Bee diseases and warning signs

American foulbrood (AFB)

A serious bacterial brood disease caused by Paenibacillus larvae. Long-lived spores can spread through contaminated honey and equipment. Warning signs include irregular brood, sunken or perforated cappings, brown larval remains and tightly attached scales. Smell alone is not a reliable test.

What to do next

Stop transferring suspect frames, bees or honey to other colonies. Prevent robbing and seek prompt diagnostic guidance. Confirmed AFB requires an appropriate containment and equipment plan with qualified help and applicable state requirements. Antibiotics do not eliminate the spores; routine freezing is not reliable AFB decontamination.

European foulbrood (EFB)

A bacterial brood disease caused by Melissococcus plutonius, often affecting young larvae before capping. Discolored or twisted larvae and an uneven brood pattern can be clues. Confirm the cause before deciding what to do. Check the colony’s food supply, stress and equipment cleanliness too.

Chalkbrood

A fungal brood disease caused by Ascosphaera apis. Infected larvae can become hard, chalk-like “mummies.” Assess colony strength and conditions rather than assuming a mite treatment will cure it.

Sacbrood

A viral brood disease in which affected larvae may form a fluid-filled sac and later dry into scales. Identification and supportive colony management matter; it is a different condition from bacterial foulbrood.

Deformed wing virus and other viruses

Varroa can transmit viruses, including deformed wing virus. Crumpled wings, impaired movement or a dwindling population call for investigation, but many infections have no obvious external signs. Managing mites helps reduce an important route of viral damage; it does not instantly reverse damage to an already affected bee.

Nosema / Vairimorpha

These microscopic, spore-forming parasites infect adult bees and reproduce in gut cells. Infectious spores may be ingested through contaminated material. The names Nosema apis and Nosema ceranae remain common; you may also see the genus name Vairimorpha.

Fecal staining is not enough to diagnose nosema, and its absence does not rule infection out. Microscopy or laboratory testing can help clarify the problem; species identification may need molecular testing. Check the colony’s food supply and sources of stress. Ask a qualified adviser about current, approved treatment options.