Ascosphaerosis

Ascosphaerosis, commonly known as chalkbrood disease, is a serious fungal infection affecting honey bee brood, caused by the fungus Ascosphaera apis. This disease is a significant concern for beekeepers worldwide as it targets bee larvae, leading to their death and eventual mummification, which visually resembles small, chalk-like pellets.

The causative agent, Ascosphaera apis, is a fungus that infects larvae after they ingest spores through their food. Once inside the larval gut, the fungus germinates and begins to consume the larval tissues. Eventually, the fungus erupts through the cuticle, covering the larva in white mycelium, which later hardens and turns dark as the spores mature.

Clinical signs of the disease are typically observed by examining the hive floor or the entrance, where dead, chalky larvae are found. Inside the comb, cells may appear to have mummified larvae that are either white or black, depending on the stage of fungal development. Heavily infected colonies show signs of distress, reduced brood production, and a decline in overall population strength.

The development of the fungus is highly dependent on environmental conditions. High humidity, poor hive ventilation, and cool temperatures are primary factors that favor the spread of the infection. Chilling of the brood, often occurring during unpredictable spring weather, makes larvae significantly more susceptible to the fungal invasion, allowing it to take hold within the colony.

Management of ascosphaerosis involves improving hive hygiene, ensuring proper ventilation, and replacing heavily infected combs. In severe cases, antifungal treatments approved for veterinary use in apiculture are required. Long-term prevention focuses on maintaining strong colonies with good nutrition, utilizing bee strains with hygienic behavior, and replacing older queens to ensure vigorous colony development.