Hi Richard,
 
treating the bees in the early winter with "oxalic-acid" (don't now the correct
translation) is a new methode tested from University of Bologna (Italy) and also
tested at University of Hohenheim (Landesanstalt fuer Bienenkunde, Germany).
By dropping twice times an acid-sugared-waterliquid in proportions like
1kg suger:1l water:140gr (oxalacidihydrat?)to the closed bees, 50 ml per hive,
they measured a varroakilling efficiency of 96%. There are no beelosses because
of the acid observed.
The user should use protective glasses and gloves against the acidsmoke and
little sprinkels.
It's important by all acidmethodes.
 
Next wintertime i'll test it likewise.
 
Hans
(Germany)