Weed control in wheat has become more of a struggle in recent years. This is due to several reasons including that more wheat is following corn where volunteer RR corn can be an issue, Poa has become more of a weed problem in wheat and herbicide resistance development in ryegrass.
Volunteer Roundup Ready Corn Management. There have been several calls about burning down volunteer Roundup Ready corn before wheat planting. In our research there have only been two herbicides that controlled the volunteer corn. One was 40- 48 oz/A of Gramoxone Inteon applied with 0.25% NIS at 15 gal/A. Coverage and rate are critical to make this work. Applying Gramoxone before 9:00 a.m. or after 5:00 p.m. will also improve the control this herbicide will provide. The other option was to use 0.5 oz/A of Finesse which also did a good job plus it provides residual control of ryegrass and many broadleaf weeds. Of course, like all PREs, it works best when it receives a rain within 7 to 10 days after application to activate. However, if it does not get an activating rain, the weed control can be inconsistent. One thing to remember is if Finesse is used, only STS or Bolt soybeans can be planted for double crop in the summer.
Bluegrass Control in Wheat. Bluegrass (aka Poa) can be a serious issue in some wheat fields especially if it becomes established before or with the wheat. If Poa becomes established with the wheat it can deter tillering and readily compete for nitrogen. Typically one of the best ways to manage bluegrass is to start clean. Using either tillage or Gramoxone Inteon at 40 oz/A will be a good way to manage this pest. Still another option is to apply metribuzin at 2 oz/A POST emergence over the wheat that is at 2 to 4 lf. This timing of a metribuzin application has been a very inexpensive way to manage bluegrass and very small broadleaf weeds like henbit.
Ryegrass Control. Ryegrass resistance to ALS-inhibiting herbicides (Osprey, PowerFlex and Finesse Grass and Broadleaf) has become a fairly common problem across Tennessee. Therefore Axial has increasingly been used for ryegrass POST. Unfortunately Axial in some counties this past year has also become less effective on ryegrass. The best way to control ryegrass that cannot be controlled with these herbicides is to use a delayed PRE application of Zidua or Axiom.