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Controversial pesticides increase pest numbers

Calls for a ban on neonicotinoid pesticides have been strengthened after a new field study, by Penn State and the University of South Florida, reveals that a neonicotinoid pesticide used to protect crops from insect damage can actually reduce crop yield by elevating slug damage.

The researchers found that slugs eating thiamethoxam treated soya crops weren’t affected by the chemical. However when the poisoned live slugs were fed to ground beetles, over 60% of the beetles were either incapacitated or killed. Ground beetles eat slugs, and with these important predators gone, the number of slugs exploded, ate more of the soya and reduced yields by 5%.

Slugs are a particular risk in no-till agriculture that leaves stubble on the surface when the next year’s crop in planted.  No-till farming has increased rapidly in the UK in the last decade.

Vanessa Amaral-Rogers, Buglife’s Campaigns Officer said “Whilst thiamethoxam isn’t supposed to control slugs, it’s concerning that a pesticide can actually cause an increase of other pests. Putting food on the table depends on crop pollinators and crop predators – the natural pesticide – this alarming result indicates that we must take the effects of artificial pesticides on all types of beneficial insect into account before we allow their use”.

The study add to a growing controversy about the effectiveness of neonicotinoids, repeatedly published scientific studies have failed to show that they provide consistent or even frequent yield benefits.  

Thiamethoxam is one of three neonicotinoids that were restricted last year by the EU due to their impact on pollinating insects such as honeybees.  However, neonicotinoids continue to be very widely used on wheat and other crops, despite mounting evidence of severe negative effects on aquatic life, birds and crop predators.

Matt Shardlow, Buglife CEO said “This is a horror story, neonicotinoids have been sold to farmers as an ‘insurance policy’, but in a no-till system, predators are imperative to keeping pest populations low.  We must understand how these chemicals came to be so widely used when their benefits are illusive”.

Buglife also want the Government to ask the Competition and Markets Authority to undertake a review of the extent of commission based selling in the pesticides sector, the vulnerability of the market to distortion and restricted consumer choice, the prevalence of miss-selling and the effects on vulnerable farmers and the environment.

 

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