Published on Monday, March 6, 2017
God willing, planters will be rolling through fields within the next four to five weeks. If you haven’t already, now is the time to start thinking about burndown options. We’ve had a very mild winter (as you can tell by the size of our wheat!) and many winter annuals have grown much larger than usual. This should be taken into consideration when thinking about those hard-to-control winter weeds like Italian ryegrass and marestail.
Italian ryegrass has become consistently more difficult to control over the past few years as some of the populations have gained resistance to glyphosate. If you’re planning on planting soybeans, this shouldn’t cause any problems as there are options to control the weed once your crop has emerged. One such option is graminicide, (the most commonly used is Select Max® or clethodim), which offers farmers the ability to kill any glyphosate resistant Italian ryegrass that may have escaped the burndown in-season. Those who are truly affected by this weed are farmers looking to plant corn into a field that’s infested with glyphosate resistant Italian ryegrass. While clethodim is still the “go-to” herbicide for this situation, there is a plant-back interval (PBI) that you should be aware of. The labeled rate of Clethodim requires a 30-day waiting period before you can plant corn. Therefore, if you are planning on planting corn the first two weeks or April and you have ryegrass issues, you should start spraying within the next week.
Marestail (or horseweed) is probably the most difficult weed to control early in the season throughout our area. This weed can have resistance to multiple modes of action, including glyphosate and FirstRate®. While Dicamba has been the “go-to” herbicide for controlling marestail for many years, the release of dicamba-tolerant crops has left many farmers wanting to save their yearly allotments (maximum of 2 lb./A.) for at planting or in-season use.
In such a case, farmers can look to use Sharpen®, 2,4-D, or Gramoxone alone or in combination. I’ve seen farmers gain good control of marestail when mixing 1 oz. of Sharpen with 16 oz. of 2,4-D (4 lb. material). Keep in mind that the PBI for that rate of 2,4-D is seven days, and the addition of methylated seed oil (MSO) is required. A second option would be the use of Verdict® in combination with 2,4-D or dicamba. This has provided excellent control of marestail in the past, but again an extended PBI and the addition of MSO should be considered. Finally, the use of gramoxone can be used as another burndown option. If you decide to go this route, I recommend that you include a PSII inhibitor like metribuzin to help increase the weed control. Gramoxone by itself can flash burn weeds very quickly, which means it doesn’t really have time to fully get in the plant. The addition of metribuzin can actually slow that flash down and increase the efficacy of the herbicide. It also adds some residual control of other troublesome weeds like Palmer amaranth.
Timeliness is paramount when controlling any troublesome weeds, and cool-season annuals like Italian ryegrass and marestail are no exception. There are many different options when it comes to weed control so don’t hesitate to contact myself or your local Beck’s representative for more information.
Sharpen® and Verdict® are registered trademarks of BASF. FirstRate® is a registered trademark of Dow. Select Max® is a registered trademark of Valent.
Author: Austin Scott
Categories: Agronomy, Kentucky, Tennessee
Tags: Agronomy, Herbicide, Marestail, Austin Scott, Kentucky Agronomy, Tennessee Agronomy, burndown, Dicamba, AgChat, Italian Ryegrass, graminicide, horseweed