Varroa Mite Treatment for Bees

Don’t despair over your dead colony. Instead, identify the problem and find preventative solutions to keep the rest of your hives healthy.

Reader Contribution by Julia Miller
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by Adobestock/Vadim

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Dead-outs: that dreaded event in a beekeeper’s world when an entire colony of bees dies in the hive.

It was a heartbreaking day in mid-December when we found that one of our colonies had died out. Every few weeks throughout winter, a day rolls around that’s warm enough (50 degrees Fahrenheit) to check the hives. Typically, we add candy boards during these checks as a supplemental food supply. Two of the three colonies were thriving, but the third contained only dead bees.

After taking a moment to apologize to the queen and feel sorry for ourselves and the bees, I decided to learn from this unfortunate experience.

Causes of Dead-Out Hives

It seems dead-out hives are a winter malady. They can be related to the cold weather or evidence of a weak colony. The best way to find out is to take the entire hive somewhere and complete a thorough post-mortem examination. Here are some things to look for.

Varroa mites or tracheal mites. Look for bees with deformed wings. K-shaped wing deformities may indicate tracheal mites. Pick through the layers of debris on the bottom board and watch for signs of Varroa mites.

Small hive beetles and wax moths. Small hive beetles are little, black, hard-shelled beetles that take up residence in the crevices of the hive. Cottony, oval-shaped cocoons or oval-shaped depressions on frames are signs of wax moths. An abundance of either is evidence of a weak colony; strong colonies of honeybees are hygienic and will keep these pests in control.

Starvation. As you examine the frames, note the position of the dead bees. Are they stuck headfirst in cells? Is the cluster mainly located a frame or so away from a supply of honey? Both conditions indicate starvation. If it becomes too cold for the bees to reach their food supply or they didn’t have adequate stores to get through winter, they’ll starve.

Other causes. There are other potential causes for a dead-out, such as a weak queen, foulbrood, or even a rodent infestation. Observe your dead colony for indicators of these conditions.

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Now What?

After you’ve identified a potential cause for the loss of the colony, there’s hope to save the rest of your apiary. For example, starvation can be counteracted with supplemental feedings or leaving more honey stores in fall. The condition you find will steer you to the correct solution. After a dead-out, clean all boxes and frames thoroughly. If you’ve discovered foulbrood, all equipment and dead bees must be burned to prevent spread.

If you find signs of small hive beetles or Varroa mites – two of the most primary pests in honeybee hives – it’s imperative to contain them early, especially in the establishment of a new hive. Both pests can weaken a colony if allowed to infiltrate.

The following methods aren’t perfect and won’t rid your hives entirely of Varroa mites and small hive beetles. But with a bit of due diligence, you can keep their populations at a level that a strong colony of honeybees can manage.

Varroa Mite Treatment

Closeup of a hive tool pointing to a small red Varroa mite in a

Varroa mites are small, round, red-brown pests that can appear in your hive. They normally feed and reproduce on honeybee larvae and pupae, though they can also feed on adult bees. Their presence can weaken a hive and may even transmit viruses.

We prefer to use natural methods to treat for pests whenever possible. Since we’re a hobby-level beekeeping operation, these methods are an easier option than if we were attempting to run a commercial apiary. Although, several chemical treatments that have been deemed safe for use with honeybees do exist on the market.

Powdered Sugar Dusting

A sieve filled with powdered sugar shakes above beehive frames,

Dust a half-cup or so of powdered sugar over the bees. A simple fine-mesh sieve is the only tool required. Powdered sugar contains a small amount of cornstarch, but it’s not enough to harm the bees. This dusting will address mites feeding on adult bees in two ways. First, it’ll encourage the bees to clean themselves, essentially grooming off the mites as they do (think lice comb). Second, the powdered sugar will coat the mites, and they won’t be able to hold on to the bees.

Screen Bottom Board

Replace the solid bottom board of the hive with a screened version. When mites are dislodged from the bees, they’ll fall through the floor of the hive. Varroa mites aren’t good climbers and will be unable to climb back up through the hive to find another host.

Drone Comb

“Drone comb” is exactly what it sounds like: honeycomb that’s sized for drones. When a queen approaches an empty cell, she first measures the cell with her front legs. The depth of the cell signals her to lay the type of egg needed. The deeper drone cells prompt her to lay an unfertilized egg. Varroa mites are attracted to drone cells, because their eggs take longer to incubate, so the mites can lay more eggs.

Once the drone cells are capped, pull out the drone frames, freeze them for 24 hours to kill the larvae and mites, and then scratch open the cells. Replace the opened cells in the hives, where the bees will clean them out and start the cycle over again. Using the drone comb works with the natural cycles of both bees and mites, so it’ll interrupt the Varroa mite’s life cycle.

Drone comb is typically green in color, so it’s easy to find in the hive. Most beekeepers who use this technique place a frame of drone comb in the outer positions in the brood boxes. This placement encourages the mites to gather away from the worker bee cells, in addition to providing a system to remove them.

Handling Small Hive Beetles

Small hive beetles seek out honey and beehives, and, once they’re inside a hive, they nestle in small cracks, edges, and corners. You may see them scurry under frame spacers or into spaces between boards.

A healthy colony will sequester a small population of beetles and keep them in check. They’ll often post guard bees near the beetles’ hideout to keep them contained. Some beekeepers have even noted something of a propolis cage the bees constructed to keep the beetles in one area. However, if the population gets out of control – in a weak hive, for example – the beetles can take over, contributing to a die-out of that colony.

Piece of hive covered in bees and small hive beetle larvae.

When the small hive beetle population gains strength, they’ll leave the crevices and move into the comb. The larvae will feed on honey and the honeybee pupae. A yeast that’s carried by the small hive beetle will cause honey to ferment and create a slime in the honeycomb, which will ruin the honey. Therefore, be mindful of the small hive beetle population, and take steps to reduce or eliminate beetles in the hives.

Beetle Traps

There are several styles of traps, all of which use an odorless oil, such as vegetable oil, to drown the beetles. An attractant, such as apple cider vinegar, can also be added to lure the beetles to the trap.

Disposable traps are small and usually sit between the frames, while most reusable traps are placed along the outside edges of the frames. Once reusable traps are filled with beetles, take them out, dump them, and refill them with oil. When removing them, take care to ensure you don’t spill oil in the hive or on your bees.

You can also use a type of trap on the hive’s bottom board. Place a spacer on the bottom board, followed by a tray filled with oil. It has a screen bottom board with a tray that allows the beetles to fall into the oil but prevents the bees from falling through. Check and empty this trap every week or so until the infestation has diminished. This style of trap is most effective from late spring to fall, when beetles are most active.

2 Pests with 1 Product

For treating Varroa mites, our state bee inspector advised using Mite Away Quick Strips, which will also help suppress the small hive beetles. While using powdered sugar may be effective for mites, it won’t have the same effect in diminishing hive beetles. The active ingredient in Mite Away Quick Strips is formic acid; it’s approved for use in organic hives and during the honey flow. This may be an effective option if you suspect your hive is suffering from both mites and beetles.

Smashing Beetles

Whenever you’re in the hive and see a beetle, be sure to smash it with your hive tool. It’s a small effort, but each beetle smashed is one less beetle in the hive.

I won’t let a dead-out deter me from keeping honeybees – and you shouldn’t, either! Strive to learn from your experiences, and you’ll become an even better beekeeper.

Julia Miller is co-owner, farmer, and beekeeper at Five Feline Farm. She’s also the author of Simply Delicious and The Long Road To Market. Connect with Julia on Facebook, Twitter, and Instagram @FiveFelineFarm.