Chalkbrood Disease

Chalkbrood disease is a disease of honeybee larvae which is caused by the fungus Ascosphaera apis. It infects honeybee larvae (brood) through ingestion of spores of the fungus. The spores then germinate in the gut, ultimately leading to death by starvation. It only infects larvae that are three to four days old.

Increased incidences of chalkbrood disease occur in the spring when the colony is rapidly growing and a smaller honeybee adult workers are not able to maintain the temperature of the brood nest. Chalkbrood has resulted in serious damages to bee populations throughout North America, Europe, and Australia over the years.

High incidences of Chalkbrood mostly indicates poor hygienic behavior and stress due to weather, poor management or diseases. Hives that are drafty, damp, lying in low spots, or heavily overgrown with vegetation are more susceptible to chalkbrood disease. Because old combs harbor spores of the disease, brood combs should be replaced at least every five years to improve brood production.

Hives infected with chalkbrood have a scattered brood pattern with perforated cappings. Infected larvae usually die after capping and the fungus grows to fill the cell, causing the larvae body to dehydrate and form a 'mummified' appearance which appears shrunken, hard and chalklike. The fungal mycelium infiltrates the larval tissue that gives it its white-grey color.

Transmission

Chalkboard disease is spread between hives through drifting behavior of worker bees and drones and robbing behavior exerted by worker bees. Contaminated equipment, hive, and beekeeping equipment can also infect colonies, since the Chalkbrood spores can remain in an environment for up to 15 years. Combs, pollen and water can also be contaminated.

Symptoms

  • Scattered brood pattern with perforated cappings
  • Larvae dies after capping
  • Larvae appear as mummies and chalklike
  • Dead larvae found in cells, hive entrance and bottom boards
  • No ropy thread present

Cause

  • fungus - Ascosphaera apis

Diagnosis

  • Clinical signs

Treatment


Management Treatments
  • Adopt the size of the hive to the strength of the bee colony.
  • Stimulate hygiene behavior
  • Ensure that the colony has a strong worker population, and that the hive is well ventilated and free from accumulated moisture.
  • Replace the queen with one supplied by a reputable bee breeder.
  • Remove and replace diseased combs which can act as a reservoir for the spores. Clean up mummified larvae found in bottom boards and around the entrance of the hive.
  • If early stages of Chalkbrood infection, add young adult workers and hatching brood, combined with sugar-syrup feeding.

Prevention

  • Select bee stocks for hygienic behavior
  • Perchase hygienic queens
  • Maintain a warm, dry hive interior
  • Hives should lean forward slightly so that rainwater runs out the entrance instead of accumulating inside.
  • Screen hive floors for varroa control.

Article Reference

  • image