How to Winterize a Beehive
Guest Article by Ruth O’Neill:
Many beehives are lost over the winter, often due to starvation, chilling, pests, or disease. Here are some things you can do to give your overwintering colonies a better chance of survival.
Feed syrup in the fall.
Use a 2:1 mix (two parts granulated sugar dissolved in one part water by volume) and start feeding after the honey supers have been removed, likely in late August. Watch out for robbing, which can be a particular problem in the fall from neighboring hives as well as marauding wasps. Keep the entrance reducer at the smallest opening to help with hive defense. Stop feeding syrup when you wrap the hive (see below).
This blog post talks about how to feed with a liquid, particularly in the springtime, but you feed the same way in the fall.
Leave enough honey in the hive.
Honey bees eat a lot during the winter, particularly in colder regions. For example, in Montana a typical hive eats about 60 to 90 pounds of honey over the winter. Err on the side of leaving too much, rather than risk leaving too little. You’ll have to estimate this visually. For reference, a full shallow super typically holds almost 30 pounds of honey. A medium super holds about 50 pounds. If there is not enough honey in the brood chambers, leave some in an extra super of honey on top. Don’t worry too much about the extra space the bees will have to heat, because if the hive is wrapped with insulation (see next) there shouldn’t be a problem. NOTE: If you do leave an extra box of honey on top of the supers, remove the queen excluder. Otherwise, the queen can’t move up into the top super with her workers, leaving her exposed to the cold.
Wrap your hive.
Although many beekeepers don’t bother with wrapping their hives, even in colder states like Montana, there are several advantages to wrapping. First, the bees will consume less honey if they don’t have to expend a lot of energy staying warm. Second, wrapped hives have warm walls and ceilings, so condensation doesn’t form on them, which keeps the bees drier. Third, warmer clusters are more mobile and have an easier time moving up to access the honey stores. Chronically cold clusters can actually starve to death, even when honey is available, due to their limited movement.
I always wrap hives, but I wait until mid-October when I know there will be no more hot days for the year. Be aware that brief periods of cold weather will not harm the bees, so even if the weather drops down well below freezing before the hives are wrapped the bees will be fine. It is prolonged periods of exposure to cold that wear colonies down and kill them.
Although many beekeepers report good results using tarpaper, I think it has the potential to collect too much heat on the odd warm sunny day in late winter. I prefer to use 1-inch rigid foam sheeting. Sheets of blueboard or pinkboard are available at hardware stores, and these materials offer snug warmth without absorbing too much heat from the sun. Cut panels to fit around the hive, and then screw them together or attach them with bungee cords.
Insulation under the roof is also important to keep condensed water from dripping onto the cluster. You can use many types of insulation such as rigid foam sheeting, quilt batting, scrap wool, packing peanuts, or even newspaper. Typically, it seems to work well to remove the foam core during the last two weeks of March. Obviously, this is weather dependent.
Ventilate the hive.
One of the dangers of inadequate winter ventilation is Nosema, or bee dysentery. It is a fungal disease that thrives in wet and chilly winter hives. Well-ventilated and well-wrapped hives are both snug and sufficiently dry throughout the winter, discouraging Nosema. You need one ventilation gap at the bottom of the hive, and one at the top in order to create good cross-ventilation. In the top of the uppermost brood chamber drill a cluster of two or three 3/8-inch holes. If you haven’t done so already this fall, set the entrance reducer at its smallest opening, which will both allow ventilation and also give the bees access to the outdoors for their winter cleansing flights.
Use the narrowest opening on the entrance reducer.
As soon as late summer hits and nectar sources have largely disappeared, flip your entrance reducer to the smallest opening and leave it there for the winter. It will cut down on problems with nectar robbers, and keep cold fall weather out.
Protect the entrance from mice.
Mice love to invade hives in the late fall, when clustering bees are less able to defend their territory. Some beekeepers use 3/8-inch hardware cloth (sometimes called 21-gauge, “3×3”, or “3-mesh”) stapled over the entrance; you can also drive finishing nails into the entrance reducer opening at 3/8” spacing. This spacing allows bees to come and go, but keeps mice out.
Control Varroa mites.
Every spring beekeepers discover that some of the hives that seemed the most vigorous in the fall have died during the winter because of a runaway problem with Varroa mites. Varroa can flare up quickly in the fall, killing many worker bees. You need to be vigilant at this time of year.
Varroa are at peak numbers in August and September. This is also the time when queens virtually stop producing drone brood, the preferred food source for Varroa during their reproductive phase. With no drone brood around, reproductive female Varroa mites will shift their focus to worker brood cells. This can result in a critical late-season population crash in worker bee numbers as the colony goes into winter.
If necessary, consider using oxalic acid, formic acid, thymol, or another of the products on the market for controlling Varroa mites. Read and follow labels carefully.
Combine weak hives. Hives with critically low worker numbers can be combined in the fall. There are numerous ways to do this, but one of the easiest is to render one of the hives queenless, and then use the newspaper method:
- Move both colonies to a new yard, preferably a couple of miles from the existing location.
- Take a sheet of newspaper and poke approximately 20 slits, smaller than a bee, across the surface.
- In the colony that has a queen: remove the inner and outer covers. Place the newspaper sheet on top of the box.
- Put the queenless colony on top of the newspaper sheet.
- In 2-3 days, the colonies will chew their way through the newspaper and combine into one.
- Here is a video example: https://www.youtube.com/watch?v=voxPI0eTQus
Written by Ruth O’Neill. Ruth is a Research Associate in the Wanner Extension Entomology Lab at Montana State University, who cooperates on a variety of projects related to insect pests of crops. She has experience as a hobbyist beekeeper, and has a special interest in honey bee health and protection.