Mite Treatment for Bees: How Beekeepers are Vital to Saving The Honey Bees

Mites are found on bees worldwide. In a perfect world where everything stays put in the place it originates in, mites wouldn’t be a widely discussed topic. The mites would inevitably kill a few bees by feeding on their blood and transmitting pathogens in the process, but the bees they evolved with wouldn’t be bothered as they would have developed defenses against the mites in their long history together. Globalization means that nothing is restricted to the corner of the world from which it originally came. In some instances we can be grateful for this, I couldn’t eat a mango in the arid desert of Colorado if this wasn’t the case. In other instances, we see the immense damage that is done when one wee bugger decides to jump on a cruise from Asia to the Americas as is the case with the Emerald Ash Borer, an invasive species that destroys ash trees after hitching a ride on imported, untreated wood.

In Asia, the mite Varroa destructor was coevolving with the Asian species of honey bee (Apis cerana). Their long history together means that the Asian honey bee isn’t much troubled by Varroa; the poor European honey bee (which is the most widely managed bee throughout the world for honey production) is maladapted to living with the mites, which is why the mite is so aptly named Varroa destructor. They can collapse whole colonies in a matter of a season, weaken the bees by feeding on their blood (hemolymph), and introduce pathogens that cause further damage and death.

When I originally bought my first few hives, they were established colonies that I got from a lady who had been beekeeping for the last decade and was ready to pass the torch. She advised me that she kept bees for a long time, but was never a successful beekeeper until she started treating for mites. It doesn’t matter if you do everything else right as a beekeeper, not monitoring your hives and treating for mites will always result in the loss of the colony.

Humid places tend to struggle with mites worse than temperate climates simply because mites favor a more humid environment, but no one should rule out the presence of mites just because they live in drier climates.

Honey Bee Defenses

Some hives tend to be better adapted to warding off mites. One of the big factors is cleanliness. Like humans, some hives tidy up a bit better than others. It starts at the entrance of the hive with the guard bees. In an extremely clean hive, the guard bees are extra diligent in checking that their sister bees aren’t returning to the hive with anything clinging to them, and each individual bee will have a higher rate and standard of grooming. The nurse bees also detect when brood have been infected and remove them from the hive.

Some beekeepers and researchers noticed certain bees were less susceptible to collapse by Varroa. Russian Honey bees are naturally more resistant to Varroa because of their long history together. Going back to cleanliness, these bees show highly adapted behavior in identifying and removing infected brood and a generally higher standard of grooming. These bees developed a genetic resistance against the mites and breeders began using Russian bees to select for this trait. Now, bred bees like Belfast bees are widely available to beekeepers who want a level of protection awarded to their bees through genetics.

Meet the Mites

Two different mite families target honey bees, tracheal mites and Varroa. Thankfully, some treatment options kill two mites with one stone (formic acid). This article will focus on Varroa treatments as the losses of honey bee colonies to tracheal mites are greatly overshadowed by losses due to Varroa. Varroa is specially adapted to target honey bees as the host. As mentioned before, the Asian honey bee (Apis cerana) was its original host. With the movement of the mite further west, it stumbled on the European honey bee and found it closely related enough to its Asian host to be suitable.

Adult Varroa hides on the abdomen or under the wings where they are less likely to be groomed off and can transfer between bees or make their way on foot to the brood chamber once inside the hive. They will be especially likely to choose a drone cell if available, as drones pupate slightly longer than a worker or queen bee. After the mite finds a brood cell, she lays up to 6 eggs, male and female. While the honey bee pupates after being capped off with wax by the sister bees, the mite eggs hatch and mate within the cell before the honey bee finishes pupating and chews through the wax capping, unknowingly releasing the fertile females onto her hive mates. Mites are a problem not just because they weaken the bees by feeding on their blood but they can introduce bacteria and viruses into the honey bees that cause further damage and death.

Determining the Need for Mite Treatment of the Bees

Before deciding on a mite treatment for the bees, carry out a test to determine how many mites are present in the hive so treatment doesn’t take place unnecessarily. Both test methods require the collection of about 300 bees (about a half cup). The bees most likely to have Varroa are the nurse bees, as they recently emerged from the brood cells themselves, and come into close contact with the brood. Your queen should NOT be a part of the sample so make sure she doesn’t get caught up in it.

Sugar Shake: This method isn’t as accurate as the alcohol wash but doesn’t kill any bees. Using your 1/2 cup of bees in a mason jar with a mesh lid. Pour a few tablespoons of powdered sugar on top of the bees and shake for about a minute. After the bees are coated in the sugar, give them a bit of time. They will groom themselves and dislodge some mites in the process, and you don’t want to rush them. Repeat this process once more before you release your bees (suited up because they will be pissed about you covering them in sugar and shaking them). After several minutes, shake the jar upside down and empty the powdered sugar onto a clean plate.

Determining how many mites are in the hive approximately requires counting the number of mites on the plate, dividing that number by the # of bees in your sample, and then multiplying by 100.

Let’s say you had 8 mites on your plate. 9 mites / 300 bees x 100 = 3%, so you have a 3% mite population in your hive and anything at or above 3% is when treating your bees for mites becomes necessary.

Alcohol Wash: The same collection method applies for the alcohol wash, but in this case, they will be dumped into a jar containing alcohol. Shake the bees for a minute and then dump the alcohol and mites onto a clean plate, using the mesh to keep the bee bodies from falling onto the plate. The same calculation applies to the alcohol wash as the sugar shake, so calculate the percentage of mites in your hives to determine the need for treatment.

Mite Treatment for Bees: Methods and their Pros and Cons

Several different types of mite treatment for bees exist, all with their own stipulations. Review all your options and ensure you meet the criteria for the treatment you choose before you proceed; some treatments won’t be as effective and others cause stress and damage to the bees if applied incorrectly. All the treatments I mention are sourced from plants.

Formic acid

It is highly corrosive and toxic to humans, so extreme care must be used when handling. It’s administered as strips or pads placed between the frames or on top of the hive bars. The formic acid-soaked item creates fumes that permeate throughout the hive for a few weeks before being removed. Formic acid is one of the compounds known to penetrate brood cells, making it one of the most effective and widely used mite treatments for bees.

Still, it is not without limitations as it can’t be used when Honey supers are present and above 80 degrees can cause damage to the bees within the hive. Formic acid is a formidable substance in its effects on Varroa but must be used cautiously because of its potency.

Formic acid also kills tracheal Mites, although these Mites are much less widespread. The only way to know tracheal mites have infected your hive is to send some of the bees to a lab for dissection. Watch out for the “K” wing, bees holding their wings at an odd angle or irregular flight; it could be tracheal mites affecting the bees’ ability to breathe, however, these are also symptoms of other problems which is why a lab test is the only way to diagnose tracheal mites.

• effective against mites within capped brood cells
• Temperature sensitive; must be between 55 degrees and 80 degrees FHT both to be effective and to avoid harming the brood and queen
• Not suitable for use when honey supers are present

Oxalic Acid

Oxalic acid has two methods of application, the dribble method and vaporization. Neither method penetrates brood cells, so it’s essential to treat in the very early spring before the queen starts laying or fall/winter after the brood has all hatched; the temperatures are more optimal for oxalic acid treatment during these times as well.

Dribble method: The dribble method uses oxalic acid powder mixed into sugar syrup. The ratio is about 2.5-3.5 grams per liter of sugar syrup. Using a squeeze bottle, the mixture is dribbled directly onto the bees. 50-60 degrees FHT is optimal as the bees will likely still be clustered together. Aim to use a few tablespoons of syrup per frame, and only treat frames that contain brood as that is where the mites will be. This method shouldn’t be used when honey supers are on the hive as the bees might mix some of the oxalic sugar syrup in with the honey.

Vaporization method: using a vaporizer specific to oxalic acid is more effective than the dribble method and can be done without opening the hive. Vaporization needs to happen below 50 degrees. Using this method also doesn’t require that honey supers to be removed; vapors will quickly disperse and evaporate so there is no prolonged contact with the honey.

• Not effective against mites that are in capped brood cells
• 40-50 degrees is optimal for both dribble and vaporization
• Safe for use while honey supers are present

Thymol

Thymol comes in pads or strips that are placed within the hive where the thymol evaporates slowly. They are left for about 2-4 weeks, so the temperatures must remain within the instructed range, about 50 degrees to 80 degrees FHT. If the temperatures drop a bit below or above these temperatures, it’s not so much a danger to the bees as it’s just not as effective. It should work as long as the temperature is in this range for most of the treatment cycle.

Thymol is also not effective in Varroa found inside brood cells where they typically like to hang out, so treat your hives when no brood is present. If you must treat while brood is present, it’s important to treat again after the brood hatch. Drones have a development cycle which is about 24 days from egg to emergence as an adult. They pupate for about 14 days which is the stage in which the varroa will be inaccessible, so 14 days after your first Thymol treatment, ensure that you are adding more strips or pads according to the label. If the pads or strips you’ve purchased have a 4-week treatment period, that should be sufficient.

• Not effective against mites that are in capped brood cells
• 50-80 degrees FHT is optimal
• Safe for use while honey supers are present

Because of how mite treatments work, usually by dispersal as a fume, temperature always plays a role in how it will disperse throughout your colony. Unfortunately, no treatment exists where temperature can be completely ignored. This is why treatments are usually performed in the early spring or late fall.

So many factors play into what treatment works best. The Honey Bee Health Coalition has a wonderful in-depth guide for managing Varroa and protecting Honey bees is at the heart of their mission. You can check out their guide here. The flowchart below aids in the decision of which treatment mentioned is the best for your situation.