Apiculture Factsheet #219
Tracheal Mites in Honeybee
Colonies
The Honeybee Tracheal Mite (HBTM) was first introduced into
Canada in the late 1980s and has since spread to most of Canada’s
beekeeping areas. This microscopic mite called Acarapis woodi,
parasitizes adult bees causing the weakening of the colony and
increased winter mortality.
Field Diagnosis
- Disease caused by tracheal mites is called Acarine disease, or
Acariosis, named after its scientific name Acarapis woodi
Oudemans.
- Tracheal mites can’t be seen with the naked eye. Confirmation
of infestation requires microscopic examination.
- Infected colonies are most likely to show signs of infestation
in spring and fall when mite populations reach their peak.
- In cases of severe infestation, large numbers of adult bees
crawl in front of the hive incapable of flight and coordination.
Many adults extend their wings outward, often described as
“K-Wing”.
- Infected adult bees may be lethargic. Even on good days, a
high proportion of bees are in the hive instead of flying.
- Colonies are slow in population build up in the spring and
lack vigor. In the fall, a higher than normal proportion of the
bee population dies before the onset of winter.
- Colonies show variability in their sensitivity to tracheal
mites. Some colonies are resistant and unaffected by tracheal
mites, while other colonies may be severely affected and collapse.
- Since the mite introduction, many beekeepers have selected for
tracheal mite resistance and in general, the disease is no longer
considered serious.
Collection of Bee Sample
- Randomly selected adult bees can be collected in the apiary
and placed in alcohol water solution (50%). In case ethanol or
rubbing alcohol (propanol) is not available, bees can be
temporarily placed in windshield wiper fluid containing methanol.
- Tracheal mite infestations in an apiary are often un-equally
distributed. Typically, there are “hot spot” infestations. For
this reason, each colony in the apiary must contribute equally to
the bee sample being collected.
- A sample of bees from an apiary, regardless of the number of
colonies, must contain at least 75 bees in order to detect a
general tracheal mite infestation of 2.5 % or higher in the
apiary, at 95% confidence (= 19 times out of 20).
Laboratory Diagnosis
- Acarapis woodi is an obligate, endo-parasitic mite
affecting the trachea or breathing tubes of the thorax of adult
honeybees.
- Using a dissecting microscope in the laboratory, adult bees
are placed on their back, decapitated and the frontal section
(collar) of the thorax is removed with a surgical blade or pulled
with fine forceps. The major tracheae are exposed and can be
examined.
- Healthy, non-infected tracheae appear milky-white in color and
almost transparent. Infected tracheae are mottled, sometimes
bronzed in appearance, and with darkened patches. Higher
magnification sometimes allows for the identification of adult
mites.
- Light infestation generally involves one tracheal tube
affected by mites (mono-lateral) while heavy infestation involves
the damaged tissue of both tracheal tubes (bi-lateral).
- Since bees originated from different colonies, the testing
results only reflect the condition of the apiary. Reading of these
composite samples can only describe low or high infestations or
“an apparent absence”.
Control and Treatment
- Before applying chemical controls, closely examine the
colonies for signs of HBTM infection. Look for adult bees crawling
in front of the hive, lack of vigor, display of K-Wing.
- When symptoms have been noted, a chemical control may be
applied without having to collect bee sample for laboratory
analysis first. Lab analysis is slow, labor intensive and
expensive.
- In Canada, menthol and formic acid have been registered for
control of HBTM. See Factsheet #221
for application instructions.
- Apply chemicals only in spring or fall, with honey supers
removed.
- Select for tracheal mite resistant bee stock, or purchase
resistant stock from a bee breeder.
- Increased incidence and severity of infestation is worsened
when bees are stressed. Stress factors may include presence of
other diseases, poor forage availability, too many colonies placed
in one location causing interference and robbing, lack of feed and
pollen, poor beehive equipment, inclement weather, etc.
- Other preventative measures include: don’t collect swarms
whose origins are unknown; reduce movement of colonies and avoid
high density areas; don’t introduce colonies from infected areas
or colonies that have not been tested into the beekeeping operation.
03/12
