Over the last ten years, Italian ryegrass has become an increasingly more significant issue throughout the Delta. This weed poses the potential for substantial yield loss in many crops grown throughout the region, especially corn. It is highly competitive with corn during the early portions of the growing season. If left uncontrolled, it can cause variations in emergence and a reduced rate of growth and development due to competition for sunlight and water/nutrients. A study evaluating Italian ryegrass termination timing in corn planting at Mississippi State University in 2017 and 2018 showed that the optimal termination time was three to four weeks before planting. This study also observed yield losses of 1.25 to 1.75 Bu./A. per day when Italian ryegrass control was delayed beyond three to four weeks (Wesley, 2019).

Controlling Italian ryegrass has grown increasingly more complex over time as it has become glyphosate-resistant (GR). Resistance was first found in Mississippi in 2005, followed by Arkansas in 2008, and Tennessee in 2012 (USB, 2022). Most Italian ryegrass populations are also resistant to the ALS-inhibiting herbicides. We still see some success with early spring applications of clethodim before Italian ryegrass progresses to tillering and stem elongation growth stages. With clethodim, growers need to be mindful of the 30-day plant back interval to corn that accompanies this herbicide. The most popular go-to burndown option is an application of paraquat when the Italian ryegrass has some size. For those early-season applications where we are experiencing cool and cloudy conditions, paraquat may not be as effective, and an additional application is often needed within 10 to 14 days.

Many growers in the region are now focusing on fall-applied burndowns for Italian ryegrass and tank mixing a residual herbicide with this pass. Most of the residuals used are Dual Magnum® (S-metolachlor), Zidua® (Pyroxasulfone), Boundary® (S-metolachlor + metribuzin), or Trifluralin. If adequate moisture is present after the fall application and the residual component is activated, additional control of Italian ryegrass and other winter annuals should be minimized in the spring months (USB, 2022).

If you aren’t approaching Italian ryegrass in this manner, we would advise taking note of those problematic acres and acres that will go to corn in the next cropping season. Make sure you emphasize those acres for fall-applied residuals for control of Italian ryegrass.

For assistance in creating a complete herbicide program specific to your weed spectrum, reach out to your local Beck’s representative. Always read and follow label directions.