I came across this snip from an Eric Mussen newsletter from last spring 
again and thought it worth repeating.  The mention regarding Tactik was 
most interesting IMO.
---
1.) ...it is interesting to note what Zachary Huang's lab discovered 
(ABJ abstract #14) about feeding fumagillin to honey bees to control 
Nosema ceranae. In their studies, they found that the antibiotic impacts 
both the parasite and the protein makeup of the honey bee intestinal 
tract. In fact, as the level of fumagillin decreases in the bees over 
time, it reaches a low level which actually stimulates spore production 
of N. ceranae. A similar effect is seen with N. apis, but it is not 
nearly so pronounced._It could be that the low levels of fumagillin may 
be suppressing the honey bee immune system. The use of fumagillin as a 
last resort cancer treatment in mammals severely impairs their immune 
system. _
2.) Chris Mullin and his cooperators at Penn State University (ABJ 
Abstract #20) have been reverse-engineering some pesticide formulations 
and testing some of the common "inert ingredients" for honey bee 
toxicity. N-methylpyr-rolidone (NMP) was the first to be emphasized. The 
researchers found that NMP is toxic to honey bees, especially so for 
brood. With a bit of NMP in the commercial formulations, Bravo® was four 
times as toxic to brood as the active ingredient chlorothalonil is by 
itself. _Tactik®also was four times as toxic to brood as was straight 
Amitraz._ As I mentioned earlier, it is going to be very difficult to 
try to regulate pesticides based on potential danger to bees when so 
many inert ingredients and adjuvants are complicating the picture.

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