Thanks E.t. I was trying to understand what you were taking from the discussion. I think you hit the nail on the head when you describe how the colonies can handle some levels, and when they reach certain point or stressor, its too much.
One thing I would add to the thought process is IMO the exposures are much lower and in some areas and crops non existent now, as opposed to pyrethroid spray.
For example here in the Midwest, Corn and beans are coated, Corn pollen is available roughly 2 weeks of the year, and a tiny amount of the forage is taken, Ohio university has research showing about 12% max for a 2 week period. Carry that out and your roughly .009% of the yearly pollen is contaminated at a level far below the LD value. Soybean nectar is usually even less. The rest of the season here we are clean. No arborist out spraying trees with foliars.....
If you add canola/rapeseed to the mix which I do,(traveled the bees to Oklahoma) it bumps up a bit to about 4% of the pollen (I take the honey so not sure if that counts) still the levels in that 4% are well below the LD 50 values.
So my potential exposure is still pretty low. And since all 3 crops are short duration, and well before winter, the bees have plenty of time to metabolize it.
Compare this to the alternative. The typical pre. Neonic regime was a in furrow pesticide Clouds of it around the planter just exactly like the planting dust issue, but on every machine not just air seeders. Followed by a post emergence Foliar spray, this of course got the crops and approximately 20 feet of the margins. For 3-5 days this dosage exceded the LD value, and was deadly, of course some got transported to hives, this treatment was usually repeated, just before canopy again. So 3 exposure events per field and margins, of an airborne pesticide that was lethal on contact for about 3 days (they claimed a week)
Canola in northern states was done this way, now, in most fields Foliar sprays are non existent for summer canola/rape the seed coating is usually enough.
Contrast that to sunflowers, commercial sunflowers don't bode well to systemic yet, and as a result are usually sprayed very heavy, while in bloom. I was talking to a guy in ND last night, he sharecrops 10,000 hives and some of that is in sunflowers. To say he has problems with them is an understatement. He was complaining a lot about the lack of pre spray calls he has been getting. Not about increased spraying as he is used to that but to the lack of human compassion in notifying him.
So for me in this area Neonics are a great help/ improvement. There may be more to the picture so we keep our eyes open.
The other thing to add is this is not always true. I was reading BC last month, a HORRID article on the problems in Greece, they had a invasive species and elected to do some foliar sprays of trees to stop them. The case in WA where it appears someone spray the trees at the mall, ETC. The problem is though, the usage, not the poison.
(as the article in BC it seems greenpeace wrote it, and to say they convoluted things is an understatement)
Charles
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