Chalkbrood and Honey Bee

Chalkbrood and Honey Bees


Chalkbrood is a fungal disease that affects honey bees, attacking honey bee larvae. The condition is not dire, and healthy honey bee colonies can usually stave off a chalkbrood infection. Prevention is therefore the best method of control; maintaining a healthy hive and taking precautions not to spread fungal spores are important in controlling chalkbrood.

The disease is caused by the fungus Ascosphaera apis, which is primarily associated with both social and solitary species of bees. Bee larvae ingest the A. apis spores during feeding; the spores then germinate in the intestines of the larvae, developing into fungi. The fungi will initially compete with the larvae for food, gradually starving the larvae. As the fungi then go on to consume the larvae themselves, they eventually engulf the larvae in a cottony, white mycelia (a mass of branching filaments) that harden in the cell. These larvae eventually become shrunken, chalklike mummies that are whitish or grayish in appearance; coloration is irregular. If a hive is otherwise relatively healthy, worker bees themselves will dispose of mummified larvae, effectively containing the infection. However, if a hive is weakened by other factors, such as mites or other predators, it is more difficult for the workers to cope with an outbreak of chalkbrood, and the infection can destroy the colony.

Although chalkbrood can occur at any time, lower temperatures increase the chance of outbreaks. The springtime is a common season for chalkbrood, when the brood nest is expanding rapidly and the smaller size of the adult workforce makes it difficult to maintain a constant temperature in the hive. Low-lying, cool apiaries are more prone to catching the disease. High humidity, too, can aggravate outbreaks of chalkbrood. If you maintain good ventilation in your hives and periodically tip the hives forward so that rainwater can drain out, humidity levels in the hive can be better kept under control.

Chalkbrood and Honey Bees


Chalkbrood occurs worldwide and is spread by pollen, drifting bees, and contaminated equipment. Beekeepers themselves are often cited as the primary carriers of disease, through insufficient hive hygiene. There are no chemicals or other substances known to currently counteract the chalkbrood fungus, so the best measures against the disease are preventative. Old brood combs can act as depositories for chalkbrood spores, so replacing combs on a regular basis can help keep a hive clean. Providing new foundations for combs regularly also helps prevent incidences of Nosema virus and other pathogen-driven diseases. Also, keep all your equipment sterilized and clean, and remove any chalkwood mummies from the hive immediately. The mummies themselves are highly infectious, and spores from the mummies can reinfect colonies via stored food supplies or direct transport to larvae by bees working within the nest. You should completely destroy any frames that are heavily infected. Don’t transfer frames that may be infected to other hives.

Some stocks of bees may be more resistant to chalkbrood than others. If your colony is susceptible, replacing the queen and thus adding new gene pools to the colony may help make the colony more resistant. If you have a regular supplier of bees and queens, discuss the issue with your dealer and get the best advice you can.

Although chalkbrood has been considered a relatively minor honey bee disease, it appears to be on the rise in the United States, particularly in subtropical climates such as Florida. Some specific areas have reported considerable infestations, reporting 30 percent or more of hives infected. Studies have suggested that the importation of pollen from abroad correlates with increased incidences of chalkbrood. Chalkbrood rarely kills off a colony, but the disease can considerably weaken a colony, thus reducing the honey surplus available for harvest by commercial beekeepers. However, proper hive maintenance and cleanliness should stave off most occurrences of the disease.