What is in this article?:
- ALS-resistant barnyardgrass in rice
- What happens now?
• Two samples of barnyardgrass from Mississippi are most likely resistant to Newpath herbicides.
• Over 70 percent of rice acres in Mississippi this year were planted to Clearfield varieties or hybrids.
• Barnyardgrass can be manage in rice, even if it is resistant to Newpath.
• Programs must be developed around residual herbicides.
What happens now?
So what happens now? I tell people to manage barnyardgrass in rice just like Palmer amaranth in row crops. Like Palmer amaranth, barnyardgrass is much easier to control before it comes out of the ground. The Clearfield technology, similar to Roundup Ready, has let us become somewhat careless with herbicide timing. Too many times, barnyardgrass is sprayed in the three- to four-leaf stage (or tillering) rather than the one- to two-leaf stage. This may work some of the time with some herbicides, but it will not work all of the time. You cannot spray barnyardgrass too early. Get on it early and stay on it until the field is flooded. That is the only way to ensure you will have a clean crop in August.
Whether you are growing Clearfield or conventional rice, I think any barnyardgrass control program should begin with Command at planting. Over-the-top programs should contain tank-mixtures of postemergence and residual herbicides with multiple modes of action.
For instance, the first over-the-top application could include propanil plus Bolero (or RiceBeaux) or Facet. If you are in an area with a history of propanil resistance, then Ricestar HT plus Facet or Prowl H2O would be an alternative.
Every year I do a study on barnyardgrass control without using ALS (Newpath, Regiment, Grasp) or ACCase (Ricestar HT, Clincher) herbicides. Our best treatments have at least two applications of a residual herbicide, one of which goes out either pre-emergence or delayed-pre-emergence. The barnyardgrass pressure was severe in my rice plots at Stoneville this year. The only plots that I have right now that are completely free of barnyardgrass received at least two postemergence applications following a full rate of Command (1.33 pints per acre for my soil type).
Barnyardgrass can be managed in rice, even if it is resistant to Newpath. However, programs must be built around residual herbicides. When barnyardgrass does emerge, the timing of the postemergence herbicide is critical. With these postemergence applications, you should always use premixes or tank-mixtures of herbicides with multiple modes of action to reduce the pressure on the few chemistries available that are active against barnyardgrass.
At every rice meeting, I remind growers that there are no new barnyardgrass herbicides on the way. Since I have been at Stoneville, no company has asked me to test a new herbicide with activity on barnyardgrass. The current herbicides with barnyardgrass activity are the herbicides we will rely on in 2015 and 2016.
So, with that in mind, protect the herbicides and technologies that are in place in 2010. There are still some effective herbicides for barnyardgrass, but it is everyone’s responsibility to help prolong the effectiveness of these products.