What are some good options to control ryegrass with a short turnaround to plant back to corn? When addressing this question we have to realize that some of this ryegrass is likely glyphosate-resistant (GR). Though we do not have it officially confirmed at this point, I am confident from the last couple years' field observations that Tennessee does have a few fields with glyphosate-resistant ryegrass.
My experience with ryegrass is that even if it is not full-blown resistant, it is typically difficult to control with glyphosate, so some non-glyphosate options are needed. When it comes to recommendations on managing GR ryegrass, I turn to my colleague at Mississippi State University, Jason Bond, who has been studying this weed for some time.
Bond’s primary recommendation for spring control is sequential applications of Gramoxone at 40 to 48 oz/A spaced about 10 days apart. Though I have not been a fan of the long and cold winter, it has helped us with respect to ryegrass control. It has kept it relatively small for this time of year to where Gramoxone should provide good control. Moreover, Gramoxone will provide good control of even our GR poa.
The other often asked question is what about clethodim (Select) for ryegrass control before corn planting. There is a supplemental label for Select Max to be used for burndown before corn planting. Select Max maybe applied at 6 oz/A and corn can be planted 6 days after application. Many folks went this route in their corn burndown last year and it worked more consistently than glyphosate alone on ryegrass and poa.
However, for the full-blown GR ryegrass that has plagued Mississippi for several years, 6 oz/A of Select Max is not enough. They typically have to go with much higher rates on ryegrass in Mississippi and as such must wait 30 days before planting corn. Fortunately, our Tennessee ryegrass population is not as bulletproof to glyphosate yet and a tankmix of glyphosate and 6 oz/A of Select Max has worked well.