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Updated: Apr 30

Chalkbrood is a fungal disease that can appear very alarming, but is usually overcome easily by your bees with a bit of intervention. We tend to see chalkbrood in the spring, particularly when the weather is cool and damp for an extended period. It is usually caused by lack of warmth and poor nutrition.


  • Black and white mummified "nuggets" in cells, on bottom board, or on the landing board (it is good to see them on the landing board as it means the bees are trying to clear the fungus out of the hive).

  • Patchy brood

*not my photos

Not-so-fun fact: The black bits are the fruiting bodies and the white is the mycelium.


  • Feed colonies 1:1 in spring

  • Don't add boxes too soon

  • Don't split too aggressively

  • sanitize hive tools between hives/yards

  • cycle out old frames


  • Reduce hive space

  • Feed 1:1

  • Clean as many "mummies" out of the hive as possible. Scrape/sweep bottom board, bang frames to dislodge them from cells.

What does the Research Say?

This article describes an experiment where they exposed chalkbrood infected larvae to different levels of chill and humidity to see how it affected mummification. Mummification (yes, that's actually the word scientists use for it!) happened far more frequently following a chill and at higher humidities.

This study tested how age of comb affected chalkbrood infection and found that infection rates were much greater in old comb (and they used some REALLY old comb).

Looking for more?

Looking for more beekeeping education? You can find my virtual, on-demand course Intermediate Beekeeping for Year 2 and Beyond at

Or if you'd prefer a more tailored experience, you can join my mentorship group at


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