The recommended time to treat with Fumidil-B for Nosema is in the fall,
two gallons or 2:1 syrup (sugar:water) with 1 tsp Fumidil-B per gallon.
 
Spring feeding for overwintered is less often recommended, but some
recommended a spring treatment of a gallon of 1:1 syrup with a tsp of
Fumidil-B.
 
The same spring treatment is recommended for packaged bees.
 
_The_Hive-and_the_Honey_BEE_ also cautions that treated bees on infected
equipment equals infected bees.  Treatment for infected equipment is
fumigation with acetic acid.  I can't quote time of treatment or
concentration of acid.  I really need an office library!
 
Aaron Morris - I think, therefore I bee!