Jumpstart Italian ryegrass control in the fall
Italian ryegrass: Knock it down in the fall for an easier burndown in the spring. Extension weed scientists in Mississippi and Arkansas give recommendations for post-harvest ryegrass control, from application timings of the most effective residual herbicides.
At a Glance
- Ryegrass is a winter annual that comes up from seed each year.
- Two Midsouth Extension weed scientists say a fall residual herbicide application is the best way to get ahead of ryegrass.
- For fall herbicide applications, farmers should read the label and be aware of any plant-back intervals.
Italian ryegrass is a winter annual that begins to show up this time of year. Here in the Delta, there are not many options for spring burndown, and Extension weed scientists agree that fall is the best time to get ahead of the weed.
“Just like any other weed, the easiest time to control ryegrass is before it ever comes out of the ground,” said Jason Bond at Mississippi State University.
Ryegrass is an efficient annual, yet it does not have a large seedbank. Instead, ryegrass comes up from seed each year. Bob Scott, at the University of Arkansas System Division of Agriculture, said that around 99% of ryegrass seed comes up the following fall or winter when temperature and moisture are right for germination.
“Less than 1% to 2% of the ryegrass seed will last more than a year in the soil,” Scott said. “So, if you can do something in the fall to control that first flush of ryegrass, you can pretty much eliminate the problem. Or you can at least reduce it to the point where it is much easier to handle the next spring.”
Timing fall residuals
One problem many farmers face is herbicide resistant ryegrass. While the problem varies from state to state, it is worse in Mississippi. The best solution is to put out a fall residual before weeds have a chance to come up at all.
In the Delta, most row crop fields are prepped with a stale-seedbed. Bond said this tillage system is tailor made for residual herbicide applications. Then on years with cooperative weather, it is an especially good fit to maximize fall field prep and “start clean” in the spring.
Bond said, “The number of acres that get treated in the fall is dictated by weather, and we have had some good fall weather the last three years.”
Once the fields are prepped, timing is key for weed control. Bond said, later is better up to the point of being practical. He explained that while Dec. 1 would be the most ideal timing for a residual herbicide application, that scenario is unlikely based on historical weather patterns.
“Our recommendation is to check the 10-day forecast on Oct. 15. If there is no rain in sight, then wait,” Bond explained. However, if the forecast calls for a sizeable rain, then it is time to make those fall herbicide applications before a rain closes out your window of opportunity for the season.
Overall, timing depends on what is best for the individual operation. Bond said a lot of that has to do with how far along farmers are with harvest and where they stand with fall field prep.
Product selection for ryegrass control
When it comes to product selection, there are two main active ingredients to apply in the fall for ryegrass on row crop acres for corn, cotton, and soybeans. Bond said the first is metolachlor, and the second is Zidua.
Bond said, “Over the years, the active ingredient that hits more acres than any other for ryegrass has been metolachlor.”
There are many products with metolachlor as the active ingredient, and one most widely known is Dual Magnum. Another popular product is Boundary, which is a premix of metolachlor and metribuzin. Then there is Zidua and products that contain Zidua as the active ingredient.
However, none of these products can be used in fields where rice will be planted. Instead, for acres dedicated to rice, Bond said the only residual treatment for ryegrass is Command.
Scott reminded that it is important to read the product label and be aware of any plant-back intervals. “Some of these products have specific labels for the fall. Others simply have plant-back intervals for different crops.
“You have to read the label carefully, especially in some of those cases where the label may or may be specifically labeled for a fall application,” Scott said. “It is important to be aware of what you can and can’t plant back into.”
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