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Beekeeping Through the Winter in the PNW

The winter in the PNW can bee oddly "warm" and wet. When I say warm, I mean in comparison to winter elsewhere in the USA. Below the 57 degrees F honeybees form a cluster in the hive of roughly spherical shape. They keep the innermost parts of their hive at a balmy 93+ degrees F by vibrating their flight muscles. As the outside temperature drops, the cluster tightens.

The weirdness of the PNW weather is that the bees often are fairly loosely clustered and more active, which requires that they consume greater amounts of honey than if they were tightly clustered. That poses the first great overwintering risk to our bees: starvation. An even greater danger comes as Spring draws nearer. The bees begin to produce more and more brood, which puts an even greater demand on their honey stores. As a manager of honeybee colonies, it is important to regularly assess the weight of the honeybee colony to make sure that they have enough stores to make it through winter. If the hive is "light" on stores, emergency sugar feed is required to get them through to the first nectar (and decent weather to forage for it).

Many beekeepers in the PNW regularly talk of how their colonies succumbed to moisture death overwinter and they are not able to keep bees alive through the winter. It is possible that their hive setup allowed for moisture to rain down on the bees and this led to the colony loss (more on that in the next paragraph), but it is far more likely that their bees died of varroa load. My first question is always, "when was your last mite check?" Unchecked varroa loads lead to colony death in winter. This is why it is incredibly important to have varroa under control in the Fall! I treat with Oxalic Acid Vaporization between late November and Early January to knock down as many varroa as possible when they are most likely broodless. This sets them up for healthy early growth in March.

When overwintering colonies, it is important to understand a bit of bee biology while clustering. Bees are made up of cells (like all living things) and animal cells do a thing called cellular respiration to stay alive. They take in oxygen and food to produce energy for life. The byproducts, or waste, of this reaction are carbon dioxide and water. The carbon dioxide sinks to the bottom of the hive and leaves through the entrance - no big deal. The water that is produced leaves their little, wonderful bodies as warm water vapor. The warm, moist air rises (thermodynamics, anyone?) and hits the hive cover. If the hive cover is uninsulated, it is quite cold, and that air cools quickly, forming condensation. If there is enough condensation, it falls as water droplets onto the cluster of bees, ultimately resulting in their inability to keep warm and the colony can die. This is easily remedied by insulating the hive cover allowing the inner cover to warm up a bit which doesn't allow for the formation of condensation.

Wintertime management

  1. Check hive weight - add emergency feed if needed

  2. Clear away the hive entrance regularly of dead bees

  3. Wintertime varroa oxalic acid

  4. Watch the entrance on warm days for activity - if none seen, take a closer look to ensure the colony is still alive.

  5. Prepare equipment for spring growth explosion.

  6. Live for warm weather days and anxiously await SPRING!

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