Oxalic Acid.

[Jon]

I just checked some trays below colonies which got oxalic 6 days ago and there were far more mites than I expected.
Normally when I apply Oxalic I might find a dozen or so mites but the 4 trays I looked at had up to 200 mites on each.
My best guess is that the cool weather late summer meant that the Apiguard was not as efficient as usual.
This could also explain why I have found that clusters are smaller than usual. More mites and virus produces shorter lived bees.

[fatshark]

Same here Jon. Apiguard mite fall (September) was really low, but I've now had a couple of consecutive days with about 100 mites dropped (National). I'm not sure whether it was inefficient Apiguard or just a period of extended brood rearing going into the autumn. I'm certainly not aware that the temperatures here were particularly low in September.

Another thing to worry about is my honey fudge has failed to set

[Black Comb]

Not boiled it (slowly) for long enough.

[saskia]

The guy from Aberdeen -Alan bowman gave a very good talk on gene knockdown the other day in Edinburgh one of the interesting things he said was that someone had looked at old museum s(?Victorian) samples of honey bees for viruses, and the ones we find we're mostly present but at orders of magnitude lower levels than found in presence of mite. I have often wondered about transmission of viruses in absence of mite- still not sure what it would be.. I had assumed not trophyllaxis -but don't know enough about viruses and how they multiply etc which cells they invade,and how thy effect bees..

[Jon]

Hi saskia
A paper which was published earlier this year by Martin et al looked at the arrival of varroa on some of the Hawaiian islands.
There are different variants of Deformed Wing Virus which occur naturally in bee populations but once the mite arrives, one type of DWV comes to predominate and unfortunately this is the variant of DWV which causes most damage to honeybees. There was a thread started on this earlier in the year.

[gavin]

As for the mechanisms maintaining the diverse DWV types at a low level without Varroa to vector them ..... I haven't a clue but there are people on this forum who have talked knowledgeably about such things and maybe they'll be along in a minute.

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[Black Comb]

So for colonies with the high mite count post oxalic what and when do you plan to treat with?

[Jon]

If you apply Oxalic in a broodless period it should get rid of the mites quite efficiently - but other than that a shook swarm in spring is one option.
I have used Apiguard in autumn followed by Oxalic in winter for several years now and it has worked for me without any other treatments being necessary.

[Black Comb]

Same here Jon but counts noticeably higher this year.
Shook swarm is favourite for me at the moment.

Anyone tried queen trapping?

[Calum]

Lactic acid at this time of year... 15%, 8ml sprayed per side of a frame full with bees Will use it on my shook swarms next summer to, too reduce the initial varroa infestation levels...