If not managed, resistant Italian ryegrass could become a problem similar to glyphosate-resistant Palmer amaranth or pigweed in the Mid-South and Southeast.
Texas AgriLife Extension integrated pest management specialist Jim Swart, who works out of Commerce, Texas, and covers the Northeast corner of the state, says most wheat farmers in the area have avoided the problem, but in fields where resistant ryegrass has taken hold, it’s becoming more troublesome.
He’s looking for answers. This fall he seeded some demonstration trials to identify the best solutions. In one test area, he used ryegrass seed collected from a field heavily infested with resistant ryegrass. “We may have created a monster,” he said. “But this is what we need to help growers.”
Problems are most severe in fields where wheat has been planted year after year with no rotation. In some of those fields farmers have seen control with Axial XL herbicide begin to break down. “About 75 percent of our growers say they have seen no problems with resistant ryegrass,” he said. “But for those who have seen resistance, it seems to be getting worse.”
Best control option is what he calls the “two-step program.” That starts with a 6-ounce per acre application of Axiom as soon as wheat is up to a stand. That’s followed by a 16.4-ounce application of Axial XL around the first of January, before three tillers.
Swart said the Axiom goes down early, before ryegrass emerges or when the plants are very small. The product has both burn-down and pre-emergence activity; that’s why farmers should wait until wheat is up before applying.
Swart said several experimental products also show some promise for controlling resistant ryegrass. “Nothing shows 100 percent control but several are active,” he said. “The best answer will be cultural. More rotation, staying out of wheat for more than a year, will be important.”
In no-till production, waiting for ryegrass to emerge and then spraying Roundup before seeding wheat also may be effective. “We would hope to get most of the ryegrass up and sprayed before the wheat comes up,” he said.
Swart said the problem has not gotten out of hand yet but urges caution. “If we can’t get a handle on it we could face a situation similar to resistant pigweed in the South. We would not be able to grow wheat on the same field year after year.”
Rotation, he said, makes good sense, anyway. Corn, soybeans, and milo may be good options. “But some of our growers planting soybeans are still having issues with resistant ryegrass.”
Farmer Eric Akins says he doesn’t have a real problem with resistant ryegrass because of rotation. “We rotate every year to stay ahead of it,” he said. He said he has not seen ryegrass resistant to Roundup. “But we may have to bump up the rate a little.”