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.
TransmissionChalkboard 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.