The future of herbicides in farming

By Andi Anderson

Recent research shows that changing climate conditions are reducing the effectiveness of post-emergence (POST) herbicides used to manage agricultural weeds in crops like corn and soybeans.

A team of scientists from the USDA Agricultural Research Service and the University of Illinois Urbana-Champaign analyzed 30 years of data from 16 weed science programs across the U.S. Corn Belt, highlighting the impact of variable weather on three commonly used POST herbicides: fomesafen, glyphosate, and mesotrione.

The study revealed that temperature and precipitation patterns days before and after herbicide application significantly influence their effectiveness against major weeds, including waterhemp, giant foxtail, and morning-glory species.

Temperature extremes below 66°F or above 77°F were linked to reduced herbicide performance. Excessively warm conditions can accelerate weed growth, producing larger plants that are harder to kill, while hot weather after application can increase plant metabolism, neutralizing herbicides more quickly. Conversely, cold temperatures slow plant metabolism, limiting herbicide absorption and effectiveness.

Precipitation also plays a critical role. Dry conditions before application can thicken the waxy coating on leaves, making it harder for herbicides to penetrate. On the other hand, excessive rain after application can wash herbicides off leaves or stress plants, further reducing effectiveness. These findings emphasize the challenges growers face as climate change creates more unpredictable weather patterns.

The study also examined the combined use of glyphosate and fomesafen, which offered more consistent weed control under variable conditions. However, researchers caution that relying solely on POST herbicide combinations isn’t enough. They recommend integrating soil-applied herbicides and non-chemical methods to achieve better weed management.

The evolving adaptability of weeds, accelerated by climate change, adds urgency to the need for innovative solutions in weed science. According to experts, investing in new tools and strategies is critical to staying ahead of weed resistance and minimizing losses in crop yields. As climate change continues to affect farming practices, research and development efforts must intensify to ensure effective and sustainable weed control.

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