Weedy rice outsmarts herbicides in US fields

Herbicide resistance rises in southeastern weedy rice

The battle against weedy rice in the southeastern United States is becoming increasingly challenging as these pests gain resistance to critical herbicides.

This concerning trend was highlighted in a study by Washington University in St. Louis, showing significant resistance developments in weedy rice.

The research, led by postdoctoral fellow Marshall Wedger, found that 57% of weedy rice samples from Arkansas, Missouri, and Louisiana had developed resistance to the IMI herbicides by 2022. A further 3.5% of samples were resistant to another herbicide class only used since 2018.

"We find that, at least for now, individual fields have their own compositions of weedy rice in terms of strain makeup and herbicide resistance, which makes management harder," said Wedger. His study reflects the intricate and evolving challenge that weedy rice poses to effective crop management.

Initially, herbicide-resistant rice varieties like Clearfield offered a solution to manage weedy rice, but as resistance spread, these solutions became less effective. "It’s similar to antibiotics in medicine," commented Wedger. "When resistance becomes widespread, we move on to another antibiotic. It’s less that Clearfield failed and more that its lifespan ran its course."

The economic toll of weedy rice is stark, with annual losses reaching $45 million in the US. This study serves as a crucial reminder of the dynamic nature of agricultural pests and the ongoing need for innovation in pest management strategies.

Farmers and scientists must continue to collaborate on developing new approaches to outpace the rapid adaptation of pests like weedy rice, ensuring the sustainability of rice production and the broader agricultural economy.