Sacbrood

Sacbrood is caused by the sacbrood virus.

Age of brood affected

Sealed brood 7-10 days old and pupae.

Both worker larvae and sometimes drones are affected by sacbrood.

Infection method

Nurse bees transmit the virus when they feed larvae with brood food from their hypopharyngeal glands.

The virus can survive up to 4 weeks in:

• larval remains
• honey
• pollen.

Symptoms

The following signs may indicate sacbrood infection:

• discoloured larvae, changing from glistening pearly white to:
  • yellow
  • grey
  • light brown
  • dark brown
  • mostly black
• cell position of larva is fully extended at the bottom of the cell with its head raised towards the top of the cell – it can be easily removed without damaging the cell wall
• dead larva skin changes to a plastic-like sack
• body segmentation is maintained
• a putrid odour may be detected in advanced stage of infection.

Treatment

Sacbrood is rare because adult bees can detect and quickly remove infected larvae.

Follow these steps to help a hive recover:

1. Re-queen with a young vigorous queen.
2. Introduce young, disease-free bees.
3. Move bees to better conditions with a good honey flow.
4. Feed bees sugar solution and quality pollen if supplies are low.
5. Pack bees down into fewer boxes.
6. Replace combs.

Diagnosing sacbrood

Send a comb sample with brood in a waterproof container to: