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Chalkbrood Disease


Ohio Department of Agriculture
Division of Plant Industry – Apiculture
8995 East Main Street
Reynoldsburg, Ohio 43068-3399

Cause:  Ascosphaera apis is the fungus that causes chalkbrood disease.  It was first confirmed during 1974 in Ohio in the counties of Ottawa and Erie.

Effect:  Honey bee brood is affected, causing the larvae to become mummified.  Infected larvae ingest spores of A. apis within their food when they are about three to four days old.

Symptoms:  Chalkbrood disease is relatively easy to diagnose from the other bee diseases if you know what the disease looks like.  The infected larvae are uncapped by the bees and can be easily removed from the cells.  At first the larvae (mummies) are spongelike but as they dry they become hard and “chalk like” in appearance.  The dried mummies will either remain whitish or turn a grey/black color.  They are often seen in the cells of the brood comb.  However, if the bees remove the larvae they can also be on the bottom board or in front of the hive.

Spread:  The spores of A. apis are quite resistant and can remain viable for at least 15 years.  Disease spores can pass from bee to bee during food exchange and queen bees can transmit the disease (DeJong & Morse, 1976).

Drifting of bees from infected colonies spreads the disease, also when contaminated tools and combs are interchanged between infected and healthy colonies (Barthel, 1971).

Inbred lines of honey bees seem to be particularly susceptible to infection (Moeller & Williams, 1976).

Control:  Chalkbrood is not considered to be a serious disease, however,  in sever cases bee populations are reduced resulting in lost honey crops.  Currently there is no chemical registered for use against this disease.  Beekeepers, however, can do the following:

  1. Combs containing large numbers of mummies can be destroyed.
  2. Add bees and brood to badly weakened colonies (make sure disease free).
  3. Requeening with a stock that is less susceptible or possesses better cleaning behavior.
  4. Using good management practices to keep the colonies strong.


Prepared by: Gordon Rudloff
State Apiarist
Ohio Department of Agriculture