Diagnostic Aid

Nosema and Tracheal Mites

Nosema spores on hemocytometer grid (400x magnification). Photo by Dr. Zachary Huang
Nosema spores on hemocytometer grid (400x magnification). Photo by Dr. Zachary Huang
Tracheal mites inside a honey bee trachea. 
Photo by Simon Hinkley & Ken Walker
Tracheal mites inside a honey bee trachea.
Photo by Simon Hinkley & Ken Walker

Nosema sp. are microsporidian gut parasites that destroy the gut epithelial cells as they multiply, and this causes bees to become starved and will weaken the colony as a whole.

Tracheal mites are microscopic mites that reproduce and live in bee trachea. The presence of these mites can make it harder for the bees to breathe and atrophy muscles so they cannot fly. Tracheal mites are not as concerning as they once were since many beekeepers utilize miticides to keep Varroa mites under control.

Both of these parasites can cause symptoms that are not unique and could be indicative of a handful of stressors.

Microscopy is the only way to confirm diagnosis of either of these in honey bees!

Below, you can find a seminar covering a deep-dive in to these two parasites, and how to diagnose infection in your honey bees. There is also a supplemental demonstration for how to count Nosema spores in your honey bees, using household materials such as a Ziploc bag and rolling pin.

This Diagnostic Microscopy Seminar covers information about:

  • Difference between stereo/dissection and compound microscopes
  • Proper handling and how to use microscopes
  • Nosema biology, symptoms, impact, & treatment
  • How to use a hemocytometer and quantify Nosema infection
  • Tracheal mite biology, symptoms, impact, & treatment
  • How to dissect honey bees to observe tracheal mite infestation

video coming soon

This training shows how to quantify Nosema infection in your honey bees!

Click here to watch the Spanish version.


Looking for a diagnostic lab to submit bee samples to?

WSU Bee Program does not currently offer a diagnostic service, we recommend that beekeepers send samples to the Bee Research Laboratory in Beltsville Maryland.

This a free service.

How to Send Adult Honey Bees
  • Send at least 100 bees and if possible, select bees that are dying or that died recently. Decayed bees are not satisfactory for examination.
  • Bees should be placed in and soaked with 70% ethyl, methyl, or isopropyl alcohol as soon as possible after collection, and packed in leak-proof containers.
  • USPS, UPS, and FedEx do not accept shipments containing alcohol. Just prior to mailing samples, pour off all excess alcohol to meet shipping requirements.
  • Do NOT send bees dry (without alcohol).
How to Send Brood Samples
  • A comb sample should be at least 2 x 2 inches and contain as much of the dead or discolored brood as possible. NO HONEY SHOULD BE PRESENT IN THE SAMPLE.
  • The comb can be sent in a paper bag or loosely wrapped in a paper towel, newspaper, etc. and sent in a heavy cardboard box. AVOID wrappings such as plastic, aluminum foil, waxed paper, tin, glass, etc. because they promote decomposition and the growth of mold.
  • If a comb cannot be sent, the probe used to examine a diseased larva in the cell may contain enough material for tests. The probe can be wrapped in paper and sent to the laboratory in an envelope.

Include a short description of the problem along with your name, address, phone number and/or e-mail address.

Bee Disease Diagnosis Bee Research Laboratory
10300 Baltimore Avenue BARC-East
Bldg. 306 Room 316
Beltsville Agricultural Research Center – East
Beltsville, MD 20705

They do not analyze samples (bees, wax comb, pollen, etc.) for the presence of viruses or pesticide residues.*

*Options for diagnosing viral infections are limited. Some viruses cause clear symptoms that can be used to diagnose their presence. For identification of infections in colonies that do not show symptoms, evaluation of prevalence or levels of viruses require molecular approaches, such as polymerase chain reaction (PCR). This service is not usually available to the general public.

*Options for confirming if your bees died from pesticide poisoning is often expensive and challenging if you do not know what chemical(s) they were exposed to. If you feel that the symptoms you are seeing with your bee die offs are due to pesticide exposure instead of starvation or a viral disease, you can confirm it by sending bee samples to a place in Portland, OR called Synergistic Pesticide Lab(linked) or other pesticide testing facilities. 

Pesticides often cause sub-lethal effects to bees such as shaking, trembling, or tongue sticking out. Some of those symptoms are also symptoms of viral infections. Remember that die offs from pesticide poisoning usually involve a large number of bees, of the same age, dead in front of your hive(s). Please report a mass die off to Katie Buckley (Washington Department of Agriculture) kbuckley@agr.wa.gov to investigate.

Here is a website with other diagnostic labs in the U.S. if interested.