In the world of beekeeping, understanding the threats to your hives is essential to maintaining healthy and productive colonies. Among the various pests and pathogens that can affect honey bees, tracheal mites (Acarapis woodi) are one of the more insidious. Unlike the more visible Varroa destructor mite, tracheal mites operate largely out of sight, burrowing deep within the bee’s respiratory system. This hidden nature makes them challenging to detect and even harder to manage without a good grasp of what to look for.
For new beekeepers, the concept of an internal parasite in a bee might sound like something out of science fiction. But tracheal mites are very real—and they’ve played a significant role in honey bee health, especially since their spread in the 1980s. They were once responsible for major colony losses and remain a concern in certain regions today, especially when colonies are already stressed by other factors such as pesticide exposure, poor nutrition, or additional parasitic infections.
In this article, we’ll take a deep dive into what honey bee tracheal mites are, how they originated, the symptoms they cause, and how beekeepers can detect and treat infestations. We’ll also explore additional considerations that can help reduce the impact of these mites and support your hives’ overall health. Whether you’re managing your first hive or adding to an established apiary, this guide will equip you with the knowledge to recognize and respond to one of beekeeping’s more elusive threats.
Where Did the Honey Bee Tracheal Mite Come From?
Honey bee tracheal mites were first identified in the United Kingdom in 1921 but likely existed well before that without detection. Native to parts of Europe, Acarapis woodi lived for centuries in relative obscurity, largely because their symptoms were often misattributed to other causes of winter loss or general colony decline. Unlike external parasites like Varroa mites, tracheal mites live inside the bee, making their presence hard to confirm without laboratory dissection and microscopic examination.
The global beekeeping community began paying serious attention to tracheal mites in the 1980s when the mites appeared in the United States and Canada. Their introduction is believed to have occurred via imported bee stock or equipment, a cautionary tale that still influences import regulations and quarantine protocols to this day. Once in North America, tracheal mites spread rapidly, aided by the close proximity of colonies, migratory beekeeping practices, and a lack of natural resistance in the local bee populations.
For a time, tracheal mites were considered one of the most serious threats to honey bee health. Entire apiaries were lost in a single season, and the beekeeping industry scrambled to find solutions. Fortunately, the severity of infestations has decreased over the years, largely thanks to selective breeding for resistant bee strains, changes in management practices, and increased awareness. However, in regions where these interventions are not in place—or when colonies are already weakened—tracheal mites can still cause significant damage.
Understanding the history and movement of this parasite underscores the importance of biosecurity in beekeeping. A pest that was once confined to a small geographic area now has global reach, reminding us that bee health is truly a shared responsibility.
Tracheal Mites Symptoms
Unlike pests that are easily spotted during a routine hive inspection, tracheal mites are internal parasites. They live inside the bee’s tracheae—tiny airways that supply oxygen to the bee’s body. The mites enter these airways through the bee’s spiracles (breathing holes) and attach themselves to the tracheal walls. There, they feed on the hemolymph (bee blood), weakening the bee and damaging its ability to breathe and regulate body temperature.
Because these mites are hidden from view, their symptoms are indirect and often confused with other problems. This makes it especially important for new beekeepers to recognize the warning signs that could indicate a tracheal mite infestation.
Common Symptoms of Tracheal Mites:
Disjointed or K-wing appearance: Bees affected by tracheal mites may hold their wings in an unusual pattern, forming a shape that resembles the letter “K.” This is caused by nerve and muscular impairment from the mites’ presence.
Inability to fly: Infested bees often struggle to fly, becoming disoriented and grounded near the hive entrance. You may notice large numbers of bees crawling on the ground, especially in cool weather.
Chilled or dead bees outside the hive: Because the mites impair the bee’s ability to regulate its internal temperature, affected bees often succumb to cold stress and are expelled from the hive or die near the entrance.
Weak or dwindling colonies in spring: One of the most telling signs of a tracheal mite problem is a colony that seems healthy in the fall but fails to build up properly in spring. Tracheal mites are often implicated in overwintering losses.
Reduced honey production and foraging behavior: Infested colonies may seem sluggish, with fewer foragers returning to the hive. This can lead to a noticeable drop in honey stores.
It’s important to note that these symptoms can also be caused by other stressors, such as viral infections, pesticide exposure, or even starvation. Because of this, definitive diagnosis often requires microscopic examination of bee tracheae. This is typically done by crushing a sample of adult bees and viewing their tracheal tubes under a microscope to look for mites or the characteristic scarring and discoloration they cause.
As a new beekeeper, don’t be discouraged if this seems like a lot to process. Over time, you’ll become more attuned to subtle changes in your colonies and develop the observational skills needed to recognize when something isn’t quite right.
Treatment for Tracheal Mites in Honey Bees
Managing tracheal mites involves a combination of direct treatment, good hive management, and, most importantly, prevention. Although these mites are no longer the top concern for most beekeepers, their presence can still be harmful, particularly in colonies already compromised by other issues. Fortunately, several effective strategies exist to control and prevent infestations.
1. Use of Resistant Bee Stock
One of the most effective long-term strategies for tracheal mite control is to use bee strains that exhibit natural resistance. Over the past few decades, selective breeding has produced lines of bees that are significantly less susceptible to tracheal mite infestations.
Resistant strains such as the Russian honey bee and certain lines of Carniolan or Buckfast bees have demonstrated better grooming behavior, thicker tracheal walls, or less favorable internal environments for mite reproduction. When starting out as a beekeeper, sourcing queens from reputable breeders who focus on mite resistance can save you considerable trouble down the line.
2. Menthol Crystals
Menthol, a compound derived from peppermint oil, has long been used as a treatment for tracheal mites. It is typically applied as crystals placed on top of the brood frames inside the hive. When the temperature rises (ideally between 70°F and 80°F), the menthol evaporates and the vapors permeate the hive, killing mites inside the bees’ tracheae.
Menthol treatments are best applied in late summer or early fall, after honey supers have been removed, as the vapors can taint the taste of honey. Consistent application for 14–20 days is usually recommended for full effectiveness.
3. Vegetable Oil Patties
Another natural treatment method involves placing patties made of vegetable shortening (like Crisco) mixed with powdered sugar on the top bars of frames. The idea is that as bees groom each other and eat the patties, the shortening coats their bodies, making it harder for mites to attach and reproduce.
These patties also stimulate grooming behavior, which helps dislodge mites. While not as immediately lethal as menthol, vegetable oil patties are a useful part of an integrated pest management approach.
4. Grease or Essential Oil Blends
Some beekeepers add essential oils like thymol, wintergreen, or eucalyptus to grease patties. These compounds may have mild miticidal properties, and when used cautiously, can support other treatment methods. However, essential oils should be used with care, as high concentrations can be toxic to bees.
5. Hive Management Practices
Good beekeeping practices also help reduce the impact of tracheal mites. These include:
Avoiding overwintering weak colonies
Ensuring proper ventilation and temperature control
Monitoring colony behavior in early spring and late fall
Keeping your bees healthy, well-fed, and stress-free is the foundation for avoiding major mite-related issues.
Other Considerations
Tracheal mites don’t exist in isolation. Like many bee health challenges, their impact is amplified when colonies are already stressed. This makes it essential to think holistically about bee health and consider the broader context in which these mites operate.
Varroa and Viral Interactions
While tracheal mites are internal parasites, their presence can weaken the immune system of honey bees, making them more susceptible to viruses like Chronic Bee Paralysis Virus (CBPV) or Deformed Wing Virus (DWV). If you’re managing other mite infestations, particularly Varroa, tracheal mites can slip in as a secondary problem that compounds overall hive stress.
Seasonality
Tracheal mites are especially damaging during the winter and early spring. Since they primarily affect adult bees and interfere with thermoregulation, they can contribute significantly to overwintering losses. Paying close attention to colony strength in the fall and taking preventative measures during this time is critical.
Regional Relevance
It’s worth noting that in many parts of North America and Europe, tracheal mite infestations have declined significantly thanks to natural selection and resistant bee strains. However, outbreaks still occur, particularly in areas where resistance traits are not widespread or where new colonies are introduced from untested stock.
Diagnostic Challenges
Since visual detection is nearly impossible, new beekeepers should not hesitate to reach out to local extension services or bee labs for testing if tracheal mites are suspected. Some labs offer low-cost or even free diagnostic services, which can help clarify what’s going on in your hive.
Final Thoughts
Tracheal mites may not be the most talked-about pest in beekeeping today, but they remain an important part of the broader honey bee health puzzle. Their subtle symptoms, internal hiding place, and potential for serious damage—especially in colder months—make them a worthy adversary for any beekeeper to understand.
For new beekeepers, awareness is your best defense. Learn to recognize the signs of a struggling colony, invest in resistant stock when possible, and don’t underestimate the power of good hive management. Combining treatment options like menthol or grease patties with a strong emphasis on prevention can go a long way in protecting your bees from tracheal mites.
As you gain experience and confidence in your beekeeping journey, you’ll become better equipped to notice the early indicators of trouble and act quickly. With vigilance, knowledge, and proactive care, you can keep tracheal mites at bay—and ensure your bees continue to thrive, pollinate, and produce delicious honey for years to come.