Facts about Nosema
What is Nosema?
Nosema is two species of microsporidian (Nosema apis and Nosema ceranae) that infects the mid-gut of honey bees. Nosema apis has probably been in the country since bees were introduced and Nosema ceranae was recently detected in the Coromandel (Ministry of Primary Industries) and is displacing Nosema apis in New Zealand as it has in other parts of the world.
Nosema spp. is a spore forming parasite. Once an individual adult bee is infected, these microsporidians grow and multiply in the bees’ gut, hampering absorption of nutrients. The spread of Nosema spp. is exponential within the hive.
Why does Nosema kill hives?
Adult bees that are infected with Nosema spp. live shorter lives, thus affecting foraging and nurse bee behaviours in the hive. They are weaker, which makes them less effective at foraging for pollen and honey. Queens infected with Nosema spp. slow or stop egg laying, and may induce supersedure and die. The bees with Nosema are sick and will defecate in the hive rather than leave. As the house bees clean up they become infected and the cycle begin again.
What are the visible clues of Nosema?
Nosema is difficult to detect from visual inspection. There are few if any signs that a beekeeper can pick up on until the infection rate has reached a very high level. Some signs that MAY be seen are:
• Bees crawling outside the hive due to weakness,
• Fecal matter spotting on combs and at bottom board on entrance because the bees are too weak to leave the hive,
• Poor laying pattern if the queen is infected (not to be confused with AFB),
• General failure to thrive despite plenty of bees being visible in and around the hive.
In many cases the hive will look just fine until shortly before it fails.
Managing Nosema
In North Amercia and Europe, bees are fed an antibiotic to control Nosema spp. In NZ we have made the decision to not use any antibiotics for Nosema spp. or AFB. Options to address infections are:
• Move the hive to warmer, sunnier spot with good cold air drainage.
• Remove and replace brood combs older than 3 years. If the comb is dark or black it is considered old. Beekeepers should rotate their comb within the brood box as well as removing and replacing old comb. If you are using PLASTIC frames they will not discolour like wooden frames do, and an age marking system should be used to indicate when to remove them to prevent Nosema build-up.
• Re-queening hives can bring sufficient vigour into hive to overcome an infection.
• Improve bee keeper hygiene by cleaning and sterilizing bee gear between hives. This also helps reduce the spread of AFB.
• Redesign or adapt beekeeping equipment to provide a warmer drier internal environment.
• Remove and replace brood combs older than 3 years. If the comb is dark or black it is considered old. Beekeepers should rotate their comb within the brood box as well as removing and replacing old comb. If you are using PLASTIC frames they will not discolour like wooden frames do, and an age marking system should be used to indicate when to remove them to prevent Nosema build-up.
• Re-queening hives can bring sufficient vigour into hive to overcome an infection.
• Improve bee keeper hygiene by cleaning and sterilizing bee gear between hives. This also helps reduce the spread of AFB.
• Redesign or adapt beekeeping equipment to provide a warmer drier internal environment.