Ryegrass, Ryegrass, Ryegrass!
DR. LARRY STECKEL AND HAYDEN LOVE
JACKSON, TENNESSEE
Planting is well underway! Unfortunately, ryegrass is still present in some fields. Our research has shown this spring that tankmixes of clethodim + glyphosate (Picture 1), Sharpen + glyphosate and Reviton + glyphosate have been the most consistent ryegrass options.
On the other hand, a few reports from the field have not found as consistent control of ryegrass with those options as our research would suggest. The most resent greenhouse screen conducted by Hayden Love on 17 ryegrass populations from West Tennessee probably gives the best explanation for the inconsistent control in some fields.
First, the greenhouse screen found that 12% of the ryegrass populations are highly resistant to clethodim and glyphosate. As such in the few fields where the clethodim + glyphosate tankmix have failed, resistance to those herbicides is likely the cause.
Second, the greenhouse screen also showed that the ryegrass in the state is a segregating population with respect to glyphosate resistance. Of the 17 populations tested, 2 were very susceptible to glyphosate and two were highly resistant. The other 13 populations had glyphosate-resistance levels somewhere in between these two extremes. As such, a tankmix of 1 oz of Sharpen or Reviton likely bumps up the control glyphosate can provide for those ryegrass populations with more marginal glyphosate resistance (2 to 3x) but is not enough for populations with more robust resistance. In those cases, higher rates of Sharpen or Reviton would likely improve control.
Please remember increasing the Sharpen rate to 1.5 oz/A increases the plant back to soybean to 14 days. Increasing the Reviton rate to 2 oz/A pushes the plant back to soybean to 7 days.
Ryegrass that has escaped earlier burndowns is typically harder to control. Paraquat typically provides the best chance of success to take out ryegrass recovering from earlier burndown.
Once the crop has emerged, options to control ryegrass are much more limited. Liberty applied from 10:00 a.m. to 3:00 p.m. on a hot and humid day is the best option in corn. In soybean, Liberty tankmixed with clethodim has performed fairly well. ∆
DR. LARRY STECKEL AND HAYDEN LOVE
UNIVERSITY OF TENNESSEE