By Andi Anderson
A research team led by the USDA Agricultural Research Service and the University of Illinois Urbana-Champaign has confirmed that changing weather patterns affect the effectiveness of post-emergence (POST) herbicides.
Building on earlier findings about soil-applied herbicides, the team analyzed a 30-year database from 16 weed science programs across the U.S. Corn Belt. They found that variable weather conditions significantly reduce the effectiveness of three commonly used POST herbicides—fomesafen, glyphosate, and mesotrione—against major weeds that impact corn and soybean crops.
The study revealed that weather, including air temperature and precipitation, plays a crucial role in herbicide effectiveness not only in the hours after application but also days before and after. The researchers noted that extreme temperatures, either below 66°F or above 77°F, reduced the effectiveness of these herbicides on weeds like waterhemp, giant foxtail, and morning-glory. Although the dataset did not explain why weeds were less responsive under these conditions, previous studies offer some insights.
“Weather doesn’t just matter in the hours after POST application, as other studies have shown. Our analysis showed air temperature and precipitation were linked with herbicide effectiveness days before and after application for the products and weeds we studied,” said Chris Landau, postdoctoral researcher for USDA-ARS and first author on the paper. “With the sheer amount of data we analyzed — thousands and thousands of data points, including a broad range of weather conditions over 30 years — we were able to characterize the effects of weather on POST herbicide efficacy on a much broader range of environments than previous studies.”
The findings are important because inadequate weed control due to ineffective herbicides can lead to reduced crop yields, threatening food security. The research highlights the need for farmers to adapt their weed management strategies in response to climate variability, ensuring that herbicides remain effective under changing environmental conditions. This study provides a broader understanding of how weather impacts herbicide performance, offering valuable information for future agricultural practices.
Photo Credit: usda
Categories: Illinois, Crops, Soybeans