Oxford Bees

Deformed Wing Virus

Crawling bees and signs of Deformed Wing Virus prevalent across hives

Submitted by will on Sun, 26/05/2019 - 07:00
Dead bees outside the hive. They have likely died after being severely infected with Deformed Wing Virus

Colony 1 has been continuously occupied for over 6 years. Every spring, except 2018, there have been bees crawling around outside the hive -- stricken with Deformed Wing Virus or some other paralysing virus. These bees became food for Sparrows.

This year seems worse than previous years. There appear to be more bees crawling and for longer. This might not be worse than usual but it feels it. In April it was mostly Drones which were crawling around. Now it is more likely to be workers.

Last season had a very cold spring. Four out of seven colonies died from starvation or isolation starvation (ie there were too few bees to reach the few stores that were left). There was a definite brood break which will have reduced the number of Varroa and may have been the reason that there were very few crawling bees that season. Observing crawling bees is confused by the Sparrows eating them. I think that in 2018 there was very little Sparrow activity.

This season there have been warmer temperature. I can't say for sure whether there was a brood break. There have been higher than expected levels of Varroa this season which suggests that any brood break that did happen had a limited effect on Varroa numbers.

All this points to higher stress in the established hives this season. Conventional wisdom would suggest that there will be colony failures. Perhaps this will happen. I would expect that this would be seen as colonies succumbing to robbing by wasps or other colonies if it does. We'll see what happens.

No crawling bees outside Hive A

Submitted by will on Mon, 07/05/2018 - 07:19

For at least the last 2 years there have been flightless bees crawling around outside Hive A. These bees were clearly suffering from Deformed Wing Virus or another disabling virus. This year there are none.

The cause was explained to me by a researcher at University of Salford. All winter the Varroa mites feed from worker bees. They accumulate DWV virus particles. In spring, when brood production increases they rush in to infest the new brood and transfer more virus to them. These bees show visible signs of DWV -- deformed wings or an inability to fly.

The absence of crawling bees can be explained in several possible ways.

  1. There are fewer Varroa mites in the hive. I usually check this by looking at the removable floor of the hive. I've found dozens of ants on the floor so I don't know whether they've been taking the Mite bodies away. I don't think that this is what's happening.
  2. The overall number of virus particles has fallen in the hive. It was very cold in April this year. This should have stopped the bees rearing brood. Virus is removed from the hive by bees or mites leaving the hive. If more mites died during April then it might explain some of the reduction.
  3. There are fewer brood this year. This seems most likely. The activity at the hive entrance is quite slow. I did look inside the hive and found only one frame of brood which was capped. I may have overlooked uncapped brood but it points to there being fewer bees and fewer brood. They're taking longer to build up this spring.

On reflection I think that Colony 01 is smaller this year which would mostly explain the absence of crawling bees.

Mite Crisis in Hive E

Submitted by will on Tue, 12/09/2017 - 23:01

Hive E is having a Varroa mite crisis. I checked today and for the previous 2 weeks. Each time I found hundreds of dead Varroa mites.

High mite drop can be a factor in colony collapse. I don't expect them to perform well next season - if they survive through the winter. I expect them to be weakened, and any brood raised in early spring will be heavily infected with Deformed Wing Virus or other diseases symptomatic of Varroosis.

I had hoped that the colony would be better able to manage Varroa. They've been untreated for a significant period of time. The swarm came last season from a feral hive in Barton.

Earlier this season they were very bad tempered which may be related. I should have checked whether they were Queen-Right (you bang the side of the hive. If the roar calms down quickly then they have a Queen. If not then they may be in distress and Queen-less).

I doubt whether replacing their Queen this year would have led to this situation. Even if she had no mite tolerance there would have been a time lag to produce vulnerable brood, and then a further lag to build up mite numbers. It seems more likely that this is the difference between mite resistant and mite tolerant. In the former there are hygenic behaviours or adaptations which inhibit Varroa mite reproduction. In the latter the bees just tough it out. I suspect that Hive E is only tolerant. We'll see whether it is tolerant enough.

Deformed Wing Virus appears to be seasonal in Hive A

Submitted by will on Wed, 31/05/2017 - 06:40

For at least the last 2 years I have observed a definite pattern in Hive A. In spring there are lots of crawling bees outside the hive. Some are clearly affected by Deformed Wing Virus (DWV); others maybe by another paralysis virus or by exhaustion.

They crawl around near the hive. If you launch them into the air they fall back to earth. They never make it back to the hive and have probably been ejected by the other bees. The Sparrows eat some of them. The others presumably die out of site.

By mid-May they have all disappeared. Mite drop on the hive floor has diminished so much that I've started wondering whether Ants are removing them.

I don't have an explanation. Maybe there is greater transmission of viruses when the bees are confined to the hive during the early spring build up. Maybe these bees have been in the hive for a while and are only ejected in spring.

I'm going to write to a DWV researcher to ask whether seasonal expression of DWV and other diseases is usual, and if she has an explanation.

Joining the ReViVe project

Submitted by will on Thu, 02/06/2016 - 19:32

BBKA News ran an article in June about a new project to study Deformed Wing Virus in untreated hives: the ReViVe project*. This is part of Professor S. Martin's research group in University of Salford.

I contacted the PhD student who is undertaking the study and offered my two new hives. These have come from a feral swarm and have not been treated or controlled for Varroa.

The two hives are now part of that study. I have sample tubes to fill with bees for testing. I'm wondering how to persuade the live bees into the tubes. It's going to be tricky.

* Rolling out the Evolution of resistance to Varroa and DWV