Understanding Varroa Mites and Their Impact on Honey Bees

Simply put, Varroa destructor (scientific name) is an external parasitic mite that attacks and feeds on our Western honey bees, Apis mellifera. The Varroa mite is considered the number one cause of death in honey bee colonies worldwide. This statement is not an exaggeration. Ongoing tracking reports over the past decade show colony losses averaging well over 40% each year, with recent losses even greater. Quote Honey Bee Health Coalition: U.S. beekeepers lost an estimated 55.1% of their managed bee colonies in 2023-24 – 14.8 percentage points higher than the 13-year average annual loss rate of 40.3%

When Varroa mites were discovered in the United States in 1987, beekeepers didn’t have the effective treatments we now possess. In those early years, much less was known about how to manage these pests. Fast forward to today, and we have developed efficient tools to manage Varroa mites—small, tick-like creatures that are highly destructive. Beekeepers now have treatment options that cater to various preferences, including mechanical, organic, and chemical methods.

Life Cycle of the Varroa Mite

Honey bees are the only host for the Varroa mite. These parasites travel from colony to colony by jumping from bee to bee while foraging or from drones that tend to drift to other hives. Once inside the hive, a mature female Varroa mite enters a brood cell just before it is capped, typically around day nine. The female then starts feeding on the developing bee. Within three days, she lays her first egg, a male, followed by additional female eggs, which mate with their brother mites. Once the young bees emerge, the fertilized mites escape to repeat the cycle.

While feeding inside the brood cell, the Varroa mite also transmits several harmful viruses, spreading them throughout the young bee population. This virus transmission leads to sick bees, causing a range of problems, including:

• Poor nursing abilities
• Poor foraging capabilities
• Shortened life-span

Mite-Induced Viruses

One of the most concerning aspects of a Varroa mite infestation is the variety of viruses they transmit. Research shows that Varroa mites spread more than 12 different viruses, which can continue to damage the bee colony for up to six months, even after the mites have been eliminated. Unfortunately, there are no effective treatments to kill these viruses. The best approach is to focus on prevention by keeping mite levels under 2 per 100 bees.

If mite levels do get dangerously high, the only known way to help combat viruses is to ensure your bees receive optimal nutrition. Providing sufficient syrup, pollen substitute, and probiotics can help maintain the overall health of the colony and mitigate the impact of viral infections.

Viruses Transmitted by Varroa Mites

Here are several viruses vectored by Varroa mites:

1. Acute Bee Paralysis Virus: Bees are unable to fly, appear dark and hairless, and may tremble near the entrance of the hive. This condition can also be caused by robbing.
2. Black Queen Cell Virus: Developing queens in queen cells die inside the cell, often appearing dark in color.
3. Sacbrood Virus: Kills larvae, leaving dark scales inside the cell. These scales are easy to remove, unlike larvae killed by American foulbrood (AFB).
4. Israeli Acute Paralysis Virus: Symptoms similar to those of acute bee paralysis, with bees appearing dark and hairless.
5. Kashmir Bee Virus: There are no visible signs, but the hive weakens due to the combined effects of Varroa mites and the virus.
6. Deformed Wing Virus: One of the most obvious signs of Varroa infestations—newly emerged bees have crumpled and deformed wings and are unable to fly.
7. Chronic Bee Paralysis Virus: Adult bees display an inability to fly, tremble at hive entrances, and have extended abdomens and darkened bodies.

How to Control Varroa Mites

The first and most important step in controlling Varroa mites is regular testing. It is essential to develop a consistent testing schedule to monitor mite levels, and it is recommended to test at least once a month. However, quarterly testing is more common among many beekeepers. Consistent monitoring ensures that infestations can be detected early, preventing severe damage to the colony.

Natural and Chemical Varroa Treatments

Regardless of your preferred method for treating a Varroa infestation, it is important to learn about each of them, understand how to test for mites, and choose a treatment method that works best for your hive. One of the most debated topics in beekeeping is whether to use natural (organic) or chemical treatments for controlling Varroa mites. The key to answering this question lies in educating yourself about both options.

Once you understand the pros and cons of both natural and chemical treatments, you will be better equipped to make an informed decision. Below are a few helpful tips for both approaches:

1. Read the Manufacturer’s Instructions: Whether using natural or chemical Varroa treatments, always follow the manufacturer’s instructions carefully. They provide essential guidance on the proper application and any necessary safety precautions.
2. Focus on Bee Health: For new beekeepers, the primary focus should be on learning about bees and keeping them healthy. Controlling Varroa mites without the use of synthetic miticides can be challenging, and it requires significant skill and commitment. Do thorough research before choosing this path.
3. Consider the Costs of Chemical-Free Treatment: It’s possible to control mites with minimal chemical intervention, but doing so requires consistent effort, extensive testing, and often more financial investment. Most beekeepers who start with natural treatments find it difficult to maintain the necessary consistency over time.

Striking a Balance Between Natural and Chemical Treatments

For most beekeepers, combining mechanical, natural, and chemical Varroa treatments is the most effective approach to managing mites. By using natural methods when possible and resorting to chemical treatments when necessary, beekeepers can strike a balance that ensures their bees remain healthy and their hives stay productive.

Conclusion

Varroa mites pose a significant threat to honey bee health worldwide. These parasitic mites not only contribute to colony losses but also spread devastating viruses that affect the entire hive. By regularly testing for Varroa mites and employing both natural and chemical treatment methods, beekeepers can control infestations and protect their colonies from long-term damage. Through educational beekeeping blogs, consistent care, testing, and treatment, we can safeguard the future of honey bees and the essential role they play in pollination and food production.