Blog: A grown-up debate on neonicotinoids

Oilseed rape_600_405

Chris Hartfield_275_413

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It's encouraging to read a new study in Nature that focuses on both the impact of neonicotinoid use on food production as well as pollinators. The article, published last week, balances the positives of neonicotinoid use (the yield benefits and reduced use of foliar sprays) with the negatives (impacts on honeybees). This balance is rare where papers on neonicotinoids are concerned.

In terms of the positives, the study shows how using neonicotinoid seed treatments significantly reduces farmers’ use of foliar insecticide sprays. This is an important finding because, across a dataset covering about 73,000 ha, it shows how use of targeted seed treatments results in fewer pesticide sprays and in principle this should be better for the environment.

There’s currently significant interest in this year’s ‘neonicotinoid-free’ oilseed rape yields. This study importantly shows how neonicotinoid use results in yield increases. With a dataset covering 47,000 ha, this evidence shows clear and significant benefits to UK oilseed rape yields as a result of neonicotinoid use. The benefits aren’t in every single year, but enough to be convincing as to the value of using neonicotinoids. 

In terms of the negatives, it shows a correlation between use of imidacloprid seed treatment and honeybee colony losses. It predicts differences in colony loss of 10% between areas of low and high exposure to imidacloprid.

This is a correlation and doesn’t demonstrate causation. Put simply, the study shows links, but doesn’t show imidacloprid use actually caused honeybee losses. It’s like showing a link between a medicine and a dizzy side-effect, but not being able to show that every time dizziness happens it’s the medicine’s fault, because it could be caused by many things.

It’s also interesting the link involves imidacloprid and not the other neonicotinoids restricted by the EU. Imidacloprid is an older neonicotinoid and before the restrictions its use as an oilseed rape seed treatment had declined and less than 1% of the UK crop was treated with it.

Considering the study shows links but not causes, the researchers suggest large scale field based experiments are needed to determine real world impacts.

This is a well-balanced paper that leads us towards having a grown-up debate about the trade-offs between the food production benefits for society and negative environmental impacts of pesticide use.