Varroa

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Cathryn

Joined: 16 Jul 2005
Posts: 19856
Location: Ceredigion

Posted: Thu Sep 18, 14 6:34 am Post subject: Varroa

One of my friends has circulated a warning as he has seen an unexpected rise in the numbers of varroa. Possibly not that surprising, if bees have done well this year then so must their parasites. I've not yet checked my hives but I have been doing some reading on the effectiveness of dusting with icing sugar and the only research based work I can find says it doesn't appear to have any real effect.

Can anyone highlight some different research work on this?

Lorrainelovesplants

Joined: 13 Oct 2006
Posts: 6521
Location: Dordogne

Posted: Thu Sep 18, 14 6:48 am Post subject:

The icing sugar thing really depends on whether your bees self groom.

Ive started using a correx tray(wiped with a smear of veg oil) during season, and use it to check the number of mites. In the aftermath of dusting with icing sugar Ive noticed much more mites - therefore my bees are grooming - therefore its working.

I also use varroa gard dusted as a treatment before using apigard at end of season.

Cathryn

Joined: 16 Jul 2005
Posts: 19856
Location: Ceredigion

Posted: Thu Sep 18, 14 6:57 am Post subject:
I understand the principle but this, for example, is similar to most of the conclusions that I have read. https://www.ent.uga.edu/bees/personnel/documents/RevisitingPowderedSugar-JAR51414.pdf

Lorrainelovesplants

Joined: 13 Oct 2006
Posts: 6521
Location: Dordogne

Posted: Thu Sep 18, 14 7:03 am Post subject:
There is anecdotal evidence that not all honey bees groom. There is some specific breeding in West Cornwall to encourage self grooming bees - perhaps Tavascarrow has more info on this?

joanne

Joined: 28 Oct 2004
Posts: 7100
Location: Morecambe, Lancashire

Posted: Thu Sep 18, 14 8:52 am Post subject:

When I had my bee's they groomed as I would get a bigger drop after dusting.

However if you are in topbars or Warr� or any of the other alternative hive methods, the likelihood that you've got significant numbers of varroa decreases as the bee's are self determining the size of the brood cells by instinct they tend to make smaller cells which means the varroa doesn't breed in the same way as they can't co-habit during bee development.

I have always worked on the principle that less is more and tended to go for a thymol treatment in Autumn rather than sticking loads of icing sugar all over my bee's

Tavascarow

Joined: 06 Aug 2006
Posts: 8407
Location: South Cornwall

Posted: Fri Sep 19, 14 1:26 pm Post subject:

Most conventional beekeepers use oxalic acid in the winter &/or thymol in the spring & autumn, they only use icing sugar as a monitoring tool. There is no doubt that it has an effect, but whether that is sufficient to cure a badly infested colony is doubtful IMHO.
If your bees have a degree of resistance anyway then regular icing sugar treatments might be sufficient, only trial & close monitoring will answer that.
So my advice would be use it, keep an eye on the number of varroa dropping & the general health of the colony & be prepared to use something stronger if needs be.

dangerous

Joined: 01 Feb 2010
Posts: 27

Posted: Mon Oct 13, 14 6:05 pm Post subject: Re: Varroa

Cathryn wrote:

One of my friends has circulated a warning as he has seen an unexpected rise in the numbers of varroa.

Infestation in large established colonies is very significant this year according to NBU.
Beware of relying on natural mite drop or the Beebase varroa calculator as indicators of numbers of mites.
One of my colonies on 14 x 12 with a natural drop of less than 5 a day in September, when brood numbers are decreasing and you would expect a higher proportion of phoretic mites, has dropped approximately 4,000 mites during three weeks of Apilife. Many of my friends are reporting similar.
As an aside there is little to support the protective effects of sugar dusting and small cell size.
Varroa was not a problem last year...many have become complacent.
A good ongoing IPM which can include sugar dusting/drone culling/chemical control should keep on top of things.

Cathryn

Joined: 16 Jul 2005
Posts: 19856
Location: Ceredigion

Posted: Mon Oct 13, 14 6:45 pm Post subject:
That's worrying although mine are new colonies. The bee inspector visited just after I had removed a varroa board with very little on it. He was happy with what he saw and I didn't do another treatment. I hope he was right.

Mistress Rose

Joined: 21 Jul 2011
Posts: 16005

Posted: Tue Oct 14, 14 6:32 am Post subject:
The mild winter last year probably didn't help.

dangerous

Joined: 01 Feb 2010
Posts: 27

Posted: Wed Oct 15, 14 4:27 pm Post subject:
I will oxalic in the winter to mop up. I'm looking into vaporising which looks much less "upsetting" for the bees than opening up and dousing them with syrup.

Cathryn

Joined: 16 Jul 2005
Posts: 19856
Location: Ceredigion

Posted: Fri Feb 06, 15 12:41 pm Post subject:
Well I've just treated mine with oxalic acid. I didn't disturb them much, those in the topbar barely noticed me. Maybe as I become more confident I will treat them differently but for now I am thrilled that they are doing well. I did put fondant on them a month or so ago which has been more or less ignored by those in the topbar. Clearly I am overwintering several mice though.

sean
Downsizer Moderator

Joined: 28 Oct 2004
Posts: 42219
Location: North Devon

Posted: Fri Feb 06, 15 12:48 pm Post subject:
They're probably ones from your house using it as a holiday cottage.

Cathryn

Joined: 16 Jul 2005
Posts: 19856
Location: Ceredigion

Posted: Fri Feb 06, 15 1:40 pm Post subject:
Well, touch wood and all that...

Mistress Rose

Joined: 21 Jul 2011
Posts: 16005

Posted: Sat Feb 07, 15 12:55 pm Post subject:
I don't know much about top bar hives, but in 'conventional' hives it is usual to put a mouse guard on the entrance in the autumn. My stop your little friends using it as a winter holiday cottage.

Tavascarow

Joined: 06 Aug 2006
Posts: 8407
Location: South Cornwall

Posted: Sun Feb 08, 15 3:27 pm Post subject:
You may find the bees will have killed them by spring. I haven't treated any hives since last spring. They where hail & hearty at the end of the summer so I will treat with thymol once the weather has warmed.

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