On Fri, 5 Oct 2007 08:44:54 -0700, randy oliver <[log in to unmask]> wrote:

>There are various anecdotal recommendations going around.  Medhat Nasr
>suggests that some are at far too high a concentration.  He recommends using
>the product about double strength.  The label suggests 1:1 syrup, but
>beekeepers prefer 2:1.  The recommended rate is 1 lb (454g) Fumagilin to
>45gal heavy syrup.  Dribble 4 oz per colony, or up to 8 oz for strong
>colonies.  Repeat after a week.

Just to expand on both Randy and Bob's good posts, the label recommends that
one jar Fumagilin-B covers 50 wintering colonies.   One jar (454g) contains
9.5 g of fumagillin active. 

Label dose ~ 190 mg fumagillin active per colony.

Following this spray recommendation, the dose per colony is 8oz (0.230 L) x
9.5g fumagillin/170L (45 gal) x 2 weekly treatments = 26mg fumagillin active
per colony. 

Consequently the spray treatment would have to be ~7 times more effective
than the syrup treatment to still be effective.  While it is possible that
this mode of application is more effective I know of no study that supports
this claim.  A dose roughly twice this spray recommendation (42 mg/colony)
was applied in spring sugar dust in a study at Beaverlodge in the 1980s and
colonies still maintained infections of about 4 million spores/bee 1 and 3
weeks following treatment.  Furthermore, a number of older studies suggest
that bulk feeding at 190 mg/colony in the fall is the smallest dose you can
get away with before efficacy begins to drop off.

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