Herbicide resistance and tackling the challenge of sustainable food production

By Bárbara Pinho, MSc Science Communication Student, University of Sheffield

The sustainable production of food is a challenge yet to be accomplished. Agriculture uses 70% of all fresh water and produces a third of all greenhouse gas emissions, as well as leads to biodiversity loss and soil degradation.

Producing food sustainably is a challenge we must tackle in order to feed the generations to come. According to the United Nations, the world population is expected to reach an astonishing 9.7 billion by 2050. Putting it simply, more people means more mouths to feed in the future.

However, with no new land to explore, increased urbanisation and a rising sea level (which reduces land availability), growing food to feed almost 10 billion people is far from an easy task. This is where science may be of help.

For decades, scientific research has been developing tools and strategies to grow increasing amounts of food in shorter periods of time. One particular discovery revolutionised how farmers grow food worldwide: herbicides.

Research and herbicides

When herbicides were created amid the Second World War, they provided farmers with cost-effective and quick methods to kill invasive species, commonly known as weeds. However, as years went by, these chemicals stopped being as effective due to a process called herbicide resistance.

Weeds that are exposed to the same type of herbicides, sooner or later, resist said herbicides. They can resist due to genetic alterations (such as mutations) or multiple molecular strategies to counteract a herbicide mode of action. This ultimately leads to weeds surviving and damaging entire crops while jeopardising yield production.

This is a global issue. At the time of writing, there were 262 species resistant to herbicides worldwide. In the UK, 20,000 farms have resistant black-grass, the most common weed in the UK. This is estimated to cause the loss of 0.82 million tonnes of wheat which in turn costs £0.38 billion in lost income to farmers.

These costs are not limited to just farmers though. If we don’t find solutions to guarantee a stable wheat production, we may eventually experience price spikes in certain products. In addition to this, the consequences of herbicide resistance threaten achieving the objective of feeding almost 10 billion people by 2050. What was already difficult, just got considerably more complicated.

Solving herbicide resistance

To address this issue, current research is exploring multiple strategies. At the University of Sheffield, Professor Robert Freckleton, who teaches Population Biology, described herbicide resistance as a “very difficult” issue to solve:

“It may be that the evolution of resistance to herbicides – or any biocide including antibiotics, fungicides, insecticides or cancer drugs – is inevitable.”

Most research at the University of Sheffield has been focusing on gauging the impact of herbicide resistance on farmers.

The Black-Grass Resistance Initiative

Wheat in fieldBetween 2014 and 2017, researchers from Sheffield together with other academics from Rothamsted Research, the Zoological Society of London, Newcastle University and the University of York launched the Black-Grass Resistance Initiative.

Among other goals, this project aimed to “unravel herbicide resistance in black-grass from gene to field”.

Through this project, the researchers were aiming to understand how some resistance mechanisms develop in weeds.

They also monitored black-grass in fields and interviewed farmers to design new management strategies to tackle resistant weeds.

In addition, this research estimated how herbicide resistance impacts both the economy and the environment.

These impact assessments lead the multi-institutional team to develop new management strategies in conjunction with farmers. The suggestions were mainly designed to delay herbicide resistance, through non-chemical techniques, as Professor Freckleton later explained:

“The best tactic is to slow or delay [herbicide resistance] and that can be done by relying on a diversity of control tactics. ‘Cultural control’ includes using tillage, crop rotation and other forms of weed control. Vigilance with monitoring and testing is important though. In many cases, it is too late to do anything by the time the problem has emerged and got out of hand.”

Crop science and new herbicides

While the obvious solution to tackle herbicide resistance would be to use fewer herbicides, this may be an unrealistic scenario. Farmers have been using herbicides and pesticides for decades to grow more food, as fast as possible. While it would be ideal to stop using chemicals in farming practice, Professor Ari Sadanandom from Durham University doesn’t think it’s feasible to ask that of farmers:

“I don’t think [stopping the use of herbicides] is a good way of moving forward; otherwise, how could you control weeds? Unless you clear all the soil of all the weed seeds, it’s not plausible, I think.”

At Durham University, research to bring solutions that tackle herbicide resistance reaches many different areas.

“Some people are working on fundamental plant science involving crops and they could generate new solutions. Other researchers are working with barley whilst others are working on cold stress and heat stress. The knowledge they get from these tests could be used to control weeds. The Chemistry Department is also working with new herbicides and focusing on making new products,” described Professor Sadanandom.

His research is more focused on studying fungal diseases in crops via cell biology. Still, he believes this to be a transferable area into herbicide-resistant yields. “I may start working with black-grass in the future because we may be able to bring some techniques that we’ve learned in the fungicide resistance world.”

Whether it be through new management strategies or making new herbicides, research is playing a key role in tackling a major threat to food security.

If we’re to feed 9.7 billion people by 2050 and even more in the decades to come, new strategies and techniques to complement farming practice may soon become the norm for farmers worldwide.

This blog was written as part of ‘The Path of Leaf Resistance’ project, which aims to raise awareness of herbicide resistance. Both this blog and the website are part of an MSc in Science Communication project conducted by Bárbara Pinho and supervised by Professor Robert Freckleton at the University of Sheffield.

All data collected for the project will serve the purpose of research on public engagement with the topic of herbicide resistance. This YouTube video has been created as part of the project to raise awareness and develop understanding of the issue of herbicide resistance.

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