The scenario of herbicide-resistant weeds: Management challenges and perspectives

The evolution of herbicide-resistant (HR) weeds is becoming a challenge for sustainable food production. As of March 2023, 267 weed species have been confirmed resistant to one or more herbicides globally. The objectives of this review were to summarize the status of herbicide-resistant weeds, their mechanisms of resistance, herbicide resistance dispersal mechanisms, management options, and future perspectives on herbicide-resistant weeds. Target site resistance (TSR) and non-target site resistance (NTSR) are two mechanisms for the evolution of HR weeds. TSR results from changes in the specific target site/enzyme for the herbicide, whereas NTSR includes physiological processes that reduce herbicide concentration at the target site. Once an individual weed evolves resistance, the resistance can disseminate through seed-mediated gene flow, pollen-mediated gene flow, or vegetative propagules. Widespread dispersion of HR weeds threatens crop production, and effective steps need to be taken to restrict this dispersion. A widespread occurrence of HR weeds, particularly in developed countries, requires a systemwide, integrated, holistic approach for their effective management that can reduce reliance on herbicides and integrate non-chemical control techniques, including cultural practices, cover crops, conservation tillage and residue retention, harvest weed seed control, and mechanical weed control. Multiple herbicide-resistant crops and herbicide premixes with multiple sites of action are widely used for HR weed management; however, their long-term sustainability is questionable. Moreover, new herbicides with novel site of action and other non-chemical weed management strategies need to be developed that can be adopted by growers. Thus, management of herbicide-resistant weeds is complex and requires a multidisciplinary approach.