Varroa Mite Treatment: Strategies And Best Practices

Varroa mites, scientifically known as Varroa destructor are quite the headache for my honeybee colonies and me. If left without varroa mite treatment by us beekeepers, varroa mites harm individual bees and the overall health and productivity of my colonies.

They have spread globally and have since become one of the most significant threats to honeybee populations worldwide. The pesky little invaders live in the honeybee brood and then to multiply quickly if left unattended.

A solid strategy for varroa mite treatments is crucial. Getting your treatments right – using the right tools, chemicals, and timing – is essential for keeping their numbers under control.

The battle against varroa mites is ongoing. As beekeepers, we must stay informed about the latest information and tools for varroa management. Hence, I have put together this handy guide on varroa mite treatment – to help out my fellow beekeepers.

Understanding Varroa Destructor Mites

What is Varroa Destructor?

Understanding Varroa destructor is vital for effective management and varroa mite treatment in beekeeping. These tiny troublemakers, known simply as varroa, are ectoparasitic mites that prey on honey bees. They’re small, reddish-brown creatures that latch onto both adult bees and brood, feeding on their fat body tissue.

They are believed to have originated from Asia, specifically from the region around the Asian honeybee (Apis cerana). Varroa likely transitioned to the Western honeybee (Apis mellifera) when the latter was introduced to regions where the two species coexist.

The varroa mites quickly spread globally and have since become one of the most significant threats to honeybee populations worldwide.

Varroa Lifecycle and Reproduction

The life cycle of varroa mites is like something out of a science fiction movie. It starts when a female mite sneaks into a developing bee cell just before it’s sealed by worker bees. Inside the bee cell, the female mite lays multiple eggs.

As the bee larva grows, so do the mites, feasting on their host. When the new bees emerge, so do the mature male and female varroa mites, ready to wreak havoc on the colony once again.

The Significance of a Varroa Infestation

Varroa infestations can have severe consequences for bee colonies. The varroa mites weaken bees by feeding on them, multiplying quickly if left untreated and spreading viruses. This can potentially lead to colony collapse. It’s crucial for us beekeepers to stay vigilant and employ effective varroa mite treatment.

Early Detection and Monitoring

Being on the lookout for varroa mites is part and parcel of our job as beekeepers. Spotting them early and keeping a close eye on their numbers is key to managing these pesky critters and keeping our colonies thriving.

Signs of Varroa Infestation

Knowing what to look for when it comes to varroa mites is a big part of the battle. Keep an eye out for things like bees with wonky wings (a sign of Deformed Wing Virus), which often comes hand in hand with a high varroa count.

You might also notice bees kicking the bucket sooner than they should or funky patterns in the brood. It’s all about staying alert and spotting the signs early on when inspecting your beehives.

Testing Infestation Levels

Beekeepers use a variety of testing methods to accurately monitor mite populations and assess the health of their honeybee colonies. In the past, the alcohol wash method was commonly used. But since this involves drowning bees in alcohol I will not go into any further details. It’s old news and outdated.

Instead, let’s focus on the sugar roll test and natural mite drop test, both of which provide valuable insights without harming the bees.

Sugar Roll Test

Many beekeepers advocate for the sugar roll test. Here’s how it works: A small sample of adult bees is collected from the hive and placed in a container. Powdered sugar is then added and gently mixed with the bees.

The sugar acts as an irritant, prompting the mites to detach from the bees› bodies and fall into the sugar. After a few minutes of shaking, the sugar and mite mixture is sifted through a mesh screen to separate the mites from the bees.

The number of mites collected in the sugar can be counted to estimate the level of varroa infestation in the hive. The varroa mite count should not exceed 1 mites per 100 bees in spring and 2 mites per 100 bees the rest of the year.

Natural Mite Drop Test

I personally opt for the natural mite drop method. It’s a passive method where I simply monitor the number of mites that fall onto the aluminum varroa mite screen in the bottom board of my Dadant beehives.

The instructor in my beekeeping course emphasized that a quick glance at the monitoring screen is often sufficient to gauge the severity of the varroa infestation. He’d use a simple assessment like “that’s a lot of mites” or “that’s not a lot of mites” and then think about the further steps necessary.

Beekeeping can be as simple as that. For me, this straightforward approach has proven effective over the years.

If you really want to count varroa mites, the government here in Switzerland suggests the following:

• Count the varroa mites that have fallen onto the varroa mite screen within 7 days
• Do a varroa mite count at the end of May, the count should not exceed 7 mites/day
• Do another varroa mite count at the end of June, the count should not exceed 10 mites a day
• Do third varroa mite count at the end of October, the count should not exceed 5 mites a day

Accordingly, if the amount exceeds the suggested mite count, you should put the entire onto completely new frames to get rid of all the varroa mites that are sitting in the brood of the hive. This seems excessive at first, but can be easiliy done and is very, very effective. I will write a little blog post about it in the future.

What seems excessive is very, very effective. I personally have never done it, as I don’t count mites and just do the necessary treatments anyway. In years, I have never lost a colony to varroa mites and have had the under control. Some years there were more varroa mites, some years there were less.

Seasonal Considerations for Varroa Mite Treatment

Varroa mites live in your bee colonies year-round, both in capped cells and in the open hive. Most beekeepers use a varroa treatment strategy which involves both mechanical and chemical treatments, which are drone brood removal (mechanical), and oxalic and formic acid (chemical). I will go into detail about those in the next couple of paragraphs.

Effective varroa mite control hinges on understanding and leveraging seasonal cycles of both the bees and varroa mites. I tailor my treatment strategies to different times of the year to maintain healthy beehives.

Spring and Summer Management

In spring and early summer, the challenge is keeping varroa mite populations in check as hives thrive and grow. During this period, it is crucial to monitor mite levels, regularly using the monitoring and detection methods I talked about earlier.

A very underestimated way of managing varroa mites is by frequently and often replacing old and dirty frames by new ones. The newer and cleaner the honeycomb in your beehives is, the better. It’s simply good beekeeping practice to do so anway, regardless of the varroa mites.

In the warm months, you can use both mechanical and chemical varroa mite treatments. I will go into detail about them in the next paragraphs.

Treatment selection should consider the presence of closed and capped brood cells, effectiveness at current temperatures, and compatibility with honey production in spring and summer.

Treating Colonies with open Brood Cells

During the warm months, swarming activity increases. You might gather swarms or split existing hives because they become too large, to reduce swarming activity. These new colonies will require their initial chemical varroa treatment. Oxalic acid is commonly used for this, as there won’t be any capped brood cells.

Treating Colonies with capped Brood Cells

Right after the honey harvest in summer a first chemical treatment with formic acid is due for your honey producing colonies which will have capped brood cells. This can only be done when there’s no honey left to be harvested, as the formic acid might penetrate into it.

Winter Management

Heading into fall, beekeepers must prepare their hives for winter, a critical time when bee populations dwindle and mite loads can become detrimental.

A late summer or early fall treatment can help reduce mite levels before bees enter the winter cluster phase. Nevertheless, a second treatment with formic acid is due once you have prepared your bee colonies for the winter.

Another treatment with oxalic acid right around Christmas time (targeting a broodless period in the hive) puts additional pressure on the varroa mites and lets the bees start the new year with the lowest number of varroa mites possible.

This treatment timing is crucial to ensure that the bees going into winter are healthy and free from high mite loads which can compromise the hive before spring.

Now, let’s look at the mechanical and chemical varroa mite treatments in detail.

Mechanical Varroa Mite Treatment: Drone Brood Removal

Drone brood removal is a mechanical method of varroa mite treatment employed by beekeepers to disrupt the mites› reproductive cycle.

Varroa mites have a preference for drone brood cells due to their longer development period, making them ideal breeding grounds. By selectively removing frames that carry a lot of drone brood from the hive, beekeepers can also remove a significant portion of the varroa mite population.

This method can be an effective component of an integrated pest management strategy aimed at reducing varroa mite infestations in honeybee colonies.

BUT! While drone brood removal can help reduce varroa mite populations in beehives, it should not be considered a standalone solution for varroa mite treatment. Often, drone brood removal is combined with chemical varroa mite treatment.

Personally, I’m not a fan of drone brood removal since it reduces the number of drones in your hive. Drones are indispensable in a bee colony’s life cycle, particularly in mating with queen bees. Therefore, I see absolutely no sense in removing drone brood frames.

Chemical Varroa Mite Treatment

When it’s time, it’s time. Unfortunately, just monitoring the varroa mites and the frequent drone brood removal just isn’t enough. Without proper varroa mite treatment, there will be too many of them soon.

Beekeepers have a range of chemical treatments at their disposal to combat Varroa mite infestations, each with specific active ingredients and application methods.

These treatments can be broadly categorized into organic acid treatments, synthetic acaricides, and formulations containing essential oils or other compounds.

Organic Acids for Varroa Mite Treatment

Organic acids, such as formic acid and oxalic acid, are naturally occurring compounds that are used to treat Varroa mites.

Formic acid treatments have the distinct ability to penetrate the capped brood where Varroa mites often reside, reaching the mites where they reproduce.

Oxalic acid treatment, on the other hand, is typically applied via trickle method or vaporization, and is most effective when the hive has little to no capped brood.

Synthetic Acaricides for Varroa Mite Treatment

Synthetic acaricides are chemical agents specifically designed to control mite populations. One of the most common active ingredients in these products is tau-fluvalinate, found in treatments like Apivar.

Amitraz, another potent active ingredient, also used in products like Apivar and effectively interrupts the life cycle of the mites.

Essential Oils and other Compounds for Varroa Mite Treatment

Compounds derived from essential oils, like thymol, can be used to treat Varroa mites with a mode of action that exploits their natural toxicity to mites, but with minimal impact on the bees.

Products that incorporate these natural compounds offer an alternative to beekeepers that want to reduce the risk of chemical residues in the hive.

Why I exclusively use Organic Acids for my Varroa Mite Treatments

Ultimately, the choice of varroa mite treatment boils down to the personal experience and knowledge of each beekeeper. For me, organic acids have been the preferred option.

Since the beginning of my beekeeping journey, I’ve relied on oxalic and formic acid for the varroa mite treatments in my honeybee colonies. It has consistently proven to be highly effective while causing minimal impact on my bees when applied correctly.

Moreover, ample knowledge of thousands of beekeepers and scientific research, suchs as studies published in the Journal Of Economic Entomology and the Journal of Apicultural Research, have highlighted the efficacy of formic and organic acids in combating varroa mites.

A Guide to Oxalic Acid

Oxalic acid is a naturally occurring compound found in many plants such as rhubarb and spinach, which can be synthesized in the laboratory. The timing of oxalic acid varroa mite treatments is critical for maximum effectiveness.

Since oxalic acid does not penetrate capped brood cells, where varroa mites develop, it is crucial to ensure that a significant portion of the mite population is exposed.

Treatments are typically conducted during periods of minimal brood rearing, such as winter, when hives have been newly split, or a captured bee swarm has been introduced into their new hive.

How to apply Oxalic Acids to Bee Colonies

There are several ways to apply oxalic acid to bee colonies.

The Dribble Method

This involves dribbling a solution of oxalic acid mixed with sugar syrup onto the bees between the frames. A sugar syrup solution is used as a carrier for the oxalic acid.

The solution is made by dissolving a specific amount of oxalic acid in a measured quantity of warm sugar syrupy water. The concentration of the acid is crucial and should be accurately measured to avoid over- or under-dosing.

With the oxalic acid solution prepared, it’s time to apply it to the bees. The dribble method involves gently dribbling the solution onto the bees between the frames and the hives using a syringe.

As the bees clean the oxalic acid syrup off each other, they inadvertently ingest it. This syrup then enters the metabolism of the mites, which feed on the bees’ fat body tissue now containing oxalic acid. While bees survive this process, the mites do not. Checkmate!

Make sure you wear protective gear including gloves, goggles and a mask to shield yourself from direct contact with the acid solution and fumes.

The Spray Method

Some beekeepers use a spray bottle to apply oxalic acid solution directly onto the bees and hive components. They prepare an oxalic acid solution by dissolving the appropriate amount of oxalic acid in water to achieve the desired concentration for treatment.

Using a handheld sprayer or specialized spraying equipment, they apply the oxalic solution directly onto the bees, comb surfaces and components. Ensuring thorough coverage of all frames, they focus on areas where mite infestations are most prevalent.

The Vaporization Method

The vaporization method with a piece of equipment called Varrox-Eddy has been my preferred way to apply oxalic acid, and I think a vaporizer should be part of any well-equipped beekeeping kit. A specialized tool called “Vaporizer” is used to heat powdered oxalic acid crystals, creating a vapor that permeates throughout the hive.

The bees come into contact with this vapor as they move about the hive, effectively exposing the mites to the acid. Similar to the dribble method, the oxalic acid enters the mites metabolism, ultimately leading to their welcome demise.

This method has a proven track record of over 90% lethality for varroa mites in a beehive due to its thorough coverage of the hive and is relatively quick and easy to administer.

When using the vaporization method, it’s crucial to prioritize safety. Wear gloves and a mask, ensure adequate ventilation in the beekeeping area and prevent coming into direct contact with the acidic fumes.

A Guide to Formic Acid

As oxalic acids only target varroa mites in the open beehive and uncapped brood cells, your varroa mite treatment strategy should also involve formic acids, which will also enter capped brood cells, where the varroa mites develop.

Formic acids are typically administered during the warmer months of the years when honeybee colonies are the most active. This timing allows for optimal treatment effectiveness. It ensures that the treatment targets the highest concentrations of varroa mites within the colony. The bees are more actively engaged in breeding, their numbers are at their highest and they are more actively engaged in grooming and distributing the acid throughout the hive.

Formic acids can be bought in specialized online or offline stores as readily mixed solutions in different percentages or strengths.

As they are quite aggressive chemicals, it’s very important to refer to specific formic acid treatments plans to not overexpose the bees to the acid. Also, formic acid varroa mite treatments are more temperature sensitive, which is why I would always opt for specifically designed applicators.

How to apply Formic Acids to Bee Colonies

An old-school method of formic acid application involves placing a single, unprotected, and soaked pad of formic acid onto the frames of bee colonies. This approach overlooks crucial factors as evaporation rate, bee health and beekeeper safety. Therefore, I won’t delve deeper into this method.

Instead, let’s explore modern applicators for formic acid, which offer safe and effective alternatives for the varroa mite treatment of your bees. Among these, three dispensers stand out for their widespread use and success.

The Liebig Dispenser

The Liebig Dispenser is a simple and widely used formic acid dispenser, which uses a small container for the formic acid and thin absorbent paper pads. It is placed upside down right on the hive frames.

The formic acid is filled into the container, ensuring minimal exposure for the beekeeper. The bottle is then inverted and placed on the base plate, which allows the acid to penetrate the paper pad below and vapor to reach the bees.

Liebig Dispensers are easy to use and relatively inexpensive, but their evaporation rate is susceptible to temperature fluctuations. I have used them in too hot temperatures, which has left the formic acid to evaporate way too quickly. Not nice for the bees!

The Nassenheider Dispenser

Nassenheider dispensers are ultimately a more sophisticated and expensive version of the Liebig dispensers. They offer more of a “set-and-forget” approach with less need for adjustment and monitoring.

What makes them stand out is the so-called “wick”. The wick acts as a bridge between the formic acid reservoir and the surrounding air within the hive. The wick restricts the total surface area from which formic acid can evaporate, inherently slowing down the evaporation rate also in high temperatures. The formic acid slowly evaporates from the wicks’ surface into the hive air.

This unique design contributes to the controlled release of the formic acid. Compared to the paper pads of Liebig dispensers.

The FAM-Dispenser

FAM (Formic Acid Migratory) dispensers are widely used by beekeepers here in Switzerland, particularly for their compatibility with traditional Swiss type beehives or beehouses. While they are commonly used in this setting, they are versatile enough to be used in various types of hives.

In my own beekeeping practice, I rely exclusively on FAM dispensers for the varroa mite treatment.

FAM dispensers come in three pieces. A bottom piece, which is a plastic cardboard tray, a sponge pad that is soaked with formic solution, and a plastic top cover with a disc that lets the beekeeper adjust the opening of the cover based on the ambient temperatures during the varroa mite treatment.

Once everything is set in place and ready, the complete FAM dispenser installation is put onto the frames in the beehive upside down, which results in a constant and controlled flow of formic acid vapor into the beehive.

I have had great success using FAM-dispensers for my treatments and can highly recommend them.

There you have it!

I know that his was a lot of information to digest so below, I have condensed the varroa mite treatments in blog post into two little comprehensive tables for you. You can also download them as a PDF too, if you like. I hope that helps!

Remember to stay informed about the latest developments in varroa management and always prioritize your own health and safety. With the right knowledge and tools at your disposal, you can successfully combat varroa mites. To battle!

Varroa Mite Monitoring

Monitoring Method	Recommended Time	Tools Used	Additional Notes
Visual Inspection	Regularly throughout the year	Beekeeping suit, smoker, hive tool	Check for signs of mites on adult bees, brood, and hive debris.
Sugar Roll Test	Throughout the year, especially in summer	Jar, powdered sugar, mesh screen	Provides an estimate of mite infestation levels by dislodging mites from adult bees. Mite count should not exceed 1 mite per 100 bees in spring and 2 mites per 100 bees the rest of the year.
Natural Mite Drop Test	Throughout the year, especially in winter	Varroa mite monitoring screen, hive tool	Measures mite fall onto a monitoring screen placed under the hive.

Varroa Mite Treatments

Treatment Method	Application Time	Tools Used	Additional Notes
Drone Brood Removal	When drone brood is present	Hive tool, frame grip	Effective mechanical method to disrupt mites› reproductive cycle.
Oxalic Acid Treatment	Spring, Summer, Winter – after hive splitting, or introducing bee swarms and for the winter treatment around Christmas time	Vaporizer, dribble method kit, sprayer	Does not penetrate capped brood cells; effective during broodless periods.
Formic Acid Treatment	Warmer months (spring to early fall)	Liebig dispenser, Nassenheider dispenser, FAM-dispenser	Targets mites in capped brood cells; should be applied cautiously to avoid harming bees.
Other Chemical Treatments	Varies	Varies	Include synthetic acaricides and compounds derived from essential oils; follow manufacturer’s guidelines for application.

Frequently Asked Questions

In this section, let’s address common concerns and provide practical guidance to beekeepers tackling varroa mite infestations in their beehives.

What treatments are available for controlling Varroa mite infestations in honeybee colonies?

A range of treatments exists for controlling Varroa mites, including mechanical treatments such as drone brood removal and organic acids such as oxalic acid and formic acid. The choice of treatment can depend on factors like the level of infestation, time of year, and local regulations.

Can beekeepers safely apply oxalic and formic acid to treat Varroa mites?

Yes, but beekeepers must ensure that the concentration is effective enough to tackle the mites while not harming the bees, and it’s crucial to follow safety protocols, such as wearing protective gear such as goggles, gloves, protective clothes and appropriate face masks. Always follow label directions for application!

When should beekeepers typically administer treatments to prevent Varroa mite infestation?

Treatments should be administered the warm months of the years when hive activity is at its peak, and in fall, to reduce mite populations before winter. In winter, further treatments should take place. Regular monitoring is essential to determine the optimal timing for treatment.

Are there any natural methods effective in eliminating Varroa mites from bee hives?

Natural methods, such as mechanical drone brood removal and selective breeding for mite-resistant bees, can be effective. Additionally, managing hive conditions to discourage mite reproduction is beneficial. However, these methods might need to be supplemented with other treatments for full effectiveness.

What are the best practices for using formic acid in Varroa mite treatment?

Best practices include using formic acid during the warmer months when the temperatures are within the recommended range for the product being used. Care must be taken to follow the manufacturer’s guidelines on dosing and application intervals to ensure efficacy and safety for both bees and beekeepers.

What are the signs that it is too late to treat a bee colony for a Varroa mite infestation?

Signs that it may be too late include severe population decline, the presence of deformed wing virus, and dwindling brood. At advanced stages, the colony might be beyond recovery, and the focus should shift to prevention in other hives.