As noted, my Spring 2017 colony did not survive into Spring 2018. The weekend after discovering my dead colony, I inspected and cleaned out the hive to understand what happened.
The first thing I noticed was that the colony seemed to be frozen in time from when I had last opened the hive 4 weeks prior. The cluster was in the same place – the pollen patties on top were untouched. Something had happened – an event – either during the time I had done my January inspection or immediately after.
I then noticed that the pollen patty I had added in January was really melty on top. And there was quite a bit of mold in the hive.
It was at this point that I had a horrible realization. I had frozen the winter pollen patty prior to winter. I don’t know why. I thought I read somewhere to do this, but I can’t find any proof of that. So most likely, I just thought, “Ew, these winter patties are gross and sticky. If I freeze them they won’t make a mess.” During the January inspection, I put in an extra patty (which probably wasn’t even really needed based on their strong food stores) direct from the freezer.
When I closed the hive, the warmth generated by the colony would have quickly thawed the patty creating a moisture bomb inside the hive. The weak, late winter colony couldn’t handle it and was killed. So, in trying to help make sure my bees had enough food to last the winter, I made a rookie mistake and killed them all.
I cleaned out the hive and sat it out in the sun to dry out (and stop mold growth). My next colony will be able to use the woodenware from my last colony. The bees will easily clean out the mold, and they will have a jumpstart given that I have 2 deep boxes of built out comb with extra honey stores to give them.
Possible Other Causes
I did also rule out other possible causes of death for my colony. First, varroa mites. There were a few mites on the bottom board, but not enough to honestly be concerning. Also given that it happened so suddenly, I don’t believe varroa was the cause.
I was also a little concerned about the possibility of foul brood. It’s not likely, but if the hive was infected with foul brood, I would not be able to reuse the boxes or the frames – they would need to be burned. My main cause for foul brood concern was that there were brood cells with sunken, perforated caps (a sign of foul brood) and when I was removing parts of the comb with brood there was a gross, grey goo.
The good news is that the USDA has a bee research laboratory that offers a free service. You can send them a sample of suspicious comb and they will test it for disease (instructions here). I got the results back quickly – free and clear of foul brood. There’s something very comforting about being certain.
So, I’m pretty confident that the demise of my hive came from that frozen patty. Lesson learned.
New bees should come in late May!