Overuse of herbicides costing UK economy £400 million a year

Weed resistance to herbicides is costing the UK’s economy as much as £400 million a year, according to scientists from the University of Sheffield and conservation charity the Zoological Society of London (ZSL).

Researchers from the University of Sheffield and ZSL’s Institute of Zoology explained the widespread use of herbicides is leading to resistant black-grass, which in turn, is costing UK millions in lost profit.

The study marks the first time experts have put an economic figure on the herbicidal resistance of black-grass, which is decimating winter wheat crops across the UK.

Heralded as western Europe’s most economically significant weed, black-grass can force farmers to abandon winter wheat, the UK’s main cereal crop.

It’s estimated to cost UK growers as much as 800,000t of lost wheat yields each year.

Growers have been using herbicides to try and tackle the problem, but in many areas of England, resistance is becoming an increasing problem.

Impact

Published in this month’s Nature Sustainability, researchers from the University of Sheffield, ZSL’s Institute of Zoology and Rothamsted University have devised a new model which helps quantify the economic costs of the resistant weed and its impact on yield under various farming scenarios.

An estimated four million tonnes of herbicides are applied to crops worldwide each year. There are 253 known herbicide-resistant weeds already, and unlike the known costs to the economy of human antibiotic resistance, estimates of the costs of resistance to agricultural chemicals are severely lacking.

Over-use of herbicides causes loss of wild plant diversity, damages insects and wildlife, and can lead to poor water quality.

Prof. Robert Freckleton, from the Institute for Sustainable Food at the University of Sheffield, said: “This research underlines the enormous costs that are incurred by farmers as a consequence of herbicide resistance.

Because there are few alternatives to the current range of herbicides, evolved resistance is only going to become more of a problem. This means that some crops will be uneconomical to grow in the future.

The research found the UK is losing 820,000t in wheat yield each year, roughly 5% of the UK’s domestic wheat consumption, due to black-grass.

If all fields were to contain large amounts of resistant black-grass, it is estimated this would result in an annual cost of £1 billion, with a wheat yield loss of 3.4 million tonnes a year.

Lead author and postdoctoral researcher at ZSL’s Institute of Zoology, Dr. Alexa Varah, said: “This study represents the first national-scale estimate of the economic costs and yield losses due to herbicide resistance, and the figure is shockingly higher than I think most would imagine.

We need to reduce pesticide use nationwide, which might mean introducing statutory limits on pesticide use, or support to farmers to encourage reduced use and adoption of alternative management strategies.

“Allocating public money for independent farm advisory services and research and development could help too.”

Ways forward

Management industry recommendations have so far advised using a mixture of herbicides, designed to prevent the evolution of specialist resistance.

However, recent research has revealed that this method actually leads to a more generalist resistance – and in some cases creates resistance to chemicals the plants have never been exposed to.

Glyphosate is now one of the few herbicides that black-grass has not evolved resistance to, with farmers now reliant on repeated applications to control the weed.

However, evidence from a recent study shows that resistance to glyphosate is now evolving in the field too.