>In my experience EFB does not go away by itself these days when forage
conditions improve or you requeen.  Most bees these days have some hygienic
traits due to mites and those bees remove diseased larva so fast in my
experience I do not see the classic symptoms of EFB such as discolored
larva.  All I see is empty cells which should have larva in them.

Dick, this is also my experience.  I often see spotty brood patterns,
suspect EFB, but may need to look through three or more brood combs to find
a single symptomatic larva.

On the other hand, in some hives I see raging infections with clearly
symptomatic larvae.

And yes, in answer to Peter's question, the simple test is to see whether a
12-day application of oxytet makes the problem disappear.  It invariably
does to every suspected case of EFB in my own operation.

In reply to Charlie's question of "what "prophylactic" really means?",
there is a clear definition--intended to prevent disease (as opposed to
treating observable disease).  In my own operation, I found that it is
generally more cost effective for me to put my money into better management
and supplemental feeding, rather than into prophylactic treatments.  That
said, three years ago I applied my first operation-wide prophylactic
treatment of oxytet in 15 years, due to seeomg a clear epidemic brewing in
my hives when I inspected them in January.  This prevented a serious
problem, and I have not needed to do it again.

Re Jerry's observation about the elevated rate of mortality in marked bees,
I often see this in scientific papers.  This leads me to believe that
unskilled lab assistants are often pretty stressful to those bees.


--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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