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Honey Bee Diseases and Parasites

by Korhan Kaftanoglu

Updated October 2026. Like us, honey bees have many diseases and parasites that affect how colonies survive and grow. Bee diseases fall into two groups: brood diseases and adult bee diseases.

Common brood diseases

  • American foulbrood (AFB): bacterial disease (Paenibacillus larvae)
  • European foulbrood (EFB): bacterial disease (Melissococcus plutonius; secondary bacteria include Paenibacillus alvei and Enterococcus faecalis)
  • Chalkbrood: fungal disease (Ascosphaera apis)
  • Stonebrood: fungal disease (Aspergillus fungi, mainly A. flavus and A. fumigatus)
  • Sacbrood: viral disease (sacbrood virus)

Common adult bee diseases

  • Nosema: microsporidian disease (Vairimorpha apis and Vairimorpha ceranae, formerly called Nosema)
  • Septicemia: bacterial disease (Pseudomonas aeruginosa)
  • Chronic bee paralysis: viral disease (chronic bee paralysis virus)
  • Acute bee paralysis: viral disease (acute bee paralysis virus)
  • Deformed wing virus: viral disease, spread mainly by Varroa mites

Common parasites

Common pests

Honey bee diseases and parasites, especially the brood diseases and the Varroa mite, are the biggest problem in beekeeping worldwide. Governments and beekeepers both have a responsibility to keep them from spreading.

The federal Honeybee Act of 1922 restricted the import of live adult honey bees into the US, and all 50 states have their own laws on bee diseases, registration, parasitic mites and Africanized honey bees.

Beekeepers' responsibilities

However many colonies you keep, you need a disease management plan.

First, learn to recognize bee diseases and parasites. If you don't know the symptoms, you can't act in time, and you may lose your colonies and spread the pathogens in your area.

Second, inspect your colonies regularly. We recommend every 10 days in states with Africanized bees and every 2-3 weeks elsewhere. Know how strong each colony is and what condition it's in. Experienced beekeepers can often spot a problem just by watching the flight activity at the entrances.

  • If flight activity looks unusual, check that colony first.
  • Many dead bees in front of a hive can point to a pesticide kill or robbing.
  • In a robbed colony, hundreds of bees try to get in through the entrance, between the boxes and anywhere else they can. The hive bees fight the robbers, and you'll see many dead bees in front of the hive. There are often wax bits on the landing board, and the entrance and the joints between boxes look darker where the robbers went in. Learn to tell robbing from normal flight.
  • Lift the back of each hive to check its weight. A light hive may be short of honey, or the colony may have starved, been robbed or absconded.
  • Check the abnormal-looking colonies first. If a colony is dead or has been robbed, remove the hive from the apiary, clean it, and reuse the combs if they're healthy. If there's a disease, deal with it before it spreads.

During each inspection, check for the queen first

Look at how the queen is performing:

  • A good brood pattern with eggs and larvae means the queen is present.
  • No eggs or open brood, plus queen cells, means the queen has died or been killed and the colony is raising a new one.
  • Emerged queen cells and no open brood usually means there's a virgin queen in the hive.
  • No worker brood, many small drones and several eggs per cell means the colony has been queenless a long time and has laying workers. If a laying-worker colony is very small, shake out the bees and give the combs to other colonies. If it's still strong, give it a frame of eggs and young brood so it can raise a new queen.

For more, see what to do in a queenless hive.

Questions to ask about the brood

  • Are there eggs, larvae and pupae? If yes, the queen is present.
  • Is the brood pattern solid? If yes, the queen is young, productive and in good shape.
  • Does the brood look healthy? Sealed brood should have an even, healthy color.
  • Are the cappings sunken, dark, greasy-looking or punctured? This can be a sign of American foulbrood (AFB). Holes in cappings can also come from hygienic bees uncapping sick brood or from chalkbrood, so look for the other AFB signs too.
  • Are any larvae in open cells yellow, brown or black? This can be a sign of European foulbrood (EFB).
  • Is there an unusual smell, like rotten meat or sour wood glue? This can point to AFB and/or EFB.

Questions to ask about the adult bees

  • Are there workers or drones with missing or deformed wings? This points to a serious Varroa mite problem, and the colony may be hard to save.
  • Are there beetles or beetle larvae in the corners or on the bottom board, or slimy, fermenting honey? This points to a serious small hive beetle problem.
  • Are there brown fecal streaks inside or outside the hive and around the entrance? This is dysentery. It can be linked to Nosema, but it can also come from long confinement or poor-quality winter food.
  • Are the bees clustered and unable to move or fly? They're starving and will die soon. Give them one or two frames of honey right away and start feeding. Scratching open the honey cappings with a hive tool or uncapping fork helps the bees reach it.

When to call your state apiary inspector

If you see signs of American foulbrood or anything you can't identify, contact your state apiary inspector before treating or moving any combs or equipment. Each disease needs its own corrective action, and some, like AFB, are regulated by law.

More in this series: American foulbrood (AFB) · European foulbrood (EFB)

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