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Tracheal mites (Acarapis woodi) are microscopic parasites that infest the tracheae of honey bees, causing acariasis or acarine disease. These mites were first reported in the US in 1984 and have since spread to all beekeeping states. They pose a significant threat to beekeeping, with infestations leading to weakened bees, reduced oxygen flow, and ultimately, bee death. The mites affect all classes of bees within a colony and are difficult to detect without lab testing. Infested bees may exhibit disjointed wings and lethargy, often crawling near the hive entrance before dying.
Controlling tracheal mites is challenging, with no fully effective control measures. However, cultural practices, such as maintaining hive hygiene, using mite-resistant bee strains like Buckfast bees, and proper apiary location to exploit higher mite mortality in warmer conditions, can help. Chemical treatments include miticides like menthol crystals and formic acid-based products, although their use is regulated and requires caution. Essential oils, such as wintergreen oil, have shown some effectiveness but are not reliable on their own.
Preventative measures are crucial, with selective breeding for mite resistance and good apiary management practices being the first line of defense. While menthol is FDA-approved for tracheal mite control in the US, other substances like Apiguard (thymol-based) also show effectiveness. Beekeepers must follow manufacturer directions and regulatory guidelines to minimize risks to bees and the environment.
What are Tracheal Mites?
The tracheal mite, while not native to America, was first reported in Texas where, in 1984, a commercial apiary operation tested positive for the mite. It has by now spread to all the beekeeping states in the USA despite a huge effort to control the spread by destroying infected colonies. The parasite is spread easily among colonies by drifting bees and through any activity where live bees are moved around colonies. Honey bees contaminated with mites have been found in randomly selected swarms (colonies) and even in packaged bees and queens. This guide takes you through treating tracheal mites (Acarapis Woodi) in honey bees.
The tracheal mite is a microscopic parasite that lives and reproduces in the trachea of European honey bees (EHB). Adult tracheal mites invade the tracheal system of a bee, where the female lays eggs which mature in 10 to 15 days. In the tracheal system, the eggs will hatch and mature into adults thus clogging the breathing system. Clogged breathing tubes reduce the flow of oxygen in adult bees which will eventually kill them.
The ease of spreading the parasite and the difficulty of detecting it, present a very serious threat to honey production. There is thus a need for beekeepers to control the infestation. The parasite is thought to be responsible for 20 to 50% loss of bees in colonies in the state of Tennessee alone, with some operations reporting losses of entire colonies.
Effects of Tracheal Mites in Beekeeping
Tracheal mite infestation (called acarine disease or acariasis) in honey bee colonies across America has continued to wreak havoc in commercial apiaries with devastating consequences. The pest is credited with causing huge losses of bee colonies and the subsequent decline in honey production. Some apiaries have lost their entire bee population, while others are forced to destroy colonies. The bottom line is that without control the pest will continue to pose a very serious threat to beekeepers across the country.
Signs of Tracheal Mites in a Beehive
There are no reliable indicators of tracheal mite infestation through mere observation of a colony. However, certain behaviors exhibited by bees may indicate the presence of the mites. Bees infected with the tracheal mite exhibit signs of weakness, that include the inability to fly and general lethargy among the worker bees. The wings of infected bees are typically disjointed, projecting about 90 degrees from the axis of the body, and are often unhooked with the hind wing projecting 90 degrees from the axis of the body. Bees affected also exhibit distended abdomens.
Since the bees are unable to fly, they can be seen crawling about the hive entrance. Infected bees have been observed to exit the colony and die. The disease reduces the lifespan of the bees and ultimately the level of honey production.
Unfortunately, Nosema and some viral infections show the same symptoms. Microscopic examination of the trachea in a lab is the only way to truly confirm a tracheal mite. Beekeepers should send samples of suspected colonies to a lab for testing. Both beginner and experienced beekeepers can collect samples for lab testing.
Treatments for Tracheal Mites
There is presently no good control measure for controlling this mite. For beekeepers with colonies that have no tracheal mite infestations, preventive measures should be prioritized. Beekeepers should maintain good hive hygiene and make regular check-ups as a basic preventive measure.
Where attacks have already occurred, various cultural practices, as well as the use of miticides can be employed to control and eliminate infestation of the tracheal mite in honey bee colonies. Currently, no biological measures are available for the control of the tracheal mite.
1. Cultural Methods
Cultural control methods appear suitable since the parasite dies within a few hours outside of the host. The pest cannot, therefore persist for long on combs or other colony and environmental components to contaminate other colonies. This fact can be exploited to halt the spread.
Use of Tracheal Mite-Resistant Lines of Bees
Among commercially available European Bee strains, Buckfast bees have shown resistance to tracheal mites and can replace more susceptible strains of bees.
Proper Apiary Location
There is evidence of higher mortality rates in treacle mites in warmer conditions. As such, hives should not be placed under shade as cooler temperatures encourage mite growth.
It is imperative to maintain hygiene in beehives. This is important to rid the colony of dead bees and other pests that might be present. Cleaning also allows beekeepers to closely examine the bees and any anomalies detected early on, and take proper action as soon as possible.
2. Using Miticides (Chemical Methods)
Chemical or pesticide use for tracheal mite treatment requires approval by the Food and Drug Administration (FAD). States also impose their regulations and it is, therefore, prudent to contact the relevant department in every State before embarking on the use of chemicals to control the tracheal mite.
Chemical treatment for tracheal mites includes the use of menthol crystals, formic acid, and various miticides. In Europe, various brands of acaricides have been tested and approved for use on tracheal mites.
Chemicals containing organic formic acid as the active ingredient have been approved for tracheal mite control in the USA. Apicure™ and Mite Away II™ are formic acid-based chemicals that are registered for use on tracheal mites.
Formic acid is highly caustic and difficult to administer. Some states do not approve of formic acid and its various brands used in treating tracheal mites. Beekeepers are advised to liaise with the relevant department in their state and strive to gain some experience before they can use it for their apiaries. Once ready, it is imperative to follow the direction of use as stipulated by the manufacturers.
Apicure™ Formic Acid Gel
This is a slow-release formulation of 65 percent formic acid in gel form enclosed in a plastic pouch. It is recommended as a control measure against tracheal mites as well as Varroa mites. Apicure should only be used when there is no surplus honey flow. It is a gel that sublimes to release the active ingredient as a vapor, day-time temperatures should range from 7 °C (45 °F) to 32 °C (95 °F). At lower temperatures, sublimation may not occur, while at higher temperatures, there may be excess fumes that will suffocate the bees.
It is important to follow the label directions precisely because of the risks involved in handling the formic acid gel. For single-story hives, one Apicure™ gel plastic pouch should be slit to expose the chemical and then placed on the top bars of the frame for three weeks, after which it is removed and discarded. Where the colony is double-storied, the same procedure should be repeated. However, this time the pouch is placed on the top bars of the top story.
Miteaway II™ is another brand based on formic acid and is used in the control of tracheal mites, preferably during the fall.
Sulfur in dust form or as fumes are lethal to many species of mites when they come in contact with it. It has been used as a fumigant in the control of many external pests afflicting honey bees in some parts of the world.
Powdered sulfur is sprinkled onto bees to kill external pests. Sulphur powder is burned in a smoker and the sulphur fumes spread into the hive. There is evidence of a reduction in external pests when hives are fumigated but the effect on treating tracheal mites is unclear.
Fumigation using sulfur should be done when the bees have settled. The hive is closed at one end and fumigation is done for twenty minutes. It is thought that the action of mites is due to sulfur dioxide. However, sulfur sublimes due to the high temperatures in the smoker. Sulfur particles from sublimation will have a chance of coming into contact with tracheal mites when they are inhaled during fumigation.
3. Using Essential Oils (Wintergreen Oil-Methyl Salicylate)
Both field and laboratory tests have shown that some essential oils have antimicrobial, antifungal, insecticidal, and miticidal effects on various pest and disease-causing germs. Some of these essential oils have been used in treating honey bee diseases and pests, including infestations of tracheal mites. There is evidence that the use of essential oils can be effective up to 50-95% for some pests and pathogens.
The oil of the wintergreen plant, which is methyl salicylate is very effective against tracheal mites and has been in used for many years to control the mites. Thyme oil is particularly used on Varroa mites, but it is also effective on tracheal mites. Oil of eucalyptus has also been tried with varying results.
Application via Grease Patties
Essential oils can be delivered to colonies as part of the ingredients in grease patties. When patties are being prepared, essential oils can be added to the mixture in appropriate proportions. For instance, 3 tablespoons (1.5 ounces) of wintergreen oil (Methyl Salicylate) are added to the sugar-shortening mixture to make the wintergreen oil medicated grease patty. Lemon oil medicated grease party can also be made by adding 3 tablespoons of lemon oil to the shortening sugar mixture. It is recommended that one piece of (4 Oz) patty be placed on the top bars at the center of the brood nest. This is the position where most bees are likely to make contact with the grease patty.
Grease patties containing essential oils, and other medicaments, should be kept in the hives throughout the winter and any season when honey collection for human consumption is not taking place. They must be removed at least six weeks before expected honey flows. Note that whenever they are in use, any honey from such colonies cannot be used for human consumption.
Application via Fumigation
Essential oils can also be delivered to colonies through slow fumigation where they are made into a gel that sublimes, giving off fumes. Once the bees breathe in the fumes, internal pests such as tracheal mites come into contact with the active ingredient. Slow fumigation is the primary way of delivering menthol to colonies.
4. Using Menthol
Menthol is crystalline alcohol with fumigant action that kills tracheal mites. It is extracted from the mint plant (Mentha Arvens) and therefore, is a natural alternative to chemical miticides. Menthol is registered for use in the US and Canada. It works as a fumigant by releasing a vapor filling the hive.
The mites are killed when infected bees breathe the vapor mixed with air. The vapor does not affect the eggs and larva of the tracheal mite, only killing the adults. As such, it should be applied for a period covering the entire development time for the parasite (14 days). The effectiveness of menthol is temperature-dependent and care must be taken to ensure the correct placement of the menthol crystals as dictated by the environmental temperature.
Menthol for use in tracheal mite control is sold in pre-packaged bags, each containing 50 grams (1.8 Oz) of menthol crystals. A single packet, enclosed in porous material such as a plastic screen bag, should be placed on the top bars of the brood chamber (towards the rear end) and left in place for 20-25 days. Daytime temperatures should range between 15 °C (59 °F) and 26 °C (79 °F) as menthol vapor is effective only at these temperatures. During hotter daytime temperatures (exceeding 26 °C / 80 °F), the menthol packet should be placed on the bottom board of the hive.
Beekeepers must ensure that there are no honey supers during the treatment and the menthol packet must be removed at least one month before any anticipated honey flow.
Apart from the menthol crystals, various brands of menthol, including Mite-A-Thol™ are available for use in treating tracheal mites. In temperatures below 15 °C (59 °F), a Mite-A-Thol™ packet should be placed on top of the frames while in temperatures above 26 °C (79 °F), the Mite-A-Thol™ packet should be placed on the bottom board.
Essential oils such as oil of wintergreen, thymol, menthol, or eucalyptus, however, cannot be used alone in the control of tracheal mites because of their inconsistency and unreliability. Their effectiveness is dependent on a lot of factors including time of the year, bee populations, and temperature. This means that they cannot be used alone but should be used as part of an integrated pest control program as natural alternatives to pesticides.
Making Tracheal Mite Grease Patties
Grease patties, a homogeneous mixture of hydrogenated vegetable oils and sugar, have been found effective mainly by inhibiting the ability of tracheal mites to transfer from one bee to another. Grease patties are thus a good control measure for tracheal mites. Their effectiveness is enhanced when certain essential oils that are effective against the mite are added.
The patty is prepared by mixing shortening and sugar at the ratio of one part shortening and two parts granulated sugar. If vegetable oil is used, then the ratio is one part by weight of vegetable oil to three parts of granulated sugar
For delivery of this mixture into the hives, pieces of grease patty, each measuring about 100mm in diameter and about 9mm thick are prepared and sandwiched between wax paper for storage before they are placed in the beehives. One piece is placed centrally on the top bars of the frames within the brood box for each hive. Bees will come into contact with patties as they go about their work in the hive. All hives nearby should be given the treatment to reduce the risk of cross-infection.
Grease patties contain no active chemical ingredient and thus are suitable for use throughout the year, though it is preferable to use them during early spring and during the fall when flows are absent. Like for other treatments, patties should be removed from the hive at least six weeks before honey flow begins.
Does Apivar Treat Tracheal Mites?
Apivar is an Amitraz-based mite control product. Strips of Apivar made of a rigid plastic polymer, continuously release the active agent slowly into the hive for several weeks before they are withdrawn. Apivar is a very effective control measure against Varroa mites, with a single application getting rid of 99% of Varroa mites in a colony if applied properly.
Despite its effectiveness on Varroa mites, however, Apivar does not affect tracheal mites. There is no evidence that it has any effect on this pest whatsoever. Apivar should, therefore, never be used to treat tracheal mites.
It is important to note that some medications on Varroa mites do have some effect on tracheal mites but this is never indicated on the label directions because they are primarily registered for use on the former. For instance, Apiguard, (the active ingredient is thymol, an essential oil extracted from the thyme plant) is primarily made for use in controlling Varroa mites, but it is also very effective against the tracheal mite. Thus, caution must be taken to avoid using preparations recommended for controlling Varroa mites on tracheal mites.
Caution on the Use of Chemicals in Controlling Tracheal Mites
To protect people and the environment, pesticides should be used safely. The Food and Drug Administration and state governments have imposed strict regulations on the handling, storage application, and disposal of pesticides. Manufacturers have also laid down directions on the dosage, mode of application, disposal, and timing of the application for every one of their brands which, by law, must be followed to the letter.
Read and follow label directions carefully before you buy, mix, apply, store, or dispose of any pesticide. It is also advisable to seek advice from registered veterinarians on the use of pesticides. Some of these pesticides require recommendations before they can be purchased. According to laws regulating pesticides, they must be used only as directed on the label.
Preventative Measures Against Tracheal Mites
The first line of defense against infestation is to take preventive measures, as the mites have proved hard to eradicate once an attack occurs. It is recommended that apiaries should adopt resistant bee varieties and desist from practices that predispose uninfected colonies to attack. Selective bee breeding is the first measure that beekeepers should employ to counteract tracheal mites. Buckfast bees, for example, are known to be highly resistant to this mite, while New Zealand strains are very susceptible. Hive hygiene should also become a priority for both beginner and experienced beekeepers.
Menthol crystals and formic acid have been used in North America with considerable success in reducing tracheal mite infestation in colonies. It is noteworthy that it is only menthol that is presently FDA-approved for use in controlling tracheal mites in the USA, though other miticides are available.
Several brands of pesticides based on menthol and formic acid have been developed to control the mite. Top among them is Apicure™, a formic acid-based brand) and Mite-A-Thol™, a Menthol-based brand.
Other controls such as using essential oils (wintergreen oil) have shown considerable success in Europe and Oceania. For instance, Apiguard, a thymol-based preparation has been shown to work well in several countries in controlling tracheal mite numbers.
In the use of substances to control tracheal mites, directions by manufacturers must be followed, as should the rules and regulations imposed on chemical usage by the FDA and other regulatory bodies, be they state or federal.
Both beginner and experienced beekeepers can know these regulations and how to best meet them in beekeeping clubs. Agricultural authorities near them are also reliable sources of information. Seminars, workshops, and other training that is relevant to beekeeping are also recommended.
This is chiefly to reduce the risks posed by the substances to the users, the bee colonies, and the environment in general. Tracheal mite disease could be brought under control if it is detected early and control measures are executed as per the laid down guidelines and regulations. Successfully treating tracheal mites (Acarapis Woodi) in bees is possible for beekeepers and can be done without too much of a negative impact on your beekeeping operation.
Have you ever dealt with a Tracheal mite infestation in your beehives? Leave a comment below and let us know what your experience was like.