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  • Varroa population explosion

  • Honeybee pests and diseases.
Honeybee pests and diseases.
 #2981  by Jim Norfolk
 09 May 2019, 10:58
Just when you think you are beginning to understand how to deal with Varroa along comes a surprise.

I have two colonies one I started last year and the other split from the original, later in the year. Both were treated with Apigaurd in August and oxalic acid vapourisation in December. Mite drops after treatment were what I would call typical. My original colony has dropped the odd mite since, however the newer colony suddenly started dropping around 10 mites a day at the end of March, which I assumed to be a the result of a mite invasion from a robbed out dead colony somewhere nearby. Previous experience down south led me to believe that as the spring advances Varroa numbers drop, so I didn't treat. However this one went into overdrive with daily mite drops soon over 20 and heading for 30. Icing sugar dusting confirmed we had a problem. The next step was oxalic acid vapourisation. So off with the supers and in with the Varrox. The first treatment dropped over 300 mites in the first 24 hours and over 800 within the week. I applied a second dose of OA and have over 600 drop in the first day. I am guessing but the total mite population must be several thousand and I will keep going with the OA treatments until mite numbers have dropped right down. The question is why does one colony not have a problem and another a few feet away gets overwhelmed. Is it this particular colony which are not very good at defending themselves or I have the bees picked up a local strain of fast breeding mites?
 #2986  by NigelP
 09 May 2019, 11:50
Jim , I have had the same happen myself. I had 2 hives out of 10 in the garden a couple of years back which gave huge mite drops and needed repeated OA vaporisation errhum apibioxal (x10 at 5 day intervals) to get numbers down. One was headed by an F1 Buckfast and the other was a pure(ish) Amm queen.
I 'm flummoxed as to why this happens. to an odd hive here and there.
Randy Oliver also mentions it, saying some hives are mite bombs and he has no rational explanation for it.
Your suggestion that one colony is robbing a varroa infected feral colony is plausible, but it would mean they were the sole hive in your garden that had found it....which is possible.
 #2989  by Patrick
 09 May 2019, 13:48
NigelP wrote:
09 May 2019, 11:50
Your suggestion that one colony is robbing a varroa infected feral colony is plausible, but it would mean they were the sole hive in your garden that had found it....which is possible.
I have seen this explanation for single colony high mite counts despite treatment, frequently repeated before. I have no scientific rationale or evidence why some colonies / varroa are a) more resistant to treatment b) susceptible to varroa c) something else, but I find this convenient explanation for treatment "failure"as the sudden discovery of a mystery feral die out somewhere else apparently scuppering the otherwise infallible treatment intuitively less credible.

I suspect you are unusual Jim in being so thorough about counting / noticing high mite drops - I suggest most people only notice at the point of collapse or indeed after - another "mystery die out. Not a very helpful contribution I admit as I don't know why either, but something tells me the reason is closer to home and much more common than we realise.
 #2990  by AdamD
 09 May 2019, 14:35
I think it possible that one hive found a robbed another and the second hive just didn't locate it.

An example is that a few years back during August, I recall, I had one colony that brought home some very dark and strong honeydew honey - several frames of it - the other colonies in the same apiary had none.