The Bee Bench › Disease & Pest ID
Search by what you're looking at on the frame. Ten of the things most likely to be wrong, what each one looks like, and what to do about it.
Mite and virus complex
What you see: Spotty brood, perforated or chewed-down cappings, twisted larvae. White guanine crystals on the ceilings of brood cells. Deformed wings and K-wing on adults. Reddish-brown mites visible on bees or in drone brood.
What to do: Monitor with an alcohol wash or sugar roll and treat when you're over threshold. This is the number one colony killer in North America — nearly every winter loss traces back to it somewhere.
Bacteria — Paenibacillus larvae
What you see: Sunken, greasy, perforated cappings. Brown, goopy pupae that rope out 2 cm or more on a toothpick. Hard black scale stuck down in the cell that will not scrape off. A distinct foul smell.
What to do: Highly infectious and very serious. Do not share equipment or move frames. Send a sample to the Beltsville Bee Lab — it's free — and contact the Pennsylvania state apiarist. Confirmed cases usually mean burning the infected equipment.
Bacteria — Melissococcus plutonius
What you see: Twisted, melted-looking larvae that turn brown or yellow and die BEFORE the cell is capped. Goopy, but ropes far less than AFB — about 1.5 cm at most. Often a sour smell rather than a foul one.
What to do: Often clears on its own with a strong nectar flow, requeening, or comb rotation. The important job is telling it apart from AFB — when you are not certain, send a sample.
Fungus — Ascosphaera apis
What you see: Larvae turn into hard, chalky white mummies, sometimes spotted black or blue. They rattle in the cells and show up on the bottom board or scattered at the entrance. Scrape out easily and never rope.
What to do: Usually a stress symptom rather than a disease problem in itself. Improve ventilation, requeen with hygienic stock, and keep the colony strong.
Virus
What you see: Fluid-filled, sac-like larvae lying flat in the cell. They turn brown and settle to the bottom, head dark and curled up — the classic Chinese-slipper or canoe shape.
What to do: Usually self-limiting in a strong colony. Requeen if it persists across several brood cycles.
Gut fungus — N. apis / N. ceranae
What you see: Dysentery — brown streaking on and around the hive, especially with N. apis. Crawling bees that cannot fly, a shrinking adult population, a colony that dwindles away without an obvious cause.
What to do: Reduce stress, improve ventilation, replace old comb. A spore count confirms it if you want certainty.
Mite — Acarapis woodi
What you see: K-wing, where wings are held out at odd angles. Crawling bees that cannot fly. Discolored tracheae, but you need magnification to see that.
What to do: Much less common than it once was. Grease patties and resistant stock both help.
Pest — Galleria / Achroia
What you see: Silk webbing and tunnels running through comb, worst in weak colonies and in stored comb. Larvae burrow under cappings, leaving bald-brood trails.
What to do: Almost always a symptom rather than a cause — a strong colony handles wax moths itself. Strengthen or combine the colony, and protect stored comb by freezing the frames and keeping them cool and airy.
Pest — Aethina tumida
What you see: Small, fast black beetles running for cover when you lift a frame. Slimy, fermented-smelling comb. Larvae tunnelling through the honey.
What to do: Keep colonies strong and reduce open space they can't patrol. Beetle traps help. Much worse in warm, humid weather and in a hive with more room than bees.
Virus — vectored by varroa
What you see: Adults emerging with crumpled, stubby, useless wings. Bloated abdomens. Badly shortened lifespan.
What to do: A red flag that your mite load is high, not a separate problem to treat. Get the mites under control — the virus rides in with them.