In most countries no generally available approved product exists for nosema. The approach targets conditions.

Why there is little to treat

The parasite lives in the gut cells of adult bees. It spreads through spores passed with the faeces that persist in the comb.

Bees cleaning the comb take up the spores. The infection therefore sits in the material, not only in the bees — and that makes comb renewal the most important measure there is.

The measures that work

• Renew comb regularly. The most effective single measure
• Reduce damp in the hive: Ventilation, a slight forward tilt, a dry site
• Watch the winter stores: Honeydew honey burdens the gut and should not be left as winter feed
• Provide varied pollen; nutrition determines resistance
• Keep Varroa under control
• Limit stress: Less opening, less moving
• Requeen persistently weak colonies
• Unite rather than drag along

The two species

There are two nosema species. One gives the classic picture with faecal marks and peaks in spring; the other often runs insidiously, without clear outward signs.

Distinguishing them requires laboratory testing, but in practice it matters little: the measures are the same.

Diagnosis

Not determinable in the field. The spores are only visible microscopically; sample older foragers, not young bees from the comb.

What not to do

Use products not approved for bees. They solve nothing and leave residues in honey and wax.

Disinfecting equipment

Comb from a heavily infected colony goes out of circulation. Hive parts can be flamed; the spores are less durable than those of foulbrood but do survive in comb.