Let me begin by saying that a truly complete guide to treating bees for Varroa mites would probably read like a thesis. How many of us can’t wait to curl up with a good thesis? No hands. That’s what I thought.
This guide will provide you with a condensed version of Varroa mite treatment options for the hobbyist or small-scale beekeeper.
We are yet to understand our nemesis completely. Scientists are doing as much as they can to creep into their secret lair and find out their secrets.
Varroa mites don’t play fair, though. Their superpower is their ability to adapt to our weapons.
So let’s begin by identifying what these creatures are.
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Where do Varroa Mites Come From?
Short answer: The Varroa mite (Varroa destructor) came from the underworld where all Batman villains dwell. Well, it’s the short answer, but it’s not exactly accurate.
Mites were discovered in the U.S. in the late ’80s. Since then, it’s been doom and gloom in the bee kingdom.
As you may know, honey bees aren’t native to our great states. All the bees living here today are mostly descendants of European bees and, recently, some Australian bees.
The Asian honey bee coexisted with the Varroa mites without suffering the same fate as their cousins in the West.
It appeared that these Asian honey bees were Varroa mite-resistant bees. If this were varroa ground zero, that would explain the devastating effects it has had on bees in other regions. The honey bee colonies would have had millennia to evolve mite resistance against Varroa mite infestations.
On the other hand, the European honey bees, being late to the game, were caught defenseless when the invasion of Varroa mite populations happened.
What we know now is that the mite population has spread across the country. All beekeepers have a responsibility to do their part in fighting this menace.
There are some bees, like the Saskatraz, that have a higher tolerance to Varroa mites. But that’s a story for another time.
How Do Varroa Mites Spread?
Just like bad news, Varroa mite populations spread like wildfire. These mites spread through worker bees, robbing bees, and drone bees. The main aim of the Varroa mite is to feed on the pupating bee brood.
Spreading Through Worker Bees
Whenever Varroa mites are hitching a ride on unsuspecting worker bees, that’s their ultimate destination.
Recently, they have been found to snack on the fat reserves of adult bees, which we will go into later.
They are happy to hitch a ride wherever they find it. If they find themselves dislodged from one host on a flower, they’ll hop onto another worker from a different honey bee colony who comes to forage.
Spreading Through Robbing Bees
They also spread through robbers.
As if robbing a weaker colony of their hard-earned honey wasn’t enough, these robbers bear very nasty tidings in the form of the mites that they leave behind.
Spreading Through Drone Bees
Another way that the mites get around is by riding on drones. Drones are the perfect cab.
Unlike worker bees that are loyal to their colony, drones will stop by any hive as long as they’ll have them.
What do Varroa Mites do to Bees?
This hitchhiking behavior is known as phoretic behavior. But unlike many other mites that are simply looking for a lift, Varroa Mites feed on the hemolymph as well as the fat bodies found on the abdomen of adult bees, which is the equivalent of blood for the bees.
If you look up a picture of varroa mites, you’ll notice they look like ticks. And like their parasitic cousins, they weaken their hosts. In addition, they even infect them with honey bee viruses such as the Deformed Wing Virus (DWV).
Bees depend on their wings for survival. When honey bees are infected with this virus, particularly at the pupa stage, they end up flightless and weak. This, along with other honey bee viruses, can result in a condition known as Parasitic Mite Syndrome (PMS) and can lead to poor health, even death, in the honey bee population.
Hitchhiking on a bee makes it difficult to prevent mite entry into the hive.
And as you can imagine, this has a significant impact on the honey bees, who will most likely die from the Varroa mites.
The beekeeper is then left with two options; monitoring and treatment.
When to Treat Your Bees for Varroa Mites
For any Varroa mite treatment to be truly effective, it must be able to reach the mites. For that reason, the effective treatment for controlling Varroa mites is timed when the capped brood is minimal or absent altogether.
You also need to understand when the Varroa mite is most vulnerable. Once you do that, then you’ll time your treatments for maximum effect.
The first step is to know your enemy. To kill the Varroa mite, you must be the mite. Well, maybe not, but you do need to understand the life cycle of the mite.
Just like fleas, the Varroa mites that are roaming about on adult workers are usually the minority. Most of the Varroa mite population is hidden in capped brood cells, where they remain fairly safe from most of the compounds used to kill them.
When is This?
Fortunately, this part is easy to predict once you gain some experience.
Honey bees are pretty economical insects. If they were people, they would have an excellent credit score.
Left to their own devices, honey bees will not raise more mouths than they have the resources to feed.
When they anticipate that there will be a source of nectar, they prepare by building up the numbers and building a comb so that the queen bee has multiple cells to lay eggs in.
Once the nectar season has passed, queen bees tend to slow down on their laying activities, and the numbers of broods drop gradually until the bees are ready for winter, during which time the queen probably won’t lay any eggs.
When You Should NOT Treat for Varroa
Treating Varroa mite infestation in the winter is not recommended for two reasons.
One, if the colony was heavily infested with mites before, you could wind up with a colony heavily infected with DWV.
Since your treatment options only kill the mites, your infected bees have a weakened immune system, and the colony is likely to die anyway.
Two, depending on where you live, the winter temperatures may get too low for some of the treatments for Varroa mites to be effective.
In the winter, bees cluster together to keep warm, so the last thing they need is you ripping the roof over their heads, letting the cold air in.
With that in mind, you want to manage Varroa mites before the onset of winter when there is little to no brood. It is also recommended that the supers be removed prior to mite treatments to avoid contaminating your honey.
Is There Really a Best Time to Treat for Varroa Mites?
Well, that’s a subjective question. There are several schools of thought, and I guarantee that each one has a strong defense from the beekeeper practicing it.
You need to find a solution that’s healthy for the bees, kills the mite populations, and doesn’t cause you, the beekeeper, much harm.
Some beekeepers undertake Varroa mite control and treatment once a year, at the end of summer or early fall, and it’s enough.
I like that idea because multiple Varroa mite treatments within the year do not sound healthy for the honey bees or the handlers, for that matter.
The treatment options that we shall explore below try and balance the health of the bees while eradicating as many mites as possible.
It’s important to note that due to irresponsible treatments, the mites we have today are immune to many commercial pesticides that have been used to treat them.
They’ve become like superbugs. Imagine if you kept self-medicating every time you got sick. Eventually, you would breed a bacteria in you that is completely unaffected by your general antibiotics and could eventually kill you.
The Varroa destructor mites have made treatment rotation as essential as the treatment itself.
When dealing with organic acids, for example, you can use Oxalic acid this year and then formic acid for the next Varroa mite treatment.
Although resistance to these compounds hasn’t been proven, their effectiveness reduces if only one compound is used in consecutive treatment sessions. So, it’s best to get acquainted with as many options as possible because you’ll probably need to try most, if not all, at one time or another!
Before we get into the treatment options, first, you need to monitor your mite count, which will allow you to get a better understanding of the Varroa mite numbers you’re dealing with.
How to Monitor Your Mite Count (With a Screened Bottom Board and Varroa Drawers)
Treating honey bees for Varroa mites entails monitoring and counting.
Monitoring your mite population involves using a screened bottom board like this one here, which is a mesh that replaces the solid ‘floor’ of the hive.
This means that any Varroa mite that gets dislodged from the bees falls right through the floor and out of the hive. By then, they are at the mercy of nature and end up as a buffet option for another creature.
To confirm the presence of Varroa, you can add a Varroa drawer under the screen. This is a sticky board that traps the Varroa that gets dislodged.
Once the mites land on the board, they can’t get back to the hive because they get glued to the board. Taking out the drawers is quite simple and not invasive.
Once you look through the debris on the board and confirm a Varroa infestation, you may need to do a mite count.
What is a Varroa Mite count? Think of it as a survey. You aim to come up with an idea of the mite-to-bee ratio.
How to Do a Varroa Mite Count
To do this, you need a jar with alcohol, a measuring cup, and some nurse honey bees. Nurse bees are preferable because their proximity to the brood makes them the best hosts for the majority of the Varroa mite population.
Therefore, this only works if you get a frame of honey bee brood from the brood box and scoop up about half a cup of nurse bees.
They don’t fly away, so if you shake off the bees into a container, the foragers are likely to take flight, and those that remain at the bottom are likely to be nurse bees.
You then scoop up half a cup with your measuring container. Half a cup contains about 300 adult honey bees, and that is used to determine the ratio.
The adult bees are then put in the jar of alcohol and given a good shake for a few seconds. This kills both bees and mites, but it is very effective in dislodging the mites from the bees.
You then run this mix through a sieve to separate the bees from the alcohol and mites. The mites will sink to the bottom of the liquid, and you will be able to count them quite easily.
With the number of mites known and an estimation of 300 bees in the sample, you can get a percentage of Varroa infestation and decide whether to undertake Varroa mite treatment or not.
Once again, the acceptable threshold for mite control and treatment is subjective. Some will do so at 2%, so it is up to you.
One of the reasons why one would start controlling varroa mites and treat them when the number seems so low is you need to consider that most mites could be safely behind the wax seal of a pupating bee.
So, you’ll want to begin your Varroa mite treatment because mites will continue to emerge as the cocooned bees break out of their cell, meaning the mite count will continue to rise.
If you decide to treat, which you should, let’s explore some ways you can treat your bees for Varroa.
How to Treat Varroa Mite Infestations
There are two primary ways that you can treat Varroa mites; through the use of organic compounds and undertaking other control methods such as splits and a sugar shake.
Below we discuss the best organic way for treating honey bees for Varroa mites. Then we transition into discussing other control methods that you can use to treat Varroa mite infestations.
Yes, the organic craze is with the beekeepers now, and with good reason. If it’s organic, then it’s likely to be found in nature, which minimizes the health risks to us and other organisms.
In the case of organic acids, there are three that help control Varroa mites in honey bee colonies. Formic Acid, Oxalic Acid, and Beta Acid help control Varroa mite populations.
Treating honey bees for Varroa mites may be done with the use of Formic Acid. This one is a favorite of many because, unlike the other organic acids, this one penetrates the wax that seals the pupating brood in the cell and manages to kill the varroa feasting on baby bee blood.
Honey already contains trace amounts of formic acid and is, therefore, unlikely to contaminate the honey in the hive. Even so, it’s always advisable to carry out treatments once you have removed your honey supers from the hive.
How to Handle and Use Formic Acid for Treating Varroa Mites
Being an acid, you have to be careful in handling this. And as a beekeeper, you’ll need to take some safety precautions before you begin handling this compound.
First of all, make sure you’re wearing gloves like these to prevent any contact with your skin.
Second, ensure you have a good amount of water near you just in case some of it spills or splashes on you.
Third, it may be prudent to get a gas mask because the formic acid acts by evaporation, and if you’re working in a poorly ventilated room, you could find yourself spattering and coughing.
Let’s not think about what acid does to the lungs, but since I mentioned it, I’m sure you can appreciate the need to be cautious.
Formic acid is usually applied using strips that are placed on the top bars and draped across several frames. The formic acid then evaporates in the hive and spreads to control mites.
In addition to that, your honey bees, in an effort to keep a tidy home, may try to dispose of the strips. This means that they will be rubbing against the strips and getting some of that acid on their little exoskeletons, spreading it across the hive as they bump into each other.
If you choose to drape it across one frame and the strip covers part of the comb, there’s no problem. The queen bee will continue to lay her eggs on the cells around the strip.
The downside to formic acid is that it requires relatively warm temperatures, with the ideal being around 30° Celcius, which is 86°F. It is important to read the instructions before you administer this treatment.
This is the McGyver of the group. Oxalic acid is used as wood bleach but happens to be deadly to Varroa. It exists naturally in some flowering plants and vegetables, such as spinach and rhubarb.
When administered responsibly, it does not cause any distress to the honey bees, though increased mortality can be seen if you use this product too often.
How to Use Oxalic Acid for Treating Varroa Mites
Oxalic acid can be administered in two ways: vaporization and dribble. Both methods have their pros and cons.
Oxalic Acid Vaporization
Vaporization is very effective as the acid is vaporized, and the crystals spread all over the hive and on the bees. It does not depend on bee-to-bee contact to spread.
The downside is you will need additional equipment in the form of oxalic acid vaporizers and a proper gas mask.
Oxalic acid vaporizers turn oxalic acid crystals into vapor. As the vapor condenses, it forms fine crystals that cover the interior surfaces of the bee hive.
Vaporized oxalic acid is extremely dangerous when inhaled, so standing upwind of the vapor is not enough as a precaution.
The dribble method is simple to administer. Dissolve the acid in sugar syrup and then drizzle directly onto the bees.
The tricky bit is that the dosage per honey bee hive is quite small. For equal distribution, you will need to measure how many milliliters you will drizzle per seam (the space between two frames). If you put too little, it will be ineffective.
If you put too much, you could harm the bees. Or you will wind up with a very soggy hive that can bring about other complications.
That said, with a little experience, you will get better at it, and some tools can help you measure the exact amount needed per frame.
Downfalls of Using Oxalic Acid
Unfortunately, Oxalic acid does not penetrate cell caps, and therefore, the mites feeding on the pupating brood remain unscathed. This is why this treatment is best used when there is little or no brood present in the hive.
Recommendations for using Oxalic Acid
Ensure that you do not exceed the dose per hive. If you are using the dribble method, you need to make sure that the liquid lands on the bees as opposed to the top bars.
Since bees are in constant motion within the hive and always wind up rubbing against each other, the acid will spread through this contact. This contact will expose as many phoretic mites to the acid as possible.
Hop Beta Acids
Just when you thought the beer had given all it had to offer, you get a mite killer from the main ingredient, hops. The hop plant produces the acid in this treatment.
It’s a weak acid known to deter some sap-sucking pests like aphids. From most accounts, it’s quite easy to use, albeit a little messy.
All you need is to drape soaked strips across a brood frame such that most of the strip is in direct contact with the comb.
As the bees rub against it, even chewing it to remove it from the hive, the solution spreads throughout the hive. This movement kills the phoretic mites.
Disadvantages of Hop Beta Acids
Unfortunately, just like oxalic acid, it cannot affect mites nestled in sealed brood cells.
Another disadvantage is that the strips dry out quite quickly. And so, you may need to wet them three times in the same week.
Even so, it is a very effective treatment with very little effect on bee health.
Nature comes through once again in the form of essential oils. In this particular case, our gift-giver is the herb thyme.
Of all the essential oils tested, this one has shown the greatest results in killing mites.
Also, getting a mite treatment gel like this with Thymol as the active ingredient is a natural, non-toxic treatment for varroa mites, tracheal mites, and chalkbrood.
Thymol works by evaporation in the hive, making it extremely sensitive to temperature. If it’s too cold, no vapors equal no mite deaths.
If it’s too hot, the vapors could kill the bees. That sweet spot is between 60°F and 90°F.
This would place the ideal time to treat at the end of summer or early fall. August fits the bill perfectly. By then, any supers that were full of honey would have been harvested.
Minty honey is one thing, but I’m sure you don’t want honey that tastes like mouthwash.
Other Control Methods For Treating Varroa Mites
There are other actions the beekeeper can take in addition to the treatments to keep the count low. These methods don’t kill the mites, but they can interrupt their life cycle, which ultimately brings down the numbers.
Splitting your colonies in the summer interrupts the bee cycle because one of the new colonies will not have a brood for a few weeks.
This means that the mites cannot reproduce during this time and gives any treatment you choose a higher success rate. The same goes for requeening a colony.
This one works best with a screened bottom board. Dusting the colony triggers a grooming response. In their quest to get rid of all the unwanted sugar, they dislodge the mites that have been joyriding.
The mites then fall through the screened bottom board and out of the hive to become someone’s meal. Or, they get stuck on the varroa drawers.
Either way, they are no longer a threat. You would have to repeat the treatment weekly to be effective because it only works on the mites feasting on adult bees.
Treating Bees for Varroa Mites – What is Best?
Short answer: all of them. It is always best to rotate your treatments. If you treat once a year, don’t use the same treatment two years in a row.
For mites, an integrated pest management regimen is the best defense you can have.