Weather, resistance make year ‘extremely bad’ for ryegrass

Managing Editor

PAINTER, Va. (June 14, 2016) — Herbicide-resistant Italian ryegrass has been a challenge for a few years in Virginia and other parts of the Mid-Atlantic. On Virginia’s Eastern Shore, weather circumstances have compounded the issue this year in wheat fields.
Resistance issues combined with a warm December that led to more than the usual growth in winter and an early spring that brought on another flush of growth in the fields, Virginia Tech Extension weed specialist Charlie Cahoon said during last week’s field day at the Eastern Shore Agricultural Research and Education Center.
“It just seemed to be a perfect year for rye grass,” Cahoon said. “We are in a mess with it.”
“It’s extremely bad,” said Steve Sturgis, an Eastville, Va., farmer and Northampton County Farm Bureau president reached by phone last week. “It wasn’t there when it was time to spray and then it just got away from us.”
Controlling Italian ryegrass is a big part of Cahoon’s work. In pre-plant applications, Cahoon is looking at flumioxazin-based herbicdes Valor SX and Fierce. He is also working withZidua or Anthem Flex plusAxial XL in delayed-preemergence or post-emergence applications.
Another trial looks at using residual herbicides in a turbo till system to control the weed.
“We’re thinking that the turbo tilling stimulated the ryegrass to all come up at once. Coupling the tillage with a residual herbicide applied delayed-preemergence can give us great control of the initial flush of ryegrass.” Cahoon said.
Cahoon also urged growers to consider adjusting crop rotations as an option for attacking ryegrass. Working a corn crop into land that’s been repeatedly planted to small grains and then soybeans is one option, though Cahoon acknowledged many of the problem fields are not good candidates for growing corn. Shifting from double crop to full season soybeans with a fall fallow period is another option to make progress on controlling ryegrass.
However, the growers have to do some form of ryegrass control in the fall or early spring to deplete the ryegrass population and ensure no seed production, he said.
“Rotation is one of the big problems,” Cahoon said. “We’ve got to do better in our rotations. I know it’s hard on the Shore with the coarse-textured soils and lack of irrigation.”
Another factor at play is the timing and frequency of road maintenance crews mowing along highways and road rights of way, Cahoon said.
“If they could get out a little bit earlier that would really help us, too,” Cahoon said.
Sturgis said the weed growth along roads is frustrating and the issue has come up within Farm Bureau policy discussions. He also sympathized with the limitations on roads crews.
“They just don’t have the budget,” Sturgis said.
Heavier tillage can be another option growers can consider, though Cahoon said farmers are reluctant to turn away from no-till systems and its agronomic benefits.
“No-till has been great for soil health,” he said. “If you can’t get it with any other herbicide, then we need to start looking at tillage.”
To get a better handle on herbicide-resistant Italian ryegrass in Virginia, the Virginia Tech weed team plans to screen ryegrass from across the state for herbicide resistance, Cahoon added. The first year of the project will focus on the I-95 corridor and areas east this fall but growers statewide can submit samples.