Allen Dick wrote:

> The evaporation method is cheap and simple, and apparently very effective.
> Even one application has effects lasting for weeks, apparently due to the
> vapour condensing to small crystals that endure for a while.

snip
> I think vaporized oxalic may be one.

Allan's website has info on Oxalic Acid and is one of the many I visited
trying to get info.

There are a variety of application methods and each has its own
concentrations and amounts. There are two drip methods, one you drip
between frames directly on the bees. The other you drip on the frames.

There are also a variety of foggers, vaporizers and sprayers. Some are
commercial, some are home made. You can make up a solution and use a
common garden sprayer. Or use a fogger. Or use a vaporizer.

All seem to have some things in common. They are very effective in
killing mites, but only exposed mites. You are usually looking at 70-90%
kills. More than one application is not recommended. Applications are
best in the fall, especially during the broodless period. Temperature at
the time of application is a not usually an issue, like formic or
menthol, so fall application is no problem. Plus, add on the usual
precautions for any pesticide.

It is easily obtained, since it is sold cheap in hardware stores for
bleaching wood. It is dangerous, but it is much less concentrated than
formic. Usually the concentrations are about 3-4%.

It is indiscriminate in what it kills in concentrations higher or
applications longer than what the application method calls for. You can
drip on the frames at a higher concentration than on the bees than
spraying than... you get the idea, so it is not one size fits all.

I have used it twice. The first time, about two years ago in spring, I
killed a weak hive. I used the concentrations sent by a beekeeper who
used it for several years. I eventually figured out that the directions
were for a strong or normal strength hive but there was nothing in the
directions to know that. I followed the directions to the letter and
lost the hive. Which is why I did a lot more research and found out that
there is were a span of concentrations and amounts to administer, as
found on the web, so be careful before you leap on the Oxalic Acid
bandwagon.

That said, I am using it. It works when applied correctly. It will not
give 100% control, but it does not appear to be anything that mites will
develop resistance to. It is easy to apply and only requires one visit
to the hives, but takes a bit longer than putting in strips. And you
have to be careful in what and how you do it.

My recent application (drip on frames) was uneventful and the bees show
no ill effects. But we shall see how they are in the spring.

Bill Truesdell
Bath, Maine