Colony Hygiene

Colony hygiene is the set of practices that prevent disease agents building up and spreading in a honey bee colony, covering both the bees' own cleaning behaviour and the beekeeper's cleaning of hives, combs and tools. Most diseases are prevented not with medicines but with these cheap, regular habits.

Why does colony hygiene matter?

A hive is a warm, humid environment in which thousands of bees live in a confined space. Foulbroods, chalkbrood, nosema and viruses spread in this environment through combs, honey, tools and the bees themselves. Colony hygiene has two sides, and they complement each other:

• The bees' hygiene: Finding diseased or dead brood and throwing it out, cleaning the hive and coating it with propolis.
• The beekeeper's hygiene: Comb replacement, tool cleaning, care when moving frames, hive maintenance and correct handling of dead colonies.

What is hygienic behaviour in bees?

Hygienic behaviour is when worker bees detect diseased, dead or mite-infested brood in sealed cells, uncap the cells and remove the brood. This behaviour is heritable; some colonies do it very quickly and thoroughly, others not at all.

Colonies with strong hygienic behaviour:

• are more resistant to chalkbrood and the foulbroods; they clear out diseased brood before the agent spreads.
• partly limit varroa reproduction; they remove some of the mite-infested brood.
• make the beekeeper's job easier by clearing up problems early and on their own.

How is hygienic behaviour measured?

The common method used by breeders is the freeze-killed brood test: a piece of comb with capped brood is cut out and frozen to kill the brood, then returned to the hive. After a set time (commonly 24 hours), the proportion of dead brood the bees have removed is counted. Colonies that clear almost all the dead brood in that time are considered hygienic and are preferred for queen rearing. The same test can also be done by killing the brood with a fine pin.

Comb replacement: the most effective hygiene measure

Old comb accumulates three things: disease agents (bacterial and fungal spores), chemical residues (residues of treatments and pesticides build up in wax) and cocoon remains (cells shrink and bees get smaller). Replacing about a third of the brood combs every year is the most effective hygiene measure a beekeeper can take.

• Dark combs that let no light through when held up to it are removed first.
• Removed combs go for wax rendering; having foundation made from your own clean cappings wax breaks the residue cycle.
• In badly affected colonies, shaking all the bees into a new hive onto foundation (the shook swarm method) renews both the combs and the disease load in one go.

Disease is often carried by the beekeeper

Bees carry disease between hives through drifting and robbing; but the fastest and furthest-reaching carrier is often the beekeeper.

• Hive tool: The most common route of infection from hive to hive. American foulbrood spores stay viable on the tool's surface for a long time and are not killed by alcohol. Scrape honey and propolis off the tool, wash it in a hot washing soda solution or pass it through a flame. Working with several hive tools and cleaning them in turn is a practical solution.
• Gloves: Leather gloves cannot be cleaned properly; disposable or washable gloves are more hygienic. Change gloves after a suspect colony.
• Moving frames and honey: Passing frames around between colonies at random is the riskiest practice. Don't give frames, honey or pollen from a colony you are not sure is disease-free.
• Moving between apiaries: When visiting other apiaries, take your equipment there clean and bring it back clean.

Inside the hive and around the apiary

• Match the space to colony strength: Empty comb that the bees cannot cover and defend is an invitation to wax moth and other pests.
• Control damp: Raise the hive off the ground, tilt it slightly forward and provide top ventilation if needed. Mould and chalkbrood increase in a damp hive.
• Read the floor debris: The debris that collects on the hive floor (wax fragments, pollen, dead mites, mummies) tells you about the colony's condition. Scrape the floor clean in spring.
• Seal cracks in the hive: Cracks and holes lead to robbing, pests and heat loss.
• Reduce drifting: Arranging hives in groups rather than one long row, facing different directions or painted different colours, reduces bees entering the wrong hive and carrying disease.
• Provide clean water: A clean water source near the apiary stops the bees going to dirty, stagnant water.

Wax moth and hive pests

Strong, populous colonies clear out wax moth larvae that get into the hive themselves. The problem starts in empty combs the bees can't cover and in combs kept in storage. Keeping the colony in a space suited to its strength and protecting stored combs is the best defence against wax moth.

New colonies and material brought in from outside

Colonies, swarms, combs and honey from outside are the easiest way for disease to get into an apiary.

1. If possible, keep a new colony under observation at a separate site for a few weeks.
2. Check the brood, look for signs of chalkbrood and foulbrood, and check the mite level.
3. Don't feed honey or pollen of unknown origin; be very careful when buying second-hand hives and combs.

What should you do when you find a dead colony?

When a colony is found collapsed or dead, the hive must be closed immediately and made bee-proof. A hive left open gets robbed, and the disease agent inside spreads with the honey through the whole apiary and even to neighbouring apiaries.

• Don't give its combs and honey to another colony until the cause of death is known.
• Try to distinguish between starvation, cold, varroa and signs of disease; if necessary, take a sample and send it to a laboratory.

Cleaning hives and equipment

• Scraping: Empty boxes, floors and frames are cleaned by scraping off propolis and wax residue.
• Scorching: The inner surfaces of wooden hives can be cleaned by passing a blowtorch flame over them (until they darken slightly). Plastic and polystyrene hives must not be scorched; clean them with the washing method the manufacturer recommends.
• Washing: Feeders, queen cages and plastic parts are washed in hot water with washing soda and rinsed.
• Records: Knowing which equipment came from which colony lets you trace the source when a problem arises.