Glyphosate resistant pigweed currently may be attracting more attention, but to an increasing number of Southwest wheat growers, herbicide resistant ryegrass poses an equally disturbing dilemma.

For several years, farmers, industry representatives and Texas AgriLife Extension specialists have noted that once-effective herbicides have failed to control some ryegrass in wheat stands.

A group of interested parties met at plots near Fairlie, Texas, to review control options for this increasingly worrisome problem.

Jim Swart, Texas AgriLife Extension integrated pest management specialist, has been looking at options for several years, especially after noticing that a control standard, Axial XL, was no longer effective in controlling some ryegrass. He said another once-effective herbicide, Hoelon, had been phased out of recommendations several years ago when ryegrass displayed resistance.

Last year Swart estimated about 10 percent of the wheat in northeast Texas showed resistant ryegrass infestations. “I think that’s closer to 20 percent this year,” he said.

Tony Driver, a tech representative for Syngenta, manufacturer of Axial XL, said the problem seems fairly localized “but must be taken seriously. This can be a serious problem if we don’t address it.”

The best solution so far is what Swart calls a “two-step program,” a resistant ryegrass management system that keeps Axial XL in play. The program calls for application of Axiom, a Bayer CropScience herbicide, at 6 ounces per acre when you can “row your wheat. We don’t want to apply until wheat is up to stand, as Axiom has some preemergence activity,” Swart said.  Following that, Axial XL is applied at 16.4 ounces per acre at the two-leaf stage of ryegrass, usually in early to mid January. “We add a half-ounce of Amber with Axial XL to control broadleaf weeds,” he said.

That combination has taken out the resistant ryegrass. “And it keeps Axial XL available,” Swart said. “Axial XL has been doing a good job and is still doing a good job in many places.” He said using Axial XL in combination with Axiom allows farmers to keep a good herbicide available when ryegrass becomes resistant. “We really have nothing to replace Axial XL,” Swart said.

He’s looked at Axiom for about 12 years but until recently could find no real fit because “Axial XL was doing such a good job. Now, we can apply Axiom early and come back with Axial XL and take out resistant ryegrass.”

Swart said a commercial field near the test plots failed last year and was overrun with resistant ryegrass. “They used the two-step program this year and will make a good wheat crop. This program is going to buy us a lot of time.”

Gary Schwarzlose, Bayer CropScience tech service representative, said Axiom also has some broadleaf activity, mostly on mustards and henbit.

Swart and other industry representatives cautioned farmers to be alert to potential resistant ryegrass infestations and to watch for “slippage” of current herbicide programs.

“Pay attention when you combine wheat,” Swart said. “If you see ryegrass at harvest following anAxial XL application, it may be resistant. And you can scatter seed all over the field with the combine.”

Russell Sutton, Texas AgriLife research agronomist, said ryegrass seed spreads easily. “We can spread it with a combine, other farm equipment” or through natural means — wind, birds, etc.