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EFB is a bacterial disease of honey bee brood. It is generally considered less virulent than American foulbrood and colonies sometimes recover from infection. Its field symptoms are easily confused with those of AFB, but there are important differences. Instead of being a healthy pearly white, larvae with EFB appear off-white, progressing to brown, and are twisted in various positions in the cell. Larvae with EFB usually die before they are capped whereas larvae with AFB die after they are capped.

The sanitation precautions recommended in the section on AFB apply also to EFB. Likewise, bee stocks selected for hygienic behavior can be expected to minimize outbreaks of EFB. The disease sometimes goes away on its own at the onset of a strong nectar flow. The beekeeper may be able to control the disease by simulating a nectar flow (by feeding sugar syrup) and by requeening the colony.

Preventive biennial treatments with Terramycin (or Tylosin) antibiotic, as recommended in the section on AFB, will also prevent EFB. As with AFB, it is important to consider antibiotic treatments as a preventive measure, not a cure. Terramycin treatments in EFB-infected colonies may actually be counterproductive because the medication permits those infected larvae to survive which would otherwise perish. These survivors then persist in the colony as a source of contamination. If the infected larvae are instead permitted to die, the house bees eject them from the hive and with them goes the source of infection. The bacterium does not form long-lived spores that persist on hive surfaces.


Chalkbrood is a disease of bee brood caused by a fungus, Ascosphaera apis, which was discovered in the United States in 1968. The larvae must ingest the spores of the fungus in order for the infection to occur. It only infects larvae that are three to four days old. There are no chemical treatments for this disease. Instead, it can be controlled by bee breeding and good management. The infected larvae are quickly covered by the white cotton-like mycelium of the fungus which eventually fills the entire cell. The white/grey mass soon hardens, forming a hard, shrunken mummy which is easily removed from the cell. The larva in the cell will resemble a chunk of chalk, hence, the name of the disease chalkbrood.

Bee stocks selected for hygienic behavior can be expected to minimize outbreaks of this disease. Hygienic queens are available from nationally-advertised queen breeders. See advertisements listed in American Bee Journal [www.dadant.com], Bee Culture [www.airoot.com], and Speedy Bee [www.abfnet.org]. Another way to minimize the disease is to maintain a warm, dry hive interior. Hives that are drafty, damp, lying in low spots, or heavily overgrown with vegetation are susceptible to chalkbrood disease. Hives should lean forward slightly so that rain water runs out the entrance instead of accumulating inside. If a hive is moist, prop the lid to air out the interior. Old equipment should be replaced or repaired if it has large gaping holes that permit entry of moisture and drafts.

Some operations have recurring problems with the disease that are not easily traced to season or management practices. This may suggest a genetic susceptibility in the bee

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