Italian Ryegrass Control Options
Herbicide-resistant Italian ryegrass is getting harder to control in Southern fields. There are still a few options available, but none are perfect to mitigate yield loss from the invasive grass.
"It's a big deal for farmers. It can be a bigger deal than Palmer (amaranth) pigweed, and there's not a lot of tools in the toolbox for it," Charlie Cahoon, a North Carolina State University (NCSU) Extension weed specialist, told attendees at the recent Mississippi State University Row Crop Short Course, in Starkville, Mississippi.
Italian ryegrass is distributed throughout the country, but the annual or biennial weed thrives in dark, rich soils in regions with mild climates.
Since the 1980s, control of Italian ryegrass has been more problematic as it slowly became resistant to five herbicide sites of action. These include: Group 1, ACCase inhibitors (Hoelon, Fusilade, etc.); Group 2, ALS inhibitors (Osprey, Accent, etc.); Group 9, EPSPS inhibitors (glyphosate); Group 10, glutamine synthetase inhibitors (glufosinate); and Group 15, long-chain fatty acid elongase inhibitors (Dual Magnum, Zidua, etc.).
Cahoon says paraquat, a Group 22 herbicide commonly sold as Gramoxone, has been the most consistent herbicide for burndown control of Italian ryegrass. "It's the last line of postemergence defense," he says. Cahoon also says farmers have reported instances of paraquat-resistant Italian ryegrass, which NCSU scientists recently confirmed.
Two applications of paraquat tank-mixed with another herbicide, such as atrazine for fields going into corn and metribuzin for fields planted to soybeans, will give farmers the best chance to kill emerged Italian ryegrass under 4 inches tall, Cahoon explains. High rates of paraquat may also be needed, he adds.
A combination of residual herbicides (Dual, Zidua, etc.) and cover crops can also control Italian ryegrass, he says, along with tillage.
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