@Andersonhoney, thanks for the first hand info, good to hear it didn't set you back.
Still think a hell of a lot more could be learnt from the experience if it was know for sure what was the cause of the deaths.
Like you have said farmers need to do what they need to do but knowing exactly what they can do with the least negative impacts on bees would be hugely beneficial. If it was the roundup that was responsible then it goes against all the scientific evidence, knowing why it did under the circumstances would be very important. If it was the wetter then it would back up your stance that any spraying will kill bees but raises the question of what would have happened if a wetting agent wasn't used. Would the bees have been unharmed, is this what we should be pushing to farmers who do want to look after bees. Spray if you must with a low bee toxicity herbicide but don't use a wetter?
Chemical use in agriculture is a fact of life bee keepers need to live with, at the moment it appears the consensus seems to be you can have bees or you can spray you cant have both. It would be great if there was a way for farmers to continue spraying and have little impact on bees.