Brood Diseases

Unlike diseases of adult bees, brood diseases can be seen on the comb: a regular, careful brood inspection catches most of them early. The most important task is to distinguish the two notifiable foulbroods (American and European) from chalkbrood, sacbrood, chilled brood and varroa damage. If you suspect foulbrood, do not attempt treatment yourself; isolate the hive and report it.

How to inspect brood

• Every time you open a hive, look at at least a few brood frames; in spring and late summer, examine every brood frame one by one.
• Hold the frame up to the daylight. If necessary, shake the bees off onto the top of the hive to expose the comb surface.
• Healthy brood: a compact, regular brood area; pearly white larvae curled in a "C" shape; dry, slightly domed cappings of uniform colour.
• Warning signs: a scattered, pepper-pot brood area; sunken, perforated, darkened or greasy-looking cappings; larvae that look yellowed, browned or melted; larvae or mummies thrown out in front of the hive.

Main diseases in the group

• American foulbrood (Paenibacillus larvae): A spore-forming bacterium; the larva dies after the cell is capped and turns into a brown, sticky mass. It is the most destructive brood disease; its spores survive for decades. Notifiable.
• European foulbrood (Melissococcus plutonius): The larva usually dies before the cell is capped; it turns yellow, twists and looks melted. Notifiable.
• Chalkbrood (Ascosphaera apis): A fungus; the larva turns into a white or grey-black, hard, chalk-like mummy. It increases in cool, damp springs.
• Stonebrood (Aspergillus species): A rare fungus; the mummies are stone-hard and covered with yellow-green powder. The mould spores can also cause respiratory problems in humans; wear a mask.
• Sacbrood (sacbrood virus): The larva dies under the capping at the prepupal stage; it turns into a fluid-filled sac, its head lifts up and darkens.

Non-infectious conditions that are confused with these: chilled brood (death of brood at the edges that the bees could not cover during a sudden cold spell), varroa damage (brood death caused by mites) and bald brood caused by wax moth larvae.

Differentiation table

Field findings point the way but do not give a definitive diagnosis. For foulbroods, field test kits (rapid tests) and laboratory analysis are used.

What to do if you suspect foulbrood

1. Close the hive and reduce the entrance; prevent robbing.
2. Do not move frames, honey, comb or tools from this hive to another hive.
3. Take photographs; note the date and the hive number.
4. Report it to the official veterinary service / local agriculture authority; sampling and laboratory diagnosis are carried out through the official authority.
5. Clean your gloves and hive tool; do not open other hives with the same equipment that day.

Seasonal calendar

Prevention

• Renew comb regularly; take old, dark combs out of circulation.
• Do not move frames between colonies at random; clean the hive tool and gloves between hives.
• Do not buy colonies, comb, second-hand hives or honey from unknown sources; do not feed your bees honey from another apiary.
• Work with lines with strong hygienic behaviour; a strong, well-fed colony with varroa under control protects its brood better.
• Prevent robbing: do not leave weak and dead colonies open.