Varroa Strikes Again: How Mites Weaken Bees’ Own Venom Shield

Most beekeepers know Varroa destructor drains bees of their strength and spreads deadly viruses. But a new 2025 study has uncovered another hidden weapon in Varroa’s arsenal: it weakens bees’ natural venom-based immune shield.

Honey bee venom isn’t just for stinging predators; it contains melittin, a powerful antimicrobial compound. Bees actually coat their own bodies with venom during grooming, creating a kind of “external immune system” that helps defend against mites, fungi, and viruses.

The stinger apparatus of honey bees

This study found:

• Healthy nurse and forager bees naturally carry venom (melittin) on their bodies, drones and newly emerged bees don’t.

• Varroa-infested bees groom more, spreading more venom onto their bodies in an attempt to fight back.

• But here’s the catch: Varroa damages bees’ ability to produce melittin, especially if the mite attacks during the pupal stage. These bees emerge weaker, with less venom to defend themselves.

• Bee venom does slow down mite activity, but its effect is modest compared to propolis or other defences.

  
  

Take-Home Messages for Beekeepers

• Early Varroa control is critical: Infestations during brood stages cause lasting damage to adult bees’ natural defences.

• Support multiple lines of defence: Propolis, good nutrition, and reduced mite loads all help compensate for weakened venom immunity.

• Don’t rely on grooming alone: While bees try harder when infested, grooming by itself is not enough to control mites.

• Stronger colonies mean stronger immunity: Keeping Varroa levels low ensures bees maintain their venom shield against diseases.

  
  

This study reminds us that Varroa isn’t just stealing resources; it’s undermining bees’ very immune systems. Staying ahead of mites means healthier, more resilient colonies.

Find the publication here: Pusceddu et al 2025. “Varroa destructor weakens the external immunity of western honey bees by impairing melittin production” https://www.nature.com/articles/s41598-025-13440-2