BroodMinder Report - April 2020

Have you ever struggled to figure something out only to discover the answer was right there staring you in the face the whole time? That’s the way it has been with the BroodMinder data from our scale hive all winter long.

Starting in December, I have been confidently predicting that by the next month’s report there would be proof that the hive had returned to raising brood. The temperature readings would clearly show that the bees had resumed brooding and were keeping the temps in the lower box in the range of 91-94 degrees F. That fact is one of the most astounding things about honey bee biology. Because these tropical insects are able to maintain those temperatures even if the outside air is more than a hundred degrees lower, as it routinely is here in upstate NY in January and February.

But month after month, the temps above the brood box stayed in the low- to mid- 80 degrees F, too low to indicate there was brood in the hive. I wondered if the sensor was malfunctioning. I considered whether the hive had lost its queen. I called the manufacturer for technical advice.

Finally, in desperation before the March Newsletter went to press, I pried the two boxes apart just enough for me to tug the sensor along the top of the frames to reposition it to where I thought I would have a better shot at seeing the expected “brood zone” temperatures.

And the result was – all evidence pointed to the possibility that I had somehow killed the queen as the temperatures above the lower box plummeted from the steady mid-80-ish range to the mid-30s and 40s, and stayed there.

With nothing but potential operator-created disaster to report, I skipped doing a BroodMinder report in March. After the Newsletter was finished and cued-up to send, I finally had a (barely) warm enough day for a deep inspection. I planned to just find the sensor and move it back to the original position.

As soon as I lifted off the top box, I could see what the problem was. When the sensor was installed last fall, the sensor had inadvertently been laid directly on top of a late season Formic Pro treatment pad. All winter, the temperature readings had been attenuated by the thick, corky substrate of the pad.

With the offending pad removed and the sensor put back in place, I hoped that the temperatures would now begin to show proof of brooding. (And also prove that I hadn’t accidentally killed the queen in my somewhat reckless effort to blindly slide the sensor between the boxes.) When I checked the data on our website that evening, I was hugely relieved to see exactly that. The temperature reading had shot up to 91 degrees F, and has stayed in the “brood zone” ever since.

Lesson learned!

So, the 80-ish degree readings from the sensor had really been indicating low 90s in the brood area all along. Well, as they say, duh! But to end the story there would be to miss the most important point. (Besides it’s best to remove Formic Pro pads when the treatment is over.)

The most important point wasn’t the actual readings, it was the steadiness of the readings. Because temperature readings above a broodless winter cluster can be expected to range quite widely as the cluster expands, contracts, and moves around among different frames to access more honey. But a cluster surrounding brood, once the eggs are laid in those cells, must stay put and keep the temperatures in a very tight 3-degree range in the lower 90s, no matter what.

So, when looking over BroodMinder data in winter, don’t obsess about the raw numbers; look instead for the telltale pattern of steadiness. That’s what lets you know when the bees are caring for brood.