Varroa floors are widely used in Germany for monitoring the
mite population and to determine the effect of treatments.
A number of studies have led to the following rules of thumb:
 
Time: June/July (in Germany!, heavily breeding colonies)
number of mites in the colony = natural daily mite fall x 120
 
The natural daily mite fall can be estimated from the total
number of mites on the varroa floor (whole surface under the colony,
or apply a suitable correction factor) divided by the number
of days the floors were in (without any special varroa treatment!).
The floors should be in place for at least 10 days to obtain
valuable estimates. The natural daily mite fall should not exceed
5 - 10 mites, otherwise it is recommended to treat with
e.g. formic acid, of course, without honey supers on.
 
Time: October (Germany!, poorly breeding colonies)
number of mites in the colony = natural daily mite fall x 500
 
Again, the number of days the floors are in place should be
at least 10 days. The natural daily mite fall should not
exceed 0.5 - 1 mite, otherwise treatment is recommended.
 
This second mite population estimate is necessary because
the mite population can be heavily influenced at this time
of the season by mites hitchhicking on drifting or robbing bees.
 
Michael
--
Michael Haberl
Hessische Landesanstalt fuer Tierzucht, Abt. Bienenzucht
Erlenstr. 9, 35274 Kirchhain, Germany, 51n 9w
Tel: ++49-6422-9406-12
Fax: ++49-6422-9406-33
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