I caught this interesting story about some local bee keepers on the news last week.
[quote author=Western Morning News]
Westcountry scientists' research offers hope to save bees
New hope in the battle to protect the honey bee has been offered by scientists in the Westcountry.
Colony collapse blamed on the Varroa destructor mite is a major worry in farming as up to a third of the food we eat depends on pollination by bees and other insects.
The deformed wing virus (DWV) carried by the mite is believed to be one of the reasons why bee numbers have halved in the UK in the last 25 years.
Now researchers at the Marine Biological Association (MBA) in Plymouth have
solved the riddle of why one bee colony has survived despite high levels of infection by the virus, which wiped out its neighbours.
They discovered that the survivors were infected by a different type of DWV, which the MBA scientists suggest is dominant and protected the bees against the lethal variety.
The lead researcher said the findings pointed to a natural solution to the colony collapse problem.
“It was great to see that through the process of natural selection, honey bees, Varroa and DWV were able to reach a stable state, with honey bee colonies able to survive without the use of a chemical Varroa treatment,” said Gideon Mordecai.
The MBA scientists used new methods of DNA sequencing to show that the surviving colony had two types of DWV carried by the Varroa mite, one lethal and the other not.
Only the non-lethal type was detected in the bees themselves.
The scientists suggest that infection by the non-lethal DWV prevented the more virulent variant from becoming established.
Mr Mordecai is a PhD student with the University of Reading, based at the MBA on Plymouth Hoe. He studied samples provided by the Swindon Honeybee Conservation Group.
DWV is closely related to a marine virus studied by the MBA’s Schroeder Research Group. DWV particles are not all identical, but made up of a swarm of three major variants. One of the types was recently discovered by the authors of the research, which appears in the ISME Journal (International Society of Microbial Ecology).
Varroa destructor has spread from Asia across the world in the past half century.
Other factors blamed for the decline of the bee include the destruction of flowery habitats where the insects feed and the widespread use of pesticides on crops.
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Here's the abstract from the related paper.
[quote author=The ISME Journal]
Superinfection exclusion and the long-term survival of honey bees in Varroa-infested colonies
The ISME Journal advance online publication 27 October 2015;
Gideon J Mordecai, Laura E Brettell, Stephen J Martin, David Dixon, Ian M Jones, and Declan C Schroeder
"Over the past 50 years, many millions of European honey bee (Apis mellifera) colonies have died as the ectoparasitic mite, Varroa destructor, has spread around the world. Subsequent studies have indicated that the mite’s association with a group of RNA viral pathogens (Deformed Wing Virus, DWV) correlates with colony death. Here, we propose a phenomenon known as superinfection exclusion that provides an explanation of how certain A. mellifera populations have survived, despite Varroa infestation and high DWV loads. Next-generation sequencing has shown that a non-lethal DWV variant ‘type B’ has become established in these colonies and that the lethal ‘type A’ DWV variant fails to persist in the bee population. We propose that this novel stable host-pathogen relationship prevents the accumulation of lethal variants, suggesting that this interaction could be exploited for the development of an effective treatment that minimises colony losses in the future."
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And this from the website of the beekeepers involved. Interesting to note that use of chemicals would only seem to have worsened the problem of verroa over time.
[quote author=Swindon Honeybee Conservation Group]
My Research – by Ron Hoskins, Swindon Honeybee Conservation Group
(Phase 1)
Back in the ’90s
In 1992, when Varroa mites were first discovered in Devon I attended a MAFF workshop to learn more about the mites from their scientists. Among other things they advised
the use of tobacco smoke and sticky floor inserts to catch falling mites, therefore controlling its numbers.
By keeping their numbers under control it was thought Varroa may not cause colony loss. However, tobacco soon went out of favour and other means of control were sought.
Subsequently beekeepers in Britain followed the lead of American and European beekeepers in what was already happening and began using a variety of chemicals, some of which are still being used today, like Formic and Oxalic Acids. Both of which can be quite dangerous to humans, and not very kind to honeybees. The mite has become immune to at least one favoured chemical, Pyrethroid.
Some chemicals are now to be found resident in recycled beeswax after it has been heated, cleaned and processed for re-use in beekeeping.
One can only wonder about the same recycled beeswax being used in cosmetics, creams and soaps, etc. for human use.
Also at that workshop the Varroa mite was described as “having a carapace like a crab” and “eight truncated legs like a crab“. At the time that description caused me to believe they were “hard and bony like a crab”. I was wrong. I later found out that adult Varroa are covered in hairs, soft, fleshy and very easily damaged.
This I discovered almost by mistake in 1994 when I decided to collect some Varroa mites to photograph at home with my Pentax 35mm slide camera attached to my microscope.
I inserted newspaper into the hive and allowed a few days for mites to fall onto it then removed and folded it. I stuffed it in my pocket and took it home. Upon inspection, not only were the mites covered with hive debris but they were also damaged. Certainly not worth wasting film on.
Though extra care was taken during later collecting I still found high numbers of damaged mites from one or two particular hives.
It became obvious that the bees in these colonies appeared able to ‘deal’ with the mite and I needed to know how that was possible.
Following a couple of experiments I was able to prove the damage was being inflicted by worker bees biting the mites from each other. I was also able to determine this was a genetic function and not a learned activity.
I used one exceptional colony for the start of a breeding program which has developed over the last nineteen years.
Regular mite collecting and checking, using a 20/40 dissecting microscope, still takes place to enable improved selective breeding. Nowadays a very fine artist brush is used to gently collect and examine the mite in order not to inflict more damage. Collecting from a varroa tray which has been in place for about three days is easy as there will be only a small amount of other debris. The damaged carapace or missing legs are very obvious
The last two years have been made easier for me as two colleagues now share the evaluation task.
In the 198’s I had been successful at instrumentally inseminating queen honeybees, nearly always accepted by their new colony. By 1995 my inseminated queens were no longer being accepted. The workers killed my queen and made one of their own.
The only thing that had changed in my bee husbandry at the time was the arrival of Varroa and my use of chemicals.
Around the same time I had joined forces with a beekeeping friend. We had about eighty colonies between us.
We could do little about Varroa but the chemicals were different. We made the decision to stop using them. This decision has since been upheld by scientific papers. From them came the knowledge that most chemicals being used at that time, and which are still being used, were the major cause of queen failure due to their adverse effect on the viability of drone semen. They also cause several other problems, one being the life-span of the bees.
If you “Google” The Effects of Miticides on the Reproductive Physiology of Honey Bee… you will find that Lisa Marie Burley, USA, has published her degree papers where she has drawn together many scientific papers which make interesting reading regarding
the dangers and damage of Varroa control chemicals in everyday use by beekeepers worldwide. There are lots of pages so I suggest you start reading from page 6, 2.2 Miticide Use and The Effects on Honey Bees.
All our hives were relocated to a new site in 2004. They are now ALL fitted with Varroa floors; a wire mesh floor and deep removable under-tray to catch falling mites for later collection and assessment. Hives and trays are numbered for record purposes. Mites are carefully collected from the trays on a near-weekly basis making it easier to keep mites fairly free of hive debris and undamaged by us, placed into numbered mini-pots then examined under a dissecting microscope later.
(Phase 2)
A new discovery was made
In the next two years about 50,000 mites were examined for signs of hygienic behaviour by the bees. Many thousands of them were found damaged, typically with carapace damage or legs removed. By 2014 around half a million mites had been checked.
In 2007 a new discovery was made. A colony was discovered where the worker bees seemed able to detect that Varroa were breeding upon the larval bees within capped cells. The cells were being opened and the bee pupae being removed and discarded from the hive.
My aged eyes are beginning to get the better of me so I now needed a strong lens to find the mites. I purchased a 7x loupe with LED’s.
During routine mite collecting I noticed that the Varroa tray of one hive had a central area completely clear of any hive debris. The mesh floor had a similar area above it where debris had collected and not fallen through. The floor was replaced for examination and cleaning. Using the new lens one of the first things I noticed were the almost transparent bee antennae (left). These had obviously come from immature bee larvae. I had not observed them before; the new lens made it possible now.
As these incomplete antennae are not to be found in other hives it suggested that the bees of this hive must be uncapping brood cells which contained Varroa mites and removing the larva and the mites.
The head of the pupae bee and its antennae are immediately behind the capping and would be the first parts to be tugged at by the workers. The woven wire screen floors allow some of these parts fall through onto the tray beneath The picture to the right shows a cell having been uncapped by worker bees.
Other colonies were found to be uncapping but not quite to the same degree.
When looking much closer among the floor debris i also found very tiny baby mites about I/6th the size of an adult. These fall from the bee larvae as they are being pulled from their cell.
The picture left shows lots of very young baby mites with an adult mite for comparison. A very high number of baby mites collected from that initial hive in 2007/8 proved that this hive was really getting the better of Varroa.
That colony was selected to play a major part in our future breeding programs.
Hygienic bee success
By now we had around 50 hives that have seen no form of Varroa control for many years, other than the grooming by the bees; no chemicals, shook swarm or drone culling. First the grooming and now the pupal bee removal causes a major set-back in the mite breeding cycle and dramatically reduces the potential build-up of mite population.
The adult female varroa mite is capable of reproducing several generations; her daughters have the same potential. Therefore by the simple removal of baby mites and the grooming of adult mites, the bees have prevented a mite build-up of thousands. They are now independent and need no further help from me. My job now is to breed hygienic queens and distribute many more of them.
To date lots of drones and queens were bred and distributed around Swindon. Some were retained for our studies. Queens heading colonies not showing a high degree of hygienic behaviour are culled and replaced with queens bred from some of our better stocks .
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