Imagine you have a colony that’s chugging right along. The bees are healthy, you’re getting a good rate of return from foraging, life’s good. Until something starts to change. It’ll happen slowly, at least at first. Maybe a few bees look underweight or are having trouble flying. Pretty soon you notice the hive is producing less swarms. Larvae are dying in their cells. Even if it doesn’t look like much, your colony might be in serious danger. You have a Varroa mite infestation on your hands. These little creeps can spell the end for an otherwise healthy colony, but lucky for us, there are ways of dealing with this threat that can save your bees. First, let’s take a look at what Varroa mites actually are.
Varroa mites are parasitic arachnids that feed on honey bees. They sneak into a hive and start snacking on the fat stores of larvae and pupae, which makes them just about the worst roommates ever. Like in the example from above, early stages of the infestation are hard to spot. Most infestations start small so they can’t do too much damage. The problem comes when they start multiplying. With these kind of critters, population growth happens exponentially, starting slow, but ramping up quick. If left unchecked, a Varroa mite infestation can devastate a hive in as little as 2-3 years. Yikes.
The Varroa mite life cycle happens entirely in the beehive. Except for the first wave of invaders, each Varroa mite will be born in, live in, and die in the hive. An adult female Varroa mite will sneak into a honey bee brood cell before their capped and drop off some eggs. The eggs hatch and feed off the growing bee. When the bee matures, the mites go with them and spread to other cells. Bees fed on like this are smaller and weaker than they’d otherwise be(e). Some won’t make it out of the brood cell, and drones might die before mating. That’s what causes the signs in our imagined colony earlier. Weak bees are poor fliers, and if there’s less mating going on, there’s going to be less swarms. By spreading cell to cell like this, Varroa mites grow in number, and can cause a total colony collapse.
You might wonder why, if Varroa mites are so dangerous, honeybees haven’t worked out a way of dealing with them on their own. After all, if just a couple of Varroa mites can wipe out a colony, how are there any honey bees left? And if Varroa mites needs honey bees to live, what’s the point of destroying the hive? The real stickler is that Varroa mites aren’t a natural parasite to honey bees. Their original hosts are actually Asian honey bees, which have all sorts of natural defenses for them! Varroa mites only came to North America recently. So, don’t worry, you aren’t messing up any kind of natural cycle by getting rid of Varroa mites before they wreck your colony, you’re just helping nature (and your bees) get back on the right track.
Because Varroa mites can be so dangerous, it’s important to know how to identify an infestation as early on as possible. There are a ton of different ways to check your hive for Varroa mites. Each method has its own pros and cons, and it’s important that you find the one that works best for you and your bees. There are some general tips and tricks that can help you spot these diabolical infiltrators before it’s too late.
For one thing, Varroa mites don’t spread through a hive evenly. They clump and grow from their original beachhead. They are also way more likely to target drone broods, which makes sense: their brooding cycle is longer, giving the mites more time to hatch and feed. What all this means, is that you should check multiple sections of the hive. A single brood frame could be totally mite-free, but the sneaky little parasites could be hiding somewhere else. Check at least three frames to make sure you’re getting a good spread.
There’s also the issue of season. If it’s not brood season, then there aren’t going to be any Varroa mites in your brood cells because they’d have nothing to eat. That’s good news because techniques that check the bees for parasites will pick out the mite that are sitting pretty on your buzzing pals. Alcohol washes and sugar shakes are two of the classic ways to check for mites. This also applies vice versa: if you’re concerned about Varroa mites during brood season you’ll have to uncap the cells to look for them.
You should check for Varroa mites regularly, especially if your hive is suffering from some of these symptoms:
Once you’ve figured out that your hive is infected (ugh) the next step is treatment.
There are a lot of interesting studies being done on how to deal with Varroa mites long-term, but when it comes to your hive I’m willing to bet you’d like something a little more immediate than extensive selective breeding. Methods for treating Varroa mites vary. Two common, non-chemical treatments are formic acid and oxalic acid. European and Canadian beekeepers have been using the latter for decades, and it was recently approved by the FDA. You can apply oxalic acid either by vaporizer or dribbling, and both methods impressively reduce Varroa mite numbers. Mites are affected by oxalic acid 70 times more severely than bees, which makes it a relatively safe treatment. Other, natural methods can be used too.
When you’re picking a method, do your research and find out what’s going to be best for you and your bees. Dealing with Varroa mites is a hassle; remember to stay alert, monitor for fishiness, and take action as soon as you can.