Part three in this series of posts about the varroa workshops given by National Bee Unit inspectors at a special training day last Sunday. After lunch, sitting outside in the sunshine of the gorgeous Roots & Shoots garden, we went back inside for a bee viruses workshop with NBU bee inspector Caroline Washington.
Varroa mites help transmit several viruses to bees. These include deformed wing virus, sacbrood and acute bee paralysis virus. In Caroline’s opinion bee virus infection rates have got worse in the past 3-4 years. She believes the reason for this is more beekeepers, and more beekeepers not treating for varroa. This is a particular problem in big, crowded cities like London, where disease spreads fast. To help honey bees we don’t really need more beekeepers, we need better trained beekeepers prepared to look after their bees. And more flowers of course.
Also known as “chinese slipper”, because the infected larvae swell up and become fluid filled sacs lacking in the segmentation of healthy larvae. They then eventually die and begin to dry out, turning a dark brown to black colour, giving rise to characteristic ‘Chinese slippers’ or ‘gondola-shaped’ scales. The NBU’s Beebase Sacbrood page has some photos. Not a serious disease, as many hives have little patches of it. If it becomes a larger problem, it’s best to requeen or shake the colony onto clean comb.
A frame of sacbrood which Caroline passed round. We used tweezers to pull the dead larvae out.
Deformed wing virus
The major virus in the UK. Bees with deformed, shrivelled wings cannot fly and only live a few days. There are two main ways of transmitting the virus: horizontal and vertical.
Horizontal transmission is when infected bees pass the virus on through feeding brood or feeding other adult workers, drones and queens.
Vertical transmission results after a queen becomes infected during mating and subsequently her eggs are infected.
Some bees with deformed wings which Caroline passed round. Their poor little wings look like withered, tattered flakes.
The deformed bees were on the comb below. Note the perforated cappings, a sign that the workers have detected that something is wrong and tried to begin uncapping the larvae.
Chronic bee paralysis virus (CBPV)
If you see dark, hairless bees, they could be infected. Other workers will nibble their hair off because they smell different.
Long periods of bad weather and overcrowding in a colony can contribute to chronic paralysis. There are two forms of paralysis:
- Crawling bees with bloated abdomens and dislocated wings
- Dark, hairless, shiny bees rejected at the entrance (not to be confused with robber bees)
Both forms can appear in the same hive. Robber bees can also have a lack of hair from being involved in fights, but bees infected with chronic paralysis virus will be unable to fly properly. See the NBU’s Beebase CBPV page for photos and more information.
Has anyone reading this seen symptoms of any of these viruses in your hives? Emma and I had some sacbrood in Rosemary’s hive during the bad spring weather this year.