Oxford Bees

Deformed Wing Virus

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




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







Joining the ReViVe project





* Rolling out the Evolution of resistance to Varroa and DWV