Ari wrote:
'Like Peter has said, oxalic is not helping if you have too many mites in
the fall when winter bees are developing.  That’s why we treat hives at this
point with formic or thymol. But we use only small dosages of these and don’
t get problems with dying brood from formic or large residues of thymol in
hive products. For example hives with 1 langstroth box are treated with
single treatment 10 g of thymol compared to Peters 4 times 8 g.'

The reason for using the four treatments of 8g at weekly intervals is to
allow a complete brood cycle to emerge and therefore kill the mites that
emerge from the cells.  One treatment of 10g may kill phoretic mites, but
this is of limited use if there are large numbers of mites in the brood
cells.  By treating through august, after the crop has been removed, I can
be sure that there is no risk of contaminating the crop and the colony will
be virtually free of mites throughout the rest of the autumn and winter;
this will enable it to rear a strong population of healthy young bees for
overwintering.

I agree wholeheartedly with Allen's "we need a toolbox full of different
miticides as well as genetic remedies..." and I would not like to be cast as
a champion for thymol to the exclusion of all other treatments but, to be
honest, I personally am not too keen on the alternatives available at
present (with the exception of the genetic option).
The synthetic pyrethroids contaminate wax very badly and will take many
years to eliminate from the wax pool.  Surely there are very few beekeepers
who are happy to introduce these substances into their hives?
Lactic acid and SOE are impractical for anyone with more than a very small
number of colonies.
Formic acid is very dangerous to handle, especially in the field away from
running water and medical help.  As Ari noted, '5 years ago many of us
thought that formic was the final answer, but it was not. All alternative
methods have larger variation in results than hard chemicals. When we raised
the amount of formic to the levels that were enough in almost all hives, we
started to see unwanted effects to bees'.
Oxalic acid is extremely poisonous (the acid should not be confused with
oxalates, which as is often quoted, are found naturally in spinach and
rhubarb) and colonies apparently do not tolerate multiple doses well -
severely limiting its usefulness as we have discussed.  Whilst I am happy
that the dripping method is reasonably safe both for bees and their keepers,
I have grave reservations about the other methods of application.  Spraying
suffers from the same drawbacks as lactic and SOE in terms of practicality
and, with the vaporisation methods, requires serious protective equipment
for the beekeeper and I still find it difficult to believe that there is
little or no contamination; spray must go into open cells and the
vaporisation method apparently coats everything inside the hive with oxalic
acid crystals.

Thymol crystals, on the other hand, are cheap, quick and easy to apply, do
not contaminate if used correctly, give excellent control without the need
for other treatments, are low-hazard for the bees and their keeper, do not
deteriorate in storage and do not cause resistance.  Until I find something
better, I intend to continue to use thymol exclusively.

Peter Edwards
[log in to unmask]
www.stratford-upon-avon.freeserve.co.uk/

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