The Economist, 31 March 2012
Climate change, habitat destruction, a paralysing virus, fungal infection and even a plague of parasitic mites have all been proposed. But one of the leading ideas is that the bees are suffering from the effects of neonicotinoids, a class of commonly used pesticides, introduced in the 1990s, which are toxic to insects but much less so to mammals.
All of the doses of imidacloprid, both high and low, that Dr Whitehorn gave her bees were “sublethal”—in other words, insufficient to kill the insects outright. Firms that produce pesticides, and the authorities that regulate them, are aware of the importance of bees to food production, and new products must be tested to make sure they are not fatal to helpful insects. But Dr Whitehorn found that even non-lethal doses of pesticide were bad for bees…
Moreover, even if it did not do so alone, it could be a contributing factor. Many researchers believe the label “colony collapse disorder” covers a multitude of problems; that would account for the long list of possible causes. But neonicotinoids have the explanatory virtue of being a fairly recent development and also one which, as these two pieces of work suggest, could be a common factor in weakening a colony without actually pushing it over the edge. The killer blow would then be administered by something else: a mite infestation, perhaps, or a fungal infection, or whatever else happened to turn up that a healthy hive would have shrugged off.
Recall of course that if we are going to expand the current model of agriculture, the one that has so far fed far more people than had ever been thought possible, we are going to need more and better pesticides, not less. Trying to produce more food, for more people is going to continue to push up against various limiting factors.