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Weed Management Systems: Italian Ryegrass

Joan Campbell, University of Idaho

An initial Italian ryegrass survey was completed in 2006 and 2007 with 75 Italian ryegrass samples collected from Lewis, Latah, Nez Perce, and Benewah counties in Idaho and Whitman, Spokane, and Walla Walla counties in Washington. Italian ryegrass seed was collected again in 2017 to 2019 from the same areas and an additional 31 sites. Seeds from each sample along with a known susceptible biotype are screened in the greenhouse against herbicides used to control Italian ryegrass. Untreated plants are included from each sample. Screening has been ongoing and will be completed in May.

Post emergence herbicides tested in the second survey include glyphosate, Axial XL, clethodim, Poast, Assure II, Osprey, and PowerFlex HL. No Italian ryegrass samples were resistant to glyphosate. Diclofop is no longer used as Italian ryegrass had a high degree of resistance to this group 1 herbicide. Other group 1 herbicides increased from below 50% in the first survey to 58 to 75% resistance. Clethodim is the exception with resistance levels still below 25%. Screening of pre-emergence herbicides resulted in no sample resistant to Zidua or Outlook. Amber resistance is widespread at 86%. Axiom and Dual Magnum resistance is 25% and 14%, respectively.

Close attention to using herbicide resistant tactics will help keep herbicides effective for managing Italian ryegrass.

April 22, 2025
Probing our Country’s Soil Health
A reminder that there is a new nation-wide project called “Probing Our Country’s Soil Health”. It is being funded by the Natural Resource Conservation Service (NRCS). A major goal of the project is to build a national soil health database and new and improved tools for benchmarking and interpreting soil health metrics. The anonymous data will be used to expand a new and exciting tool called the Soil Health Assessment Protocol and Evaluation (or SHAPE). This tool helps provide better references for farmers seeking to understand and build soil health. Idaho growers are encouraged to join this important initiative to help shape the future of soil health practices across the nation. More information can be found here!
April 22, 2025
FDA’s New Definitions of ‘Healthy’ Foods Takes Effect Soon - Here’s What you Need to Know
The FDA has updated its definition of the term “healthy” on food labels, with new rules taking effect on April 28, 2025. Under the revised guidelines, foods must contain a certain amount from a recommended food group—such as fruits, vegetables, whole grains, dairy, or proteins—and meet strict limits on added sugars, saturated fat, and sodium. The new definition also introduces important terms like Food Group Equivalent (FGE) and Reference Amount Customarily Consumed (RACC) to help standardize serving sizes. Labeling a product as “healthy” remains voluntary, but companies that choose to use the term must maintain documentation to prove compliance.
April 22, 2025
U.S. Considers Adjusting Port Fee Plan for Chinese Vessels After Pushback
The Trump administration is considering softening its proposed port fees on China-linked ships after receiving widespread backlash from U.S. industries, including agriculture, that warned of severe economic harm. The original plan proposed fees up to $3 million per port call to curb China’s maritime influence and boost U.S. shipbuilding. However, due to concerns that the fees could disrupt commodity shipping and strain businesses reliant on Chinese-built vessels, alternatives under review include delayed implementation, tonnage-based charges, or fees scaled to the proportion of Chinese-built ships in a company’s fleet.
April 22, 2025
USDA Scientist Asks Bigger Weed Questions
USDA research weed scientist Olivia Landau is asking big questions about the future of weed management in wheat farming. As part of the Pacific Northwest Herbicide Resistance Initiative, Landau focuses on identifying herbicide-resistant weed populations and exploring innovative approaches to manage them. As growers face increasing herbicide resistance, Landau encourages them to reach out and share field observations that might inform her research. She’s committed to making complex scientific information clear and accessible, helping the region’s farmers find sustainable, forward-looking solutions to weed management.
April 22, 2025
USDA Terminates University of Idaho Grant to Help Farmers
The University of Idaho’s largest grant, nearly $59 million from the USDA’s Partnerships for Climate-Smart Commodities (PCSC) program, was terminated due to new USDA criteria requiring 65% of funds go directly to producers. The original proposal had over 50% allocated for producer payments, with the remainder for technical and marketing support. The university had already begun enrolling producers and offering support to help them adopt sustainable practices. The USDA is relaunching the program as the Advancing Markets for Producers (AMP) Initiative, and U of I plans to revise and resubmit its proposal.