Herbicide-tolerant crops can be a part of integrated weed management

The adoption of herbicide-tolerant crops and their associated agronomic practices can facilitate effective weed management, overcome growing problems with herbicide resistance in weeds, and help prevent environmental issues associated with the intensification of agriculture. 

However, several factors may limit the integration of herbicide-tolerant crops and their related farm management practices in integrated weed management systems. European scientists therefore propose five actions to facilitate the incorporation of herbicide-tolerant crops in integrated weed management systems in the European Union. They base their recommendations on experience gained in countries where herbicide-tolerant crops – either conventionally bred or genetically modified – are widely grown. 

IPM is necessary

Conventionally bred  and genetically modified herbicide-tolerant crops have changed weed management practices and made an important contribution to the global production of some commodity crops. However, farm management practices associated with the cultivation of herbicide-tolerant crops can further deplete farmland biodiversity and accelerate the evolution of herbicide-resistant weeds. 

Diversification in crop systems and weed management practices can enhance farmland biodiversity, and reduce the risk of weeds evolving herbicide resistance. Herbicide-tolerant crops are therefore most effective and sustainable as a component of integrated weed management systems. 

Treat herbicide-tolerant crops equally

Cultivation of crops with conventionally bred herbicide-tolerant traits presents similar weed management challenges and agronomic risks as crops with genetically modified herbicide-tolerant traits. However, the EU regulatory framework distinguishes between conventionally bred herbicide-tolerant and genetically modified herbicide-tolerant crops. All genetically modified herbicide-tolerant crops are regulated while conventionally bred herbicide-tolerant crops are not. 

This is paradoxical because the cultivation of herbicide-tolerant crops in North and South America has clearly revealed that the most severe environmental problems resulting from their cultivation are primarily related to agronomic factors, particularly herbicide-use practices, rather than genetic or biological factors. In other words, they present similar advantages and disadvantages. Conventionally bred herbicide-tolerant and genetically modified herbicide-tolerant cultivars therefore require the same diverse management strategies to address environmental issues. 

Five actions proposed

Integrated weed management advocates the use of multiple effective strategies and tactics to manage weed populations in a manner that is economically and environmentally sound. In practice, however, the potential benefits of integrated weed management with herbicide-tolerant crops are seldom realized because a wide range of technical and socio-economic factors hamper the transition to integrated weed management. 

Effective weed management without herbicide use is not presently conceivable in regular intensive farming systems. Herbicide diversity is therefore a key to weed control. In the long-term, cropping systems that are more diverse and less reliant on herbicides have to be adopted by famers to mitigate the risk of weed resistance evolution. 

Although such sustainable practices may be more costly for growers to implement in the short-term, they will be beneficial in the longer term, especially if appropriate policies and incentives are put in place. Such policies and incentives should include the following five actions: 

1 Education programmes to maintain and improve knowledge of weeds and their management

2 Revision of current stewardship programmes

3 Integration of socio-economic studies to understand and change growers’ attitudes and behaviour

4 Development of adequate public policy

5 Regulatory revisions 

You can read the article Integrated weed management systems with herbicide-tolerant crops in the European Union: lessons learnt from home and abroad in the scientific journal Critical Reviews in Biotechnology.