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One Bee Trait, Double Protection: How VSH Bees Fight Both Varroa and Chalkbrood

  • Writer: Frank Jeanplong
    Frank Jeanplong
  • Aug 31, 2025
  • 2 min read

Beekeepers know the struggle: Varroa mites weaken colonies, while chalkbrood fungus quietly reduces brood survival. Managing both can feel like an endless battle. But what if one bee breeding trait could help control both problems at once?


A new study published in PLOS One (Dyrbye-Wright et al., 2025) has found that honey bees bred for Varroa Sensitive Hygiene (VSH), a trait that allows bees to detect and remove mite-infested brood, also show resistance to chalkbrood disease.


Early signs of chalkbrood. (A) Acuminate heads (red arrow) and amorphous pre-pupae (blue arrow) are both are early signs of non-infectious chalkbrood. Grey arrows show a cell where worker bees have started to remove the wax capping of cells (B), revealing a pre-pupae underneath that had early signs of chalkbrood (C).
Early signs of chalkbrood. (A) Acuminate heads (red arrow) and amorphous pre-pupae (blue arrow) are both are early signs of non-infectious chalkbrood. Grey arrows show a cell where worker bees have started to remove the wax capping of cells (B), revealing a pre-pupae underneath that had early signs of chalkbrood (C).

What the researchers did

Over two years, researchers compared VSH-bred “Pol-line” colonies with commercial hygienic colonies across trial sites in Minnesota and Louisiana. Colonies were challenged with Ascosphaera apis (the chalkbrood fungus) and monitored for signs of infection, hygienic behavior, and mite levels.


Key findings for beekeepers


  • VSH bees held strong against chalkbrood – They were just as resistant as commercial hygienic colonies, and in some trials had significantly fewer infections.

  • Stronger mite resistance – As expected, the VSH colonies carried fewer Varroa mites in most trials.

  • Dual defense trait – The same behavioral response that helps bees remove mite-infested brood also works against diseased brood.


Why this matters for your apiary


  • Fewer treatments, healthier bees – By using VSH queens, you could reduce chemical interventions while maintaining brood health.

  • Improved survival & savings – Colonies that withstand both parasites and diseases are more resilient, helping cut losses and protect your investment.

  • A breeding direction worth supporting – Selecting for VSH could give beekeepers a powerful tool to fight two of the most costly challenges in modern beekeeping.


Take-home message

If you’re looking for bees that can stand up to mites and brood diseases, consider VSH stock. This study suggests they aren’t just mite-resistant, they may offer double protection that keeps colonies stronger, longer.


Find the study here:

 
 
 

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