The size of the chemical blitz bees face in fields

Not-so-mellow-yellowOwen Humphreys/PA

Perhaps I was naive, but when I discovered the extent of the chemical soup applied to typical fields I was astonished. As part of our ongoing investigations into the impact of pesticides on bees, we looked at 25 fields containing winter rapeseed or winter wheat during the 2012-13 growing season. For any particular field, the list of pesticides applied is worryingly long.

These are perfectly normal farms; not especially intensive, situated on the edge of the South Downs in East Sussex, an area of gentle hills, hedgerows and wooded valleys. Beautiful, rural England – Constable would have liked it here. But let’s look at it with a bee’s perspective rather than a painter’s eye.

Let’s look at one fairly typical field. The rapeseed crop, whose flowers the bees will feed on in season, is sown in late summer with a seed dressing containing the insecticide thiamethoxam. This is a systemic neonicotinoid, with exceedingly high toxicity to bees. Taken up into the plant, detectable levels will be in the nectar and pollen the bees gather.

In November, despite the protection supposedly offered by the neonicotinoid seed dressing the crop is sprayed with another insecticide, the endearingly named Gandalf. What harm could the wise old wizard possibly do? Gandalf contains beta-cyfluthrin, a pyrethroid. Pyrethroids are highly toxic to bees and other insects – killing insects is their job, after all – but as there should be no bees about in November that shouldn’t be a problem.

The following May, while flowering, the crop is sprayed with another pyrethroid, alpha-cypermethrin. Only weeks later the crop is blitzed with three more pyrethroids just for good measure – a real belt-and-braces approach. Why use one when three will do? The crop is still flowering at this point (it was a late year), and will be crawling with foraging bumblebees, hoverflies and other pollinators.

Between winter and summer, the crop is also treated with a barrage of herbicides, fungicides, molluscicides and fertilisers – 22 different chemicals in total. Most may have little toxicity to bees in themselves, but some, such as a group of fungicides (demethylation inhibiting or DMI fungicides), are known to interact with both neonicotinoids and pyrethroids, increasing their toxicity to bees.

So, when the fungicide prothioconazole is added to the mix tank that includes the year’s final application of chemicals, any feeding bee will be simultaneously exposed to a barrage of three pyrethroids, the thiamethoxam from the seed casing now in the nectar and pollen, and a fungicide that amplifies the toxicity of all these chemicals.

While farmers, agrochemical companies and food distributors say they haven’t a clue why bees are dying off at extinction levels.


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