Economic cost of herbicide overuse

February 2020: Similarly to the overuse of antibiotics in humans, the overuse of herbicides is leading to resistance in weeds. In turn, this reduces crop yields with risks for food security, availability and pricing. A National Action Plan that supports farmers in transitioning to integrated pest management practices may address the challenge.

Information

UK farmers frequently apply high doses of herbicides to reduce the growth of weeds - such as black grass - to protect yields of winter cereals. Black grass out-competes wheat for soil nutrients and reduces the number wheat plants where it grows. Similar to the overuse of antibiotics, the practice of extensively applying agricultural herbicides has led to many weeds becoming resistant. Researchers have modelled the economic cost of resistant weed and its impact on UK yields under various farming scenarios. It projects that resistant weeds cause and annual economic cost of £400 million, corresponding to 800,000 tonnes of lost wheat per year.

Implications and opportunities

The study identifies that weed resistance will continue to grow under current farming practices. This may decrease effectiveness of herbicides, in turn, decreasing cereal yields and leading to lost income and crops with implications for UK food security, availability, and pricing. In addition, the overuse of herbicides can lead to lower water quality, loss of biodiversity, indirect damage to surrounding invertebrates, birds, and mammals. The paper recommends an introduction of statutory limits on pesticide use and calls for a National Action Plan that harmonises economic, agricultural, environmental, and health needs. In addition, the paper highlights the importance of supporting farmers in transitioning to alternative and more integrated pest management strategies. This could be achieved by means of public money, advisory services, and education to incentivise more diverse crop rotations, cultural control measures, direct sowing, regular monitoring, delayed drilling to allow stale seed beds, and strict field hygiene measures.

Limitations

The study explores the use of UK herbicides and results should be seen within their geographic context. Further research will be needed to explore the economic cost and impacts of overusing herbicides outside a UK context.

Sources

Varah, A., Ahodo, K., Coutts, S. R., Hicks, H. L., Comont, D., Crook, L., … Norris, K. (2019). The costs of human-induced evolution in an agricultural system. Nature Sustainability. doi:10.1038/s41893-019-0450-8 

The Telegraph. (2020). Black grass is threatening wheat crops after growing resistant to herbicide, scientists warn. Retrieved from https://www.telegraph.co.uk/news/2019/12/23/uks-food-security-threatened-herbicide-resistant-black-grass/