I don't doubt or question the toxicity of neonicotinoids in bees or other insects.The toxicity of neonics will be "re-discovered" after many-many deaths... -cerezha
I do question how long neonicotinoids persist in the soil and in plants. Aphids feeding on crops that have been planted with seed treatments or soil treatments of neonicotinoids show no effects to their populations four to six weeks after planting. This class of insecticides is intended to target piercing-sucking insects (such as aphids) more than other insects, and the systemic action of the pesticides should target them nicely. I've done the counts of aphids on the two groups -- treated and not -- and can confirm that no difference exists in the populations and population growths on both soybeans and corn treated with neonicotinoids at planting. I've counted aphids on both from early July through September here.
I question how much field exposure bees actually face in most years from neonicotinoids. Bees here do not seem to collect much pollen in corn, and I've rarely encountered large numbers of bees in corn fields in the last several years (despite spending thousands of hours in corn fields sampling insect populations of various species). I've never observed bees around here collecting guttation fluids from corn; that doesn't mean that it doesn't happen, but I doubt it's common here.
And I question whether even a strong correlation between neonicotinoid exposure and CCD exists. That seems to be the central thesis in this thread, yet I'm not convinced that such a correlation exists. Even that Harvard study that was linked in Randy Oliver's review demonstrated that the bees in the treated hives died in January and February. Now, I have not seen CCD in person, but I thought the losses occurred in the fall (a.k.a, "fall dwindling?") rather than in the winter? And I thought a suite of other symptoms also characterized CCD?