New Pesticides Harming Bee Populations

Last week I had the pleasure of going to a lecture by Dave Goulson, Brittan’s James Bond of Bumblebee Conservation (though I may think this because he looks a bit like Daniel Craig and peppered all the usual slang into his talk including “bloody” and “jolly”). The theme of his presentation was neonicotinoids, a type of pesticide that is increasingly used in agriculture and home gardens, and has become increasingly controversial on the other side of the pond.  In fact, the EU just voted to ban them. But concern over this relatively new class of pesticides has been relatively non-existent in the US despite increasing evidence of the negative consequences of their use.

Neonicotinoids are derived from tobacco, but are terrifically toxic to invertebrates. A gram of the stuff is enough to deliver a lethal dose to 250,000 honey bees. This means that neonics are multiple times more deadly than DDT, the substance exposed in the now famous “silent spring.”

Neonics can be applied to crops in two ways: as a seed coat and a foliar spray. The seed coat is marketed to farmers and being less wasteful, but in truth, only 2% is absorbed by the plants, with the other 98% accumulating in the soil and ultimately entering waterways. The 2% that does enter the plants is systemic, meaning that it gets into all of the plant tissue, from the roots, to the leaves, to the pollen and nectar. And even the tiny amounts expressed in the nectar, when gathered by bees over time, can be lethal or cause decreases in hive productivity.

One of Dave’s students found that when bumblebee colonies reared next to canola treated with neonicotinoids contained many fewer bees than those reared without exposure to the pesticide. Plus bees that foraged in fields treated with neonicotinoids had a harder time finding their way home. Dave described it like this: if you were dropped off on your front porch when you were drunk, you’d easily find your way home; the same goes for if you were dropped off somewhere you know very well. But say you were dropped off in a place you’d never been, you might have a really hard time getting back. This is essentially what happens with bees that are exposed to neonicoitinods, which are neuro-toxins, thus impair the bees navigational abilities.

The use of neonicoitinoids has skyrocketed since they were first introduced by Bayer in 1994. At the same time, populations of bees, from honeybees to bumblebees, have declined rapidly, despite the fact that the EU has invested heavily in eco-agriculture programs that are designed to bolster on-farm biodiversity. Although an explicit link between the pesticide use and bee distress has yet to be explicitly linked, Goulson strongly suspects that neonicoidinoids are a likely culprit. With bees responsible for pollinating one out of every three bites of food we eat, are we willing to take the chance?

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