For decades, farmers have been using herbicides to kill weeds and grow healthier, more abundant crops. However, what may seem to be sound common practice is, after all, a growing concern for food security. 

 

Herbicides started to be used in the 40s. Seen as the best cure for malicious weeds, these chemicals have been globally used in agricultural practice. While there’s debate about the problems these may pose to people’s health, a less popular talk goes around herbicide resistance.

Herbicide resistance is a phenomenon that happens in weeds. When farmers use herbicides, they often spray them across crops. While most weeds die, a small number of them survive – they resist the herbicide. Soon these plants multiply and pass on such ability to further generations. This leads to resistant weeds, which cannot be controlled by any herbicide. This is a similar scenario to antibiotic resistance. In both cases, overusing a product leads to its inefficiency. 

If farmers cannot control weeds with herbicides, then these can quickly multiply and endanger entire crops. In the UK, black-grass, a type of weed, is already causing damage. Recent research shows that farmers lose 0.82 million tonnes of wheat due to black-grass annually. This is the weight of around 63 000 buses. This significant wheat loss is also costly to farmers. Scientists estimate that resistant black-grass costs 380 million pounds per year on lost gross profit. 

Black-grass is the most common resistant weed in the UK: 20 000 farmers already have it. Yet, other plants such as rye-grass, wild-oats, chickweed, poppies and mayweed have also started becoming resistant.

Chickweed is one of many weeds developing herbicide resistance.

What are the solutions?

Even though industries are now keen on creating new herbicides, resistance is inevitable. Sooner or later, weeds develop mechanisms of resistance and multiply, making new chemicals a band-aid solution.

So, if new herbicides cannot solve this problem, what could?

Using multiple approaches to tackle weeds is the most recommended practice. This is called Integrated Weed Management and encompasses different strategies from mechanical removal of unwanted plants to changing the type of crop each year. These strategies aim to replace herbicides with non-chemical solutions.

Even though non-chemical solutions are vital to stop resistance (or at least slow it down), ditching herbicides is still challenging. These products are cost-effective and easier to use when compared to non-chemical approaches. So, ditching these “miracle” solutions takes more time than one may expect.

The United Nations have predicted population growth of 2 billion in the next 30 years. Even though COVID-19 will probably influence these numbers, facts do not change – the world’s population is expected to increase. With more people, comes higher demands for food. In times in which both climate change and herbicide resistance threaten food security, ditching herbicides may soon stop being a difficult choice and become an essential need.

 

This article was written as a part of a project to raise awareness of herbicide resistance. You can read more about this project here.

 

References and Notes:

 

1- Varah et al., The costs of human-induced evolution in an agricultural system

2- https://www.iru.org/sites/default/files/2016-01/en-nea-bus-2007.pdf

3- https://media.ahdb.org.uk/media/Default/Imported%20Publication%20Docs/AHDB%20Cereals%20&%20Oilseeds/Weeds/WRAG/Maps%20of%20the%20distribution%20of%20herbicide%20resistant%20weeds%20in%20the%20UK%20(2016).pdf

4- https://www.un.org/development/desa/en/news/population/world-population-prospects-2019.html

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