bee-keeperHealthy bees are rarely sick — trouble usually starts when a colony is weakened, overrun by varroa mites, or exposed to poor conditions. That is why the fight against disease is won not with medicines but with good beekeeping: strong colonies, clean equipment, and regular inspection. This guide helps you spot the most common diseases and pests in time, and know when a situation is serious.
A strong colony is the best defence
Most bee diseases are not cured but prevented. A strong colony with a young queen, enough food, and varroa under control handles most pathogens on its own. Hygiene is decisive — never move comb or tools from a sick colony into a healthy one, replace old dark comb regularly (renewing about a third of the comb each year is a good rule), and never leave honey or comb out to be robbed.
Quarantine for new bees is smart too: keep purchased colonies, swarms, and second-hand equipment apart and inspect them before adding them to your apiary.
American foulbrood — the most dangerous
American foulbrood (AFB) is a bacterial disease of capped brood and the most dangerous bee disease. The signs are sunken, dark, perforated cappings, a patchy "mosaic" brood pattern, and larvae that decay into a sticky, ropey mass — touch an infected larva with a matchstick and it stretches into a thread several centimetres long. There is often a foul smell as well.
American foulbrood is a disease you are legally REQUIRED to report to the veterinary service. The spores are extremely tough and survive for years in comb and equipment. Do not move hives, do not lend tools, and call the vet immediately — the usual measure is burning the infected colonies and equipment to stop the spread.
European foulbrood
European foulbrood (EFB) also attacks brood, but usually open (uncapped) brood. The larvae change colour from pearly white to yellow and brown, twist in their cells, and die before capping. It is less lethal than AFB but also notifiable and warrants a vet consultation. Strong colonies and good nutrition help a colony recover.
Nosema
Nosema is a disease of adult bees caused by a microsporidian in the gut. It weakens the colony, shortens bees’ lives, and cuts the yield, and often shows as dysentery (faecal spotting on the front of the hive) and a slow spring build-up. A dry, damp-free hive, requeening, good winter stores, and avoiding stress all help. The best prevention is a strong, well-wintered colony.
Chalkbrood (ascosphaerosis)
Chalkbrood is a fungal disease in which larvae die and harden into white or grey "mummies" like little chalky lumps — you often find them on the floor or in front of the entrance because the bees throw them out. It appears in damp, weak, or chilled colonies. It is rarely fatal on its own; you fix it by strengthening the colony, a drier site, and requeening with a more resistant line.
Pests: wax moth, mice, hornets
Besides diseases, colonies are attacked by pests:
- Wax moth — a moth whose larvae tunnel through comb and turn it to webbing; it mainly hits weak colonies and poorly stored drawn comb
- Mice — they enter the hive in autumn and winter, build nests, and disturb the cluster; keep them out with a reduced entrance or a metal guard
- Hornets and wasps — they catch bees at the entrance and can rob a weak colony in late summer
- Ants — more a nuisance than a real threat, but they will steal feed from feeders
The best protection against all of them is, again, a strong colony and a tidy apiary.
When you must call the vet
The golden rule: if you suspect American or European foulbrood — do not move hives, do not lend equipment, and call the responsible veterinary service immediately. These diseases are legally notifiable, and early detection protects both your apiary and your neighbours’. Never "treat blind" with antibiotics — it masks the symptoms, leaves residues in the honey, and makes diagnosis harder.
Record the signs in time
Diseases are easiest to stop when you catch them early, and that means tracking each colony over time. In the bee-keeper app you keep an inspection log for every hive — brood condition, suspicious signs, measures taken, and dates — so you can easily see which colony is weakening and act before it is too late.