Varroa Mites: How to Identify, Treat, and Prevent

Varroa mites, tiny parasites affecting honey bees, have become a significant concern in beekeeping. 

These mites not only latch onto bees, feeding on their bodily fluids, but also transmit harmful viruses. The presence of these parasites can lead to bee colony collapse disorder, posing a substantial threat to pollination and, consequently, agriculture. 

For beekeepers, it’s crucial to regularly monitor hives, adopt integrated pest management (IPM) techniques, and stay informed about both chemical and natural treatments to keep these pests at bay.

What are varroa mites?

Varroa mites are tiny, reddish-brown parasites, specifically targeting honey bees. Originating from Asia, these mites have spread globally, causing significant distress within the beekeeping community. 

They attach themselves to bees, feeding on their hemolymph (akin to our blood), weakening the bee and shortening its lifespan. But their harm doesn’t stop there. 

Related: How to Deal with the Most Common Bee Diseases and Pests

Varroa mites are vectors for various viruses, further compromising honey bee health and the overall well-being of the hive. 

With the critical role bees play in food security and the environment, understanding and managing the threat of these mites is paramount for sustainable beekeeping.

Varroa mite biology and life cycle

The Varroa destructor mite is a formidable adversary for beekeepers, not just due to its parasitic nature, but also its intricate biology and life cycle that allow it to thrive within honey bee colonies. 

Understanding the mite’s biology can provide insights into beekeeping best practices and intervention strategies.

Related: Chalkbrood in Honey Bee Colonies: An In-depth Analysis of Disease Progression and Best Practices for Control

Varroa mite morphology and identification

Varroa mites have distinct physical attributes that distinguish them from other honey bee pests. 

These mites are reddish-brown in color and have a flattened oval shape, akin to a tiny flattened tick. 

Adult female mites, which are the most commonly seen, measure about 1-1.5mm in size. Their relatively large size, in the context of bee pests, allows them to be visible to the naked eye.

The mite’s body is divided into two main sections: the cephalothorax (front) and the abdomen. They possess four pairs of legs attached to the cephalothorax. 

One distinguishing feature of varroa mites is the presence of soft, fine, and short setae (hairs) covering their body. This gives them a somewhat velvety appearance.

In the context of honey bee pests, it’s essential to differentiate varroa mites from others. While mites like Tropilaelaps are also parasitic to honey bees, they are smaller and more elongated than varroa. 

Additionally, varroa mites can often be spotted on adult bees, particularly between their abdominal segments, whereas many other mites prefer the brood or other hive parts.

Related: Why Is There No Honey in My Hive? 8 Factors Every Beekeeper Should Know

Varroa mite reproductive cycle

The life cycle of the varroa mite is deeply intertwined with that of its honey bee host. 

Several factors influence the reproductive rate of varroa mites, including the availability of brood cells, the health of the honey bee colony, climatic conditions, and the presence of natural predators or other pests. 

For instance, a higher availability of drone brood cells, which are preferred by varroa mites, can increase their reproductive rate. 

Similarly, a weakened or stressed bee colony may be more susceptible to mite infestation, leading to higher mite reproduction. 

On the other hand, extreme climatic conditions or the presence of natural predators can reduce the mite’s reproductive rate.

To understand the mite’s reproductive cycle, it’s crucial to comprehend its various life stages: egg, larva, nymph (protonymph and deutonymph), and adult.

1. Egg: The cycle begins when a mature female mite enters a bee brood cell just before it’s capped. Once inside, she lays multiple eggs, with the first usually being a male, followed by several females.
2. Larva: The eggs hatch into larvae, which are legless and feed on the bee’s hemolymph. The larval stage is relatively short, lasting just a day or two.
3. Nymph: The larva then transitions to the protonymph stage, which later molts into the deutonymph stage. Both nymph stages continue to feed on the bee’s hemolymph, growing in size.
4. Adult: After the deutonymph stage, the mite molts into an adult. The male mite mates with the female mites within the same brood cell. Once matured, the females, now gravid with eggs, exit in search of new brood cells to invade, starting the cycle anew.

The entire life cycle, from egg to mature adult, can take place within a week, allowing for rapid population growth within a bee colony. It’s this fast reproductive cycle that can lead to massive infestations in a short time.

Here’s a more detailed view of the varroa mite lifecycle stages:

One alarming aspect of the varroa mite’s reproductive behavior is its preference for drone (male bee) brood cells. 

Drone brood cells are larger and have a longer developmental period, giving the mite more time to reproduce. 

This preference can lead to skewed bee populations within a hive and contribute to the overall weakening of the colony.

Varroa mite symptoms and diagnosis

Beekeepers must be vigilant and proactive in diagnosing and managing varroa mite infestations, as these parasites can significantly impact the health and productivity of a honey bee colony. 

Recognizing the signs of an infestation and employing effective diagnostic techniques are essential steps in this process.

Visible signs of varroa mite infestation

Varroa mites, while tiny, leave behind unmistakable signs of their presence in a bee colony. Some observable symptoms include:

1. Presence of adult mites: Often found on adult bees, especially between the abdominal segments. Their reddish-brown, flat oval bodies can be spotted upon close inspection.
2. Deformed wing virus: Affected bees exhibit twisted, stunted, or misshapen wings. This condition results from the viruses transmitted by varroa mites.
3. Decreased population: A sudden decline in the bee population can be an indicator, as mites weaken bees, leading to shortened lifespans.
4. Unusual brood pattern: Spotty brood patterns, with many uncapped or empty cells, suggest that larvae are dying due to mite infestations.
5. Parasitic mite syndrome: This is characterized by a combination of symptoms like discolored, sunken, or punctured brood cappings, and the presence of dead larvae in cells.

Inspecting honey bee colonies for these signs requires regular hive checks. Beekeepers should gently remove frames, closely inspecting bees, brood, and comb. Using a magnifying glass can help in spotting the tiny mites.

Diagnostic techniques for varroa mite infestation

Effective management of varroa mites hinges on accurate diagnosis. Several diagnostic methods can help beekeepers ascertain the extent of an infestation:

Sugar shake

This non-lethal method involves placing a sample of bees in a jar with powdered sugar. After shaking and allowing the bees to sit, the jar is inverted over a white surface. The sugar dislodges the mites, making them visible against the white background.

Advantages: 

• It is safe for bees and doesn’t harm them
• Straightforward to use
• Quick

Limitations: 

• It may not dislodge all mites, leading to underestimation.

Alcohol wash

Bees are placed in a jar with alcohol, which is then shaken to dislodge mites. The liquid is poured through a mesh, trapping the bees and allowing mites to fall through.

Advantages: 

• High accuracy and reliability.

Limitations: 

• Lethal to sampled bees.

Drone brood sampling 

Given varroa’s preference for drone brood, inspecting these cells can offer insights into infestation levels. Drone brood cells are uncapped, and the pupae are inspected for mites.

Advantages: 

• Allows direct observation of mite presence.

Limitations: 

• It is time-consuming and may not reflect the overall infestation level.

Tips for effective use

• Sugar Shake: Ideal for regular, quick checks throughout the beekeeping season.
• Alcohol Wash: Best used when a highly accurate measure is required, especially before implementing treatment.
• Drone Brood Sampling: Useful during the drone brood peak season.

Here’s a visual representation for more detailed information on diagnosing varroa mite infestations in their colonies:

In essence, recognizing the symptoms of a varroa mite infestation and employing the right diagnostic techniques are paramount for maintaining healthy bee colonies. 

Regular inspections and timely interventions can mitigate the impact of these detrimental parasites.

Varroa mite treatment methods

Varroa mites are among the most challenging pests beekeepers face, threatening the health and vitality of honey bee colonies worldwide. 

Effective management requires an arsenal of strategies, from mechanical interventions to biological controls. 

Each method offers unique advantages and challenges, and understanding them can empower beekeepers to make informed decisions tailored to their specific circumstances.

Related: How to Inspect a Beehive: A Beginner’s Guide

Mechanical and physical control methods

Mechanical and physical control methods provide a direct approach to managing varroa mites without resorting to chemicals. These techniques leverage simple principles to disrupt the mite’s life cycle or remove them from colonies.

Drone brood removal

Varroa mites prefer to reproduce in drone brood cells due to their longer developmental period. By adding frames designed to attract drone brood and then removing and freezing them, beekeepers can significantly reduce mite populations.

Principle: Targeting mite reproduction by removing their preferred breeding ground.

Benefits: Effective and non-toxic.

Drawbacks: It can be labor-intensive and insufficient as a standalone method.

Powdered sugar dusting

A method where bees are dusted with powdered sugar, prompting them to groom themselves and, in the process, dislodge mites.

Principle: Encouraging natural grooming behavior in bees to remove mites.

Benefits: Non-toxic and can be combined with other methods.

Drawbacks: It may not remove all mites and requires frequent applications.

Brood interruption

By periodically interrupting the brood cycle, beekeepers can prevent mites from reproducing.

Principle: Disrupting mite reproduction by halting bee brood production.

Benefits: Effective in reducing mite populations without chemicals.

Drawbacks: This can disrupt the bee colony and affect honey production.

Mechanical and physical methods offer a more natural approach to mite control, minimizing the risk of chemical residues in honey and wax. However, they may require more labor and monitoring and are often most effective when combined with other control methods.

Biological control methods

Biological control taps into nature’s own mechanisms for keeping pests in check. By introducing natural predators or agents that target varroa mites, beekeepers can potentially manage infestations without chemicals.

Beneficial mites

Some mite species, like Stratiolaelaps scimitus, prey on varroa mites. Introducing these beneficial mites into hives can help reduce varroa populations.

Challenges: It is essential to carefully manage the introduced mites to ensure their survival and prevent them from becoming a pest themselves. This requires monitoring their population growth, checking their impact on the surrounding environment, and implementing measures to control their spread if necessary.

Nematodes

Certain nematodes can parasitize and kill varroa mites. Research is ongoing to determine the effectiveness and best practices for using nematodes in beekeeping.

Challenges: One of the major challenges in using nematodes to control varroa mites is to ensure that they specifically target the mites without harming your bees. 

With this approach, it’s essential to use specific nematode species that are known to exclusively parasitize the varroa mites. 

Additionally, the timing and frequency of nematode application should also be carefully managed to ensure that the mites are effectively controlled while minimizing any potential harm to other beneficial insects.

Fungi

The fungus Metarhizium anisopliae has shown potential in targeting varroa mites. When mites come into contact with fungal spores, they become infected and die.

Challenges: The use of fungus to control pests is an innovative and eco-friendly approach to pest management. However, one of the key concerns in implementing this method is the potential harm that the fungus may cause to beneficial insects, particularly bees. 

This requires thorough research and testing to determine the impact of the fungus on the insects and to develop strategies to mitigate any potential harm. 

In general, biological control methods offer a promising avenue for sustainable mite management. 

However, they come with their own set of challenges, including ensuring that introduced agents don’t become pests themselves or harm the bee colony. Careful research and monitoring are essential to ensure the safe and effective use of these methods.

That’s why a multifaceted approach, combining mechanical, physical, and biological methods, offers the best chance of effectively managing varroa mites. 

Here is a more detailed table on the various varroa mite treatment methods, which can be especially valuable to beekeepers looking for comprehensive treatment options:

Notes:

• Efficacy rates can vary significantly based on the level of infestation, the method of application, and the presence of brood.
• Best season to apply is crucial as some treatments are less effective during the brood-rearing season or can harm the bees if applied during high temperatures.
• Application frequency and active period are based on optimal conditions and may need adjustments depending on the climate and colony health.

Prevention of varroa mites

Varroa mites have become a major concern for beekeepers around the world. 

Their presence in hives can lead to weakened colonies, reduced honey production, and, in severe cases, the collapse of entire colonies. 

Thus, it’s essential to take a proactive approach towards prevention rather than just treating infestations as they arise. 

The key to successful varroa mite prevention lies in a combination of effective hive management practices and strict quarantine and monitoring protocols.

Proactive hive management practices

Prevention is always better than cure, especially when it comes to varroa mites. Beekeepers must understand that proactive hive management practices play a pivotal role in minimizing the risk of infestation.

Maintaining strong and healthy colonies

Healthy bees are better equipped to resist mite infestations. Regular feeding, ensuring access to clean water, and protecting colonies from other pests and diseases can bolster bee health and resilience.

Role in prevention: A strong colony has a better grooming behavior, effectively removing mites from their bodies. They can also maintain an optimal brood pattern, reducing the mites’ reproductive success.

Selecting resistant bee strains

Some bee strains, such as the VSH (Varroa Sensitive Hygiene) and the Russian honey bee, have shown natural resistance to varroa mites. These bees can detect and remove mite-infested brood, interrupting the mite’s life cycle.

Role in Prevention: By choosing resistant strains, beekeepers can create colonies with innate defenses against varroa mites, reducing reliance on external treatments.

Practicing good hive hygiene

Regularly inspecting hives, cleaning equipment, and replacing old or damaged combs can help maintain a clean environment, discouraging mite proliferation.

Role in Prevention: Clean hives reduce the places where mites can hide and reproduce, thus keeping their numbers in check.

Proactive hive management not only keeps varroa mites at bay but also ensures that the colonies remain robust and productive. 

By maintaining a holistic approach to bee health, beekeepers can create an environment where bees thrive and mites find it difficult to establish a foothold.

Quarantine and monitoring protocols

Varroa mites can quickly spread between colonies, making quarantine and monitoring crucial components of an integrated mite management strategy.

Quarantine measures

Whenever new bees or equipment are introduced to the apiary, they should be kept separate from existing colonies for a period. This helps in ensuring that they don’t bring with them new mite populations or other pathogens.

Role in prevention: Quarantining new additions allows beekeepers to detect and address potential mite issues before they can spread to other hives.

Protocols for introducing new bees or equipment

Before introducing new bees, they should be inspected for signs of mites. Equipment, especially second-hand ones, should be thoroughly cleaned and, if possible, treated to eliminate any lurking mites.

Role in Prevention: These protocols minimize the risk of introducing mites into a mite-free environment.

Regular monitoring

Beekeepers should regularly inspect their colonies for signs of varroa mites. Methods such as the sugar shake or alcohol wash can be employed to assess mite levels in the hive.

Role in Prevention: Early detection is crucial. If beekeepers can identify a burgeoning mite problem early on, they can take steps to address it before it becomes a full-blown infestation.

Additional resources

Varroa mites are a serious threat to honey bees, and beekeepers must take action to protect their colonies. By learning more about varroa mites and how to control them, beekeepers can help to ensure the health and vitality of their bees.

Here are some resources that can help you learn more about varroa mites and how to protect your honey bees:

• United States Department of Agriculture (USDA)
• Bee Informed Partnership
• American Beekeeping Federation
• Varroa Mite Integrated Pest Management Guide
• Varroa Mite Treatment Options

Frequently asked questions