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Researchers consider ventenata controls

Matthew Weaver

Capital Press

University of Idaho researchers are working to find methods to control ventenata, a grassy weed that's spreading throughout the Pacific Northwest. The crop damages timothy hay chances in overseas markets and costing roughly $22 million annually. UI professor Tim Prather says seeds can last for several years.

AIRWAY HEIGHTS, Wash. – Northwest researchers are working to find the best ways to manage ventenata, a growing problem in several different areas of production.

UI professor Tim Prather spoke about the grassy weed during the Spokane County Crop Improvement Association annual meeting in Airway Heights, Wash., near Spokane.

Ventenata is impacting timothy hay, pastures and rangeland and Conservation Reserve Program lands.

The weed reduces hay production, shortens stand lives, and, if found, excludes hay farmers from overseas contracts.

The difference can be as high, reducing $258 a ton for overseas contracts to $70 per ton for hay with ventenata, Prather said.

He estimated the total loss due to ventenata in the region is about $22 million per year.

Ventenata occurs throughout the Pacific Northwest and is spreading, recently spotted in Twin Falls County in Idaho for the first time.

It has a shiny appearance whether green or tan, and has seeds appearing similar to a miniature wild oat. There is a brown-purple band at the node near where the leaf comes away from the stem. There is also a long ligule Prather likens to “those annoying tags on the back of your shirt.”

Ventenata is high in silica, and will cause swathers to shudder or stop as they move through the field. The silica deters feeding by large animals and insects, Prather said.

Native to Africa, ventenata emerged as a problem in the Pacific Northwest during the mid 2000s. It has a low root depth, so it would not appear to be competitive, but has edged out weeds like cheatgrass or medusahead in some areas in northern Idaho and eastern Oregon.

Researchers are considering treatments for high ventenata and low ventenata. Prather said phosphorus and potassium are lower in fields where there is high ventenata.

Herbicide efficiency improves by roughly 10 percent after ventenata plants emerge in the fall, Prather said.

Some herbicides act very slowly, with results occasionally occurring in late spring after fall applications, he said.

Burning is more successful in low ventenata where there is more plant material, Prather said.

As litter on a field builds, the better the weed survives, he said. Prather and other researchers are examining tactics to help on CRP lands.

Researchers have found most ventenata seeds germinated right away, but seeds can survive for longer, roughly less than five years.

“If you’re looking at pulling a hay field out and cropping it to something else for a while, you’ve got to do a very good job of control for a number of years in order to prevent this grass from coming back,” Prather said.



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