Italian Ryegrass Control for No-Till Corn

Mark VanGessel, Extension Weed Specialist; mjv@udel.edu

Italian ryegrass is the same as annual ryegrass. The weed we struggle to control in wheat and barley is the same plant that is sometimes used as a cover crop. The same characteristics that make it a good cover crop are the same attributes that make it a pesky weed. Furthermore, it is the same species that has developed resistance to glyphosate and a number of other common herbicides.

Whether it was planted as a cover crop or there are scattered plants throughout the field, annual ryegrass can be troublesome to control in no-till corn. A trial for annual ryegrass control was conducted in 2009 at UD’s Research and Education Center. Treatments included glyphosate or Gramoxone Inteon and they were either applied alone, with atrazine, with Bicep II Magnum, with Resolve, or with Bicep II Magnum plus Resolve. Glyphosate control was about 85% control, but when tankmixed with atrazine or Bicep, control was reduced to 70 to 75% control. The addition of 1 oz of Resolve to glyphosate plus atrazine or glyphosate plus Bicep II Magnum increased annual ryegrass control to over 90%. The three-way mix of Gramoxone Inteon, Bicep II Magnum, and Resolve also provided over 90% control, and this was higher than any other combination with Gramoxone Inteon. Annual ryegrass (or Italian ryegrass) is difficult to control. The addition of Resolve improved ryegrass control. In our trial, corn planting was delayed at least 2 weeks after herbicide application and no injury from Resolve was observed.

Annual ryegrass should be sprayed early, 4 to 6 inches tall. Larger plants are more difficult to control and increase the likelihood of needing two herbicide applications to kill it.

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