The meeting was introduced by Andrew Halstead, Weybridge Chairperson, who reminded us that Varroa arrived in the UK in 1992.
There were two talks, one by Jonathan Brookhouse of Guildford division and the other by Marion Cooper of Weybridge.
“Searching for resilience in our honeybees” by Jonathan Brookhouse
Jonathan started by stating that he was aiming for resilience and not resistance to Varroa. Bees already have to cope with diseases, pests, climate change, environment change and modern beekeeping practices. Jonathan stated, ‘our bees need to be allowed to evolve together with the parasite.’
Why not treat bees for Varroa? There were various reasons posed, such as: residues in wax and honey, miticide damage to bees including queen longevity, drone development and disturbance to gut biome. His main concern is that the bees will become reliant on beekeeper intervention and that treatments will become ineffective when the mites become resistant to the treatments as has already occurred in many parts of the world.
Jonathan then looked at how bees are coping with Varroa. One study of 150 colonies on an isolated island that were untreated for Varroa between 1999-2005 resulted in only 13 surviving colonies. He looked at various studies on hygienic behaviour, which is measured by the efficiency with which bees remove dead brood from comb. More recent studies have placed Varroa mites under living capped brood to see if the bees will uncap and remove the larvae (and therefore the mites as well, interrupting the reproductive mite cycle). Ron Hoskins of Swindon Conservation Group has not used miticides since 1995. His bees apparently attack and remove Varroa mites.
They have also been shown to have Deformed Wing Virus (DWV) type B, which is not virulent and confers protection against virulent types A and C. Could this DWV variant be the answer to the problem of vector viruses?
Jonathan is also against importing bees as the European descendancy of bees from Africa takes a different route from that of the Eastern European and Middle Eastern bees. Debbie’s notes: (1) although speciation has not occurred so crossing should result in hybrid vigour. (2) All of this was very interesting, but I can see no way forward other than to stop treating your bees and cross your fingers!
‘Are there Varroa tolerant bees?’ by Marion Cooper
Marion gave an excellent recap of how Varroa was found across the UK in 1992, pointing out that Varroa became resistant to pyrethroid insecticides by 2006. Many Weybridge members suffered colony losses, although it was noted that there was not always a correlation between mite numbers and the state of the colony. There were various theories at the time about how some bees were surviving without treatment. Mostly this was championed by Ron Hoskins and his ‘bee to save all bees.’ However, if one of his queens was introduced to a distant colony there appeared to be no protective effect. It may be that isolation on Salisbury Plain was his saviour (as well as DWV type B).
In the late 1980s and 1990s Varroa was found to be a vector of viruses, the most pathogenic being DWV. Research on this is ongoing, much of it being continued by Prof Stephen Martin at Salford University and some others, and Marion suggested that we look out for the papers that he will no doubt continue to publish. Marion pointed out that without controlling Varroa we cannot control viruses. Colonies will survive for two to three years but will eventually collapse.
Most people attending treated their bees for Varroa. Marion advised to do mite counts, treat colonies if necessary and rotate treatments used to limit resistance developing.
Jonathan suggested that if the whole of Weybridge stopped treating their bees, then eventually we might get Varroa tolerant bees! Most people would find their losses high, however.
There appears to be no true ‘Varroa resilient bee’ as yet. However, organisms evolve and this is eventually possible but on a much longer time frame for the bees due to their slow generational turnover. How long? Who knows?
In the meantime I shall continue to treat my bees as necessary and keep abreast of current research and methods.