Tennessee: Ryegrass Is a Big Problem, What Should You Do?

Ryegrass in emerged corn. Photo: University of Tennessee

Ryegrass in emerged corn. Photo: University of Tennessee

Clearly, one weed many have had trouble with in 2016 is ryegrass.  Questions began a couple months ago and continue today. 

They have ranged from tactics to burn ryegrass down before planting to how to control it in a standing corn crop and more recently, where did all that ryegrass come from that is in my wheat? 

When it comes to burning down ryegrass before planting, it is abundantly clear that glyphosate is no longer effective.  Adding clethodim in with the glyphosate has been the most effective way to control ryegrass in a burndown.  We need to remember this for 2017.

The question on how to control ryegrass in a standing corn crop really has no “sure fire” answer. If the corn hybrid is Liberty Link then Liberty at a quart rate can be effective.  Of course, the bad thing about utilizing Liberty in corn applications in March and April is that air temperatures are often too cold for Liberty to be effective. 

In order to get the best ryegrass control with Liberty, try to pick a warm spell where temperatures are in the mid-80s and apply it during the middle of the day.  The other option is Steadfast Q which can be effective on ryegrass even at cold temperatures. 

The catch is that some ryegrass in the state is ALS-resistant so Steadfast Q will not be effective in those cases.

The most recent question has been why do I have so much ryegrass in my wheat?  The answer is that ryegrass continues to develop resistance to our POST- applied ryegrass herbicides. 

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We lost Hoelon years ago and more recently we confirmed ALS-resistant ryegrass, which has quietly been spreading across the state.  In those cases herbicides like Finesse, Powerflex and Osprey are no longer effective either. 

Because of this many moved to Axial and now we are starting to see ryegrass in these fields as well.  Ryegrass has been confirmed resistant to Axial in Arkansas and it would not be a surprise to find it in Tennessee.   

We are in the process of testing this year.

This all leads me to my main point for the 2016/2017 wheat crop.  We are going to have to rely much more heavily in wheat on delayed PRE applications of either Zidua or Axiom this fall.

We have seen the most consistent ryegrass control with Zidua at 1.5 ozs/A or Axiom at 8 ozs/A when used delayed PRE. Then follow up with Axial, Osprey, Powerflex or Finesse as needed.