Ryegrass Burndown And Control In Crop

JACKSON, TENN.

   Ryegrass control this time of year can be very challenging. Ryegrass is most easily controlled with glyphosate when it is very small or when it is headed out. Glyphosate will typically provide inconsistent control of ryegrass between these two stages. Some kind of two pass approach has provided the best ryegrass control in our research. Glyphosate applied early burndown followed by paraquat (Gramoxone Inteon) 10 days later has provided good control. Also, sequential applications of paraquat have also performed well particularly when one of the applications is tankmixed with a photo-system II inhibitor (PSII). In corn, a PSII inhibitor would be atrazine or Princep, while in cotton it would be Cotoran or Caparol, and in soybeans metribuzin.

   Of course some will not have time, particularly in corn, to use a sequential approach. Therefore, glyphosate tankmixed with a rimsulfuron (Basis, Resolve) product will provide the best chance of obtaining good weed control with one application. In corn, a follow-up application early post may be needed. In that case, one can use either Resolve Q or Accent Q alone or mixed in with glyphosate, which will typically provide good control.

   There is documented glyphosate-resistant ryegrass in Arkansas and Mississippi. To date, we have not found it in Tennessee. However, we have documented some ALS-resistant ryegrass in Dyer and Lake Counties this past year. I do not believe the ALS-resistant ryegrass is widespread as we still get good control with herbicides like Finesse, Opsrey and Powerflex in wheat across most of the state. However, for some of you in Dyer and Lake Counties, some of the options that include rimsulfuron or Accent mentioned above may provide inconsistent ryegrass control due to resistance. Δ

DR. LARRY STECKEL: Extension Weed Specialist, University of Tennessee