September 2018 Beekeeper’s Corner

By Gerald Przybylski

Jerry has been an East-Oakland beekeeper since 2011; local bees preferred.

It’s time for us ACBA member beekeepers to do something in the service of fellow beekeepers across the country.
I’m entering Varroa percentage data at the Mite-A-Thon website, and so should you.
The Mite-A-Thon website is open for input September 8-15 for Varroa percentages in all our hives. Our data is aggregated with data from everyone else. Collectively we take a snapshot of the Varroa problem across the country. 
We get to see where we stand.  If we’re reading the results, it’s only fair that we provide our data too
Don’t worry… you don’t have to give away your address if you’re a stealth urban beekeeper.
It’s a good reason to inspect the hives too. Make the most of it.
But, you say, “I don’t know how to do a sugar-roll…”
Well… here is what I do:
* Collect equipment:
– Bin to shake bees into;
– A half cup measure (on a stick);
– A container to roll bees in, and a screen cover (commonly a wide-mouth canning jar with #8 screen in the ring)
– A white inspection surface like a large plastic plate or bucket lid.
– A spray bottle with water for spraying the sample plate, and cleaning up.
* shake the bees off of a brood frame into a bin (MAKE SURE THE QUEEN IS NOT ON THE FRAME)
* Leave the bees in the bin undisturbed for a minute or two; field bees  will fly back to the hive.  <DON’T SKIP THIS STEP!>
* Scoop a half-cup of bees from bin into the container; add a about 2 tbsp. of powder sugar, and cover.
* Gently roll and tumble the container for about 45 seconds. (aim for the same length    of time every time)
* let the covered container rest  in the shade   for 3 minutes. <DON’T SKIP THIS STEP!> During this rest time, the bees buzz and flap and raise their temperature.  Varroa don’t like heat, so they crawl out from their place between abdominal plates and get coated with powder sugar.
The delay step improves the efficiency of the Varroa shakeout .
* Shake powder sugar and Varroa through the screen onto a white surface for about 45 seconds.
* Spray water on the powder sugar. Count the Varroa. They’re dark reddish brown and the size of the head of a pin.
* Divide the Varroa count by 300 (roughly the number of bees in a half-cup measure) and again by 100 to convert to “percentage”
“Should I worry about accuracy?” one might ask…
Accuracy translates to confidence in stating the value reported.
The value we report is a fraction converted to a percentage. The numerator and denominator have errors.
The limit of fractional error in the Varroa percentage is the sum of the fractional error in the number of Varroa plus the fractional error in the number of bees in a half-cup.
But… there is zero error in the number of Varroa counted, right?    It is only true if sampling the whole hive.
When taking a small sample of a large population (1/2 cup of bees in gallon of bees),  the number of Varroa per sample varies. Successive samplings of the same hive will extract different numbers of Varroa.  With doing random sampling, the error is roughly the square root of the number of Varroa counted in the sample.
(It’s statistics theory, and demonstrable in your hive if you do many samplings of the same hive)
Likewise, the number of bees in a half-cup is never exactly 300 either.  The square root of 300 is ~17, which we can use as a very rough estimate of the variability/error.
Lets work through the example of 9 Varroa in a half-cup of bees.
Applying the error analysis, the fractional error in the number of Varroa is (√9/9 + √300/300) = ( 0.333 + .058) = 0.39 or 39% of the calculated value of 3%.
So we report a 3% ± 1.2% Varroa.   (the 1.2% comes from 0.39 x 3%)
For 1 Varroa in a half-cup of bees, we report 0.33% ± 0.35%…  Yup, the error is comparable to the value!!
For 36 Varroa in a half-cup of bees, we report 12% ± 2.7%… implying a pretty reliable measurement.
We’re deep in Robbing season. Bees happily cope with entrances that are one to three inches wide. A narrow entrance greatly eases the work of the guard bees keeping intruders and robbers out. As long as they have sufficient airflow the bees maintain control the climate in the hive.  How to tell? If bees beard a lot, they’re circulation challenged.
Improve air circulation with migratory (solid) bottom boards by narrowing the entrance with screen instead of a stick or “entrance reducer.”
With screen bottom boards (with unimpeded air flow below the screen), use either sticks or screen to narrow the entrance.  Narrow entrances also improve colony sociability.
Check hive weight every week or so. Colonies with some capped honey, even if it’s all on brood frames, are still have enough for now. Colonies with some beebread stored near brood frames have enough for now.  Offer syrup to fall swarms and cutouts.
Keepers of a single hive risk being bee-less next February as long as 25 to 40% winter losses continue. As insurance, consider keeping a second colony or a nucleus colony as well.  If planning to expand next year, it’s time to think about acquiring and assembling additional equipment, planning for splitting, and/or identifying the sources of additional colonies, nucs or queens between now and March.  Consider procuring bees and queens only from sources within the county who breed local bees.
It’s time to start cleaning up equipment pulled from hives after this year’s honey flow. Save propolis scrapings; you can use them to make a wash/varnish that can be painted on the inside of boxes. (propolis dissolves in alcohol)
Replace/repair broken equipment. Renew the foundation in smelly black brood frames