By MITCH LIES
SALEM -- Two consecutive rainy springs are being cited as the primary reason for an influx of roughstalk bluegrass in Willamette Valley grass seed.
With the industry's top control option all but eliminated, growers are finding it difficult to keep the weed in control and keep stands viable.
In some cases, growers will be wise to pull out stands earlier than planned, according to Andy Hulting, Oregon State University College of Agricultural Sciences weed control specialist.
"Particularly, some of the tall fescue fields are going to have to come out, because we don't have the tools to manage it in those fields," Hulting said.
Hulting said roughstalk bluegrass has been present for decades in the Willamette Valley and Central Oregon, where it is grown as a turf grass.
The weed typically is a minor problem, Hulting said, but has flourished over the past two years.
"It definitely likes these cold, wet, late springs that we have had the last two years," Hulting said. "It has adapted to these wetter sites in these established fields."
Also, the herbicide Rely is in limited supply right now, Hulting said, and no other good control options are available in grass seed.
Several issues have combined to exacerbate the problem of roughstalk bluegrass, Hulting said, including that the plant can behave like an annual, biennial or perennial plant and deposit up to 30,000 seeds per plant.
"This is going to be a serious issue that we're going to have to deal with over the next several years now that we have this big build-up of the roughstalk population," Hulting said.
"I think it is more of a problem in the south valley but we need to be worrying about it in the north valley, as well," Hulting said.
Changes in crop management practices designed to increase water-holding capacity of soils also, ironically, are leading to an increase in roughstalk bluegrass, Hulting said.
"Typically where we have full-straw loads, no-till systems -- anything we're doing to increase the water-holding capacity of soil -- that is where we are selecting for roughstalk bluegrass," Hulting said.
Hulting said that in established fields with historically heavy weed pressure, growers should consider mid-winter soil-applied herbicides to extend the residual control of herbicides.
But the main control option, he said, is to keep clean fields clean.
"If you've got a clean field, you want to keep it clean, because once that stuff comes up, you cannot control the established plant," Hulting said.
He spoke to grass seed growers Dec. 11 at the Oregon Seed League's annual convention.