When I had my first hive, ten years ago, I noticed the occasional bee with
shrivelled wings. At the time, I knew nothing of bee viruses, and had no
idea of the significance. I did nothing about it, and the number of affected
bees did not increase. I treated the colony for mites in the autumn, and
thought nothing more about it. As I've learnt more about viruses, I've
wondered why it is that I see the odd colony like that one, which has a very few
bees infected with DWV, but never develops a widespread infection.
This spring, I had such a hive. I was worried about the varroa level, but
it was too cold to treat with Apiguard, and there was too much brood for
oxalic acid tricking to do much good. I decided to leave the colony until it
got warmer, and see what happened. It was building up fast, and I felt it
would keep ahead of the mites until midsummer at least.
Every time I inspected it, I would find one or two infected bees. By the
end of May, the broodnest filled both a standard National and a 14x12 box,
and there was a cluster of a dozen or so such bees underneath. At this point
I noticed that every one of these bees was black. It was a hybrid colony,
with half the bees having a yellow stripe. I couldn't find a single yellow
bee with shrivelled wings. Around midsummer, I requeened the hive, as its
temper became increasingly vile as it built up, and with close neighbours, I
couldn't risk keeping that queen.
The only way I can explain what I saw is to suppose that a single patriline
within the colony was particularly susceptible to DWV. That suggests that
my colonies probably have a range of susceptibility. I've suspected this
for several years, since I had an outbreak which destroyed one colony, while
leaving others in the same apiary with survivable levels of infection. From
now on, I'm going to requeen any colony in which I find a single bee with
DVW. I don't know how much progress I will be able to make, but I wonder
how much resistance can be bred into a strain.
Regards,
Robert Brenchley
Birmingham UK
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