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Chalk brood, Ascophaera apis, brood mycosis, Pericystis apis, call it what you will...

posted Nov 15, 2018, 9:19 AM by Helen Mooney   [ updated Nov 15, 2018, 10:52 AM ]
Winter is a good time to catch up on some reading, and whilst I prefer to trawl the internet for the most up-to-date literature, particularly on diseases, sometimes I find books of historical interest that can be useful in providing background information that can still help us to understand the disease and how it affects out bees today.

For example, today I was reading about Chalkbrood, that fungus that has proved particularly problematic this year, according to fellow beekeepers and from my own experience.  For a long time now, we believed that re-queening the colony straight away with a queen from a different genetic line, along with a Bailey frame change if the infection was severe, would get us back on track.  But some beekeepeers reported this year, that changing the queens did not help.  There could be many reasons for this as there can be many reasons for an explosion in the growth of this fungus in certain colonies.  Stress is certainly a factor in addition to genetic predisposition.  Again, this is why it is important to keep hive records- we do not want to breed from susceptible colonies and we need to know early next season which colonies to prepare for a complete frame change, if it was not done last season.

Tracing the history of a disease is very interesting and 1930 is the earliest reference I can find to a study on this pathogen, which was discovered just before the 1900's, though some modern books on disease say it was not detected in the US until as late as the 1960s.  We have come along way since then in terms of being able to see the spores under the microscope, extract and analyse the DNA and now we know that a healthy population of friendly gut bacteria plays a huge role in the health of the honey bee (we might come back to that) in that they can complement the bee's immune system and also contribute to the nutrition of the bee by breaking down cellulose in pollen grains, thereby making the protein available to the bee.  A healthy gut microbiome needs an acidic pH, something that artificial feeds interferes with. This brings us back to the belief that prevention is better than cure, and poor nutrition in itself can be one of the stressors that triggers this opportunistic pathogen. 

There isn't scope here to cover all aspects chalkbrood (I don't think it is worth mentioning some of the proprietary concoctions that you may care to spend your money on, there are no licensed treatments in any case) , but hopefully beginners will now be prompted to think about how to proceed if you have had a problem with the disease last year- don't just think it has died off once brood rearing has ceased.  The spores can survive hostile environments for years, so acetic acid fumigation will be necessary for all equipment bar old brood wax, which should be burned.  If the infection was low to medium last year, more than likely it will be building up slowly between now and next summer, so doing nothing is not an option.  In the meantime, another more modern book on diseases I find useful is "Honeybee Veterinary Medicine: Apis mellifera" by Nicholas Vidal Naquet,  and "Having Healthy Honey Bees" by Irish Scientist, John McMullan. 

For anyone with a more general or academic interest in how insects cope with infections and parasites, the book "Insect Infection and Immunity" edited by Jens Rolff and Stuart E. Reynolds, is now available to download from Google books for free.
Below: Left: chalkbrood spores from one of our infected larvae (compound microscope x400), below, right: fruiting bodies of a mummified larva earlier this year as seen through a stereo microscope x20.