Learn How To Keep Your Hive Safe

Stonebrood is a fungal condition that affects both larvae and adult bees. The name comes from its effect on larvae – when they’re infected, they harden, turn black and resemble small stones.

As a beekeeper, you need to be aware of potential diseases that could infect your hive. While stonebrood is a rare disease in Australia and hasn't been identified here in New Zealand, it’s always good to be informed and aware of the existence of such diseases.

Here’s everything you need to know about stonebrood – what to look for and how to protect your bees.

Understanding stonebrood

Stonebrood is a rare and usually short-lived disease caused by the fungi Aspergillus flavus and Aspergillus fumigatus, found in soil. These fungi infect both larvae and adult honey bees. They show up in the gut of adult bees after larvae ingest conidiophores (spores).

Stonebrood can be fatal in severe cases, with toxins from the fungi killing and mummifying the larvae before they hatch. There have been cases of stonebrood reported in Australia, North America, Europe and Venezuela.

The spread of stonebrood

The fungi’s spores are released from the soil and circulate through the air, where they land on food or attach to combs and beekeeping equipment. Spores can be transmitted between colonies when bees land at the wrong hive, through feeding with contaminated honey or by using combs that are infected. The best prevention is maintaining best beekeeping practices and clean, vibrant hives.

How to detect stonebrood

At the beginning of a stonebrood infection, larvae will lose their glistening appearance and become dull and fluffy, and then turn yellow or green-brown. They can shrink and become mummified within a day.

If adult bees die of stonebrood, they usually do so outside of the hive and it can be difficult to detect an infection.

But, there are some behavioural signs to look for:

  • Agitation, paralysis or weakness
  • Inability to fly away from the hive
  • Swollen abdomens or morphological changes
  • Crawling bees outside the hive
  • In severe cases, mummification

Stonebrood vs chalkbrood

An infection of stonebrood can have similar symptoms to chalkbrood. Both are fungal diseases of honeybees, but chalkbrood is caused by Ascosphaera apis and affects the brood, whereas stonebrood is caused by different fungi and affects both the brood and adult bees.

Chalkbrood is ingested by the larvae, then goes through the gut wall and absorbs all the nutrients, starving it. Larvae infected with chalkbrood release millions of spores, and the fungus can remain infectious for a long time, whereas stonebrood doesn’t survive long. Chalkbrood presents in larvae as a sponge-like appearance, while stonebrood has a hardening, mummifying effect.

Protection and prevention

Stonebrood disease is spontaneous – often, it comes down to whether there are spores in the soil around your hives. As with many diseases that affect bees, the best chance of prevention is maintaining a healthy hive, so your bees are prepared to fight off infection on their own.

Here’s what to do:

  • Check your hives regularly, and report any unusual activity to your local government pest control body
  • Locate your hives responsibly – ensure the bees have good sun exposure and avoid wetlands
  • Manage your hives – waterproof and repair them to keep water out
  • Clean and sterilise beekeeping equipment and tools frequently, including clothing
  • Remove any dead larvae from the hive and burn any infected combs well away from the hives

If hives have been neglected, are heavily infected and the disease cannot be controlled, the advice is to destroy them, and not use any honey from them for human consumption.

Keeping up as a beekeeper

Although rarely encountered, it’s still important to be aware of stonebrood signs and prevent them from intruding on your hive. Your best chance of fighting off an infection is to maintain best beekeeping practices and check your bees regularly. If you do notice any symptoms, act quickly and report them to your local beekeeping organisation.

Want to learn more about honeybee diseases and pests? Check out our article here.