Adult bee diseases mostly run a silent course. Unlike brood diseases they give no distinct picture; the colony simply weakens.

Diagnosis therefore depends on the whole picture rather than any single sign.

The main agents

• Nosema: A microsporidian affecting the gut. Two species occur, with different pictures
• Viruses: Deformed Wing Virus above all; most become active in association with Varroa
• Amoeba: Affects the Malpighian tubules; usually found together with nosema
• Septicaemia: Bacterial multiplication in the haemolymph; associated with damp conditions
• Tracheal mite: A microscopic mite living in the breathing tubes

Common signs

• Bees crawling in front of the hive, unable to fly
• Trembling and loss of coordination
• Unexplained weakening of the colony
• A drop in foraging force
• Failure to overwinter

The signs overlap heavily. A few findings are distinguishing:

• Faecal marks → suggests Nosema apis
• Hairless, shiny black bees → chronic bee paralysis
• Segments separating easily → septicaemia
• Deformed wings → viral load driven by Varroa

The common cause: Varroa

Most adult bee diseases run a more severe course in a colony under mite pressure. The mite does direct harm, transmits viruses and suppresses immunity.

The foundation of adult bee health is therefore Varroa management.

Common measures

• Keep Varroa under control
• Renew comb regularly. Spores and agents accumulate in old comb
• Reduce moisture inside the hive
• Keep nutrition strong. Varied pollen increases resistance
• Provide clean water
• Do not buy colonies from unknown sources
• Requeen where a colony weakens persistently

Diagnosis

Most adult bee diseases require microscopy or laboratory analysis for definitive diagnosis. A sample of about thirty bees is enough for most examinations.