Had a look at the Danish beekeeping society's website www.biavl.dk today, in
the
Danish language part, press sygdom and then varroa. Here is a short
description
of 2 heat treatment boxes and a couple of photos

1) is the Borgstädter- Thermo-Box in which  capped frames are treated.
The treatment duration is 4 hours at 44 degrees C. It is stated that only
minor
damage occurs to the brood and there may be some shortening of the bee
lifespan.

100 % of the mites dies with this treatment.

2) is the Apitherm-skab (trademark) which is a box in which up to 18 frames
can be treated
at a time. It is stated that it is possible to keep the mites in check with
this
system only. Open brood cells will not survive the treatment for which
reason
treated frames should have mosly capped cells. A treatment takes 3 hours
where the temperature is raised slowly to just under 44 degrees C. With this
system
there is no damage to the bees and a shortening of the lifespan does not
occur.

Most of the mites dies with this treatment and the survivors presumably
becomes sterile.

With both systems it is possible to treat even during a honey flow.

It is also mentioned that some beekeepers have made the equipment
themselves.

What I would like to know is if anybody on the list know how the optimal
rise of
temperature is in system 2, does anybody have a graph showing the optimal
or recommended temperature rise over time. Should be fairly simple to make a
insulated box heated with a couple of lightbulbs, circulated air with a
small fan
and a baffle to keep direct heat from the frames.

The article on the website was written by Camilla J. Brødsgaard & Henrik
Hansen.

Best regards

Viktor in Ontario