Which disease (A6)?

View answer

Correct answer: 5 (Chalkbrood)

Chalkbrood: The fungus Ascosphaera apis infects the brood of workers and drones. Fungal spores are ingested by larvae with their food. They germinate in the gut and form hyphae that grow through the larvae. When female and male hyphae meet on the larval body surface, gray-black fruiting bodies form and produce new spores. Fungus-infected larvae, also called mummies, darken and are contagious.

Depending on colony vitality and climatic factors (temperature and humidity in the hive), infestation may increase, colonies weaken and may perish—or, conversely, recover spontaneously. The highly resistant spores of Ascosphaera apis can remain in bee colonies for years or even decades and are able to develop whenever conditions allow.

Field symptoms and diagnosis:

• On the hive floor or early in the morning in front of the entrance and on the landing board, chalkbrood mummies are found: dead, dried bee larvae covered with a white (more rarely gray-black) fungal growth.
• Patchy brood areas; torn cappings.
• Live prepupae with a fine, white, cotton-like fungal coating.
• Dead prepupae covered with a fluffy, white fungal growth.
• Dried chalkbrood mummies, chalk-like and easily detachable from the cell.

Prevention and control

• Favor colonies with good vitality; reduce stress factors.
• Choose a dry, warm location with good nectar flow; do not allow colonies to starve; adjust hive space to the number of bees.
• Avoid overly old queens; select for hygienic behavior and colony development.
• Avoid uncontrolled inbreeding.
• Remove or unite weak colonies in good time.
• Maintain apiary hygiene; renew combs regularly.
• Avoid spread from contaminated colonies or apiaries (frames, brood, bees).
• Suspect frames can be disinfected by evaporating 60% acetic acid or formic acid using an applicator in a frame cabinet (approx. 100 ml for a volume the size of a Swiss hive).

In case of low infestation:

• Replace the queen with a selected queen.
• Stimulate hygienic behavior by spraying diluted sugar water onto the frames.
• Remove heavily contaminated combs and melt them down. The spores do not survive the thermal treatment during wax processing.

In case of heavy infestation:

• Create artificial swarms and house them in previously flamed hives with foundation and new frames; melt down all contaminated combs.
• Eliminate severely weakened colonies.
• Move colonies to more favorable locations.

What can the beekeeper do?

It is recommended to strengthen bees’ natural defenses against disease by applying the principles of good beekeeping practice. Colonies are healthy when they develop well (adult bees and brood), display good hygienic behavior, and produce good yields. In practice, these are referred to as strong or vital colonies (see cover image). Colony vitality depends on many factors. Beekeepers mainly have the following levers of influence:

• Apiary locations with good nectar flows (continuous food supply) and a suitable local climate.
• Regular creation of young colonies and replacement of weak colonies.
• Selection of queens with sufficient vitality traits (colony development, hygienic behavior).
• Regular renewal of combs.
• Varroa mite control in accordance with regulations – hygiene in the apiary.
• Caution when taking over bees from other locations (diseases!).
• Avoid any importation of bees from regions outside Europe.

► PDF poster: Recognizing diseases

► Next question ►►