#United States #Madison #Weed Science #Waterhemp #PPO Inhibitors

Understanding Waterhemp Resistance to PPO Inhibitors

Recent advancements published in the journal Weed Science shed light on a pressing issue for agricultural practices in the U.S. Midwest: the evolving resistance of waterhemp (Amaranthus tuberculatus) to protoporphyrinogen oxidase (PPO) inhibitors. This research, conducted at the University of Wisconsin-Madison, highlights that this resistance does not only develop from postemergence herbicide applications, as previously understood, but also from soil-applied preemergent treatments.

Background of the Research

The study, overseen by Dr. Rodrigo Werle, a prominent associate professor and weed scientist, focused on the effect of various PPO inhibitors, such as sulfentrazone, fomesafen, and flumioxazin, explicitly questioning how preemergence applications could contribute to resistance. This exploration was crucial, as resistance to herbicides significantly undermines the effectiveness of weed control strategies employed by farmers.

For years, the reliance on PPO inhibitors has been pivotal in managing waterhemp populations, especially those already resistant to other classes of herbicides. The historical perspective painted a stark image where postemergence applications correlated with resistance. The revelation that soil applications could trigger similar resistance challenges our understanding and strategies for using these essential herbicides.

Key Findings and Implications

The research documented the first confirmed case of waterhemp surviving PPO-inhibiting herbicides applied preemergence. This discovery is alarming because it constraints one of the few remaining effective methods for early-season weed management, afforded by these preemergence products. Given that waterhemp poses a significant challenge to many farmers in the Midwest, its resistance signals a critical turning point in weed management protocols.

As Dr. Werle noted, “This serves as an early warning to growers to diversify their weed management programs before similar resistance spreads.” Resistance at the preemergence level restricts the arsenal available to farmers, necessitating a reevaluation of existing strategies.

Recommendations for Farmers

To combat the rising tide of resistance, researchers suggest several strategies. Firstly, farmers should apply full-label rates of herbicides and mix PPO inhibitors with other effective preemergent herbicide classes. This method dilutes the risk associated with relying on a single mode of action, ensuring that the effectiveness of herbicides remains intact in the field.

Moreover, integrating non-chemical tactics such as crop rotation, cover cropping, and cultural or mechanical control strategies can further delay the emergence of resistance. Fostering a complex approach to weed management, rather than a simplified dependency on specific herbicides, is crucial.

Conclusion

The ongoing research into the resistance development in waterhemp outlines a vital juncture for agricultural practices. By understanding the dynamics of herbicide resistance, farmers and researchers can tailor more effective long-term management strategies. The full research article, discussing resistance to PPO inhibitors, can be found in the latest edition of Weed Science, escalating the conversation around integrated weed management practices.

Farmers, researchers, and stakeholders must pay heed to these findings to safeguard the efficacy of weed control measures and ensure sustainable agricultural productivity.