptions of the use of Oxalic acid to kill phoretic Varroa. You can find recipes for dribbles. You can buy heaters for vaporizing the oxalic acid crystals.
The most innovative new time-release delivery method involves the impregnation of a paper or cardboard material with a solution containing glycerin and oxalic acid. See http://scientificbeekeeping.com/oxalic-shop-towel-updates/
Oxalic acid isn’t “listed” as an approved mite treatment. Randy has approval from agencies to conduct his experiments.
This organization doesn’t approve of anyone breaking the law.
There is evidence in our very neighborhoods that the bees are keeping Varroa in check. Bee trees survive from year to year without any treatment being applied to them. The same is true for colonies in attics, walls, crawl spaces, abandoned water heaters, etc. The colony in the 5-foot tall plastic T-Rex in our back yard hasn’t died out since we got it two-and-a-half years ago. We’ve lost roughly the national average of colonies in the same time period. There’s a message there.
When all the surviving colonies control their Varroa we won’t have the “mite-bombs” that wipe out our colonies. The simplest (perhaps simplistic) way to get to all Varroa tolerant/resistant colonies is to stop treating for Varroa. Susceptible colonies die out. Resistant colonies survive. Nature has been doing that exact management practice with feral bees since 1988 with progressively more success.
In our yards it’s more complicated. Some of us only collect swarms that we hope are from resistant/tolerant feral stock. Sadly many of those colonies die, often from Varroa explosions.
Why are the feral colonies surviving year to year when the colonies of feral origin in our hives are not? The big difference is that we beekeepers manage the colonies in our yards. The feral colonies manage themselves.
So… management-wise, what are we doing wrong? Before Varroa we managed our hives any way we liked without impacting survival. Now our management practices have impacts.