Potential Herbicide Carryover Needs to be Considered before Planting Wheat. It was not uncommon last year for fomesafen (Flexstar, Rhythm, Dawn, Prefix and Reflex) applications in mid-summer to carry in and injure wheat. According to the label, four months must pass between a fomesafen application and planting wheat this fall. The highest probability of carryover is in fields that have seen little rain this summer. This is another ramification of managing glyphosate resistant Palmer amaranth.
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 herbicide applications 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. 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. Finesse has been used in Tennessee for about three years now and has for the most part worked well. Of course, like all pres, it works best when it receives a rain 7 to 10 days after application to activate it. 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 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. In cases where it was a problem it became 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 Sencor at 3 to 4 oz/A post emergence over the wheat that is at 2 to 4 lf. This timing of a Sencor application has been a very inexpensive way to manage bluegrass and just establishing broadleaf weeds like henbit.
Ryegrass Control. When it comes to ryegrass control, some type of two pass approach works best. It can either be a pre followed by a post or two post applications. One reason for this is that wheat is more susceptible to yield loss from ryegrass that emerges with it in the fall than ryegrass that emerges in the spring. Therefore a pre or early post application can remove that potential yield loss. Over the last several years we have had a fairly extensive flush of ryegrass in the spring. A post application is often required to clean this up. Finally, we have confirmed Osprey resistant ryegrass up in Dyer County this past year. Using a two pass program that utilizes two different modes of action will be the most sustainable method to manage ryegrass long term.
A few years ago we only had one option for ryegrass control in wheat and that was Hoelon. Now we have Osprey, Axial, Finesse Grass and Broadleaf and PowerFlex. Osprey has been the main “go to” herbicide the last several years and it has performed well particularly applied in the fall controlling ryegrass, many broadleaf winter annuals and even small bluegrass. It is applied at 4.75 oz/A with 0.5% NIS plus spray grade ammonium sulfate (AMS) or 32% nitrogen solution. Axial XL has also performed well controlling ryegrass. It will not provide any control of bluegrass or broadleaf weeds. Axial XL is a new formulation with the surfactant included that is to be applied at 16.4 oz/A. We looked at Finesse Grass and Broadleaf for the first time in 2008 and it has provided good control of ryegrass, broadleaf weeds and even some bluegrass. The rate for Finesse Grass and Broadleaf is 0.75 to 0.9 oz/A along with 0.25% NIS. STS soybeans must be used for double crop behind a Finesse Grass and Broadleaf application. PowerFlex, which first came on the scene in 2008, has performed very well in controlling ryegrass. It also has good activity on broadleaf weeds as well as wild garlic. It is weak on bluegrass.
One final point is that Axiom and Prowl H2O are good herbicides for bringing residual ryegrass control. Most importantly they use a different mode of action to control ryegrass compared to the herbicides mentioned above. We must start using some diverse modes of action in wheat if we are to keep rye grass from rapidly developing resistance to Axial, Osprey, PowerFlex and Finesse Grass and Broadleaf.
