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Researchers continue to combat growing ventenata threat

The invasive grass species ventenata continues to spread throughout northern Idaho and Eastern Washington. University of Idaho plant science professor Tim Prather says the weed can cut the life and production of a stand of timothy hay in half.
Matthew Weaver

Capital Press

Published on July 23, 2018 12:02PM

Last changed on July 23, 2018 12:46PM

Ventenata is an invasive grass species that causes damage to pasture, rangeland and grass hays, particularly timothy hay. University of Idaho plant science professor Tim Prather hopes to keep the weed from spreading more through northern Idaho and Eastern Washington.

Pamela Pavek/University of Idaho

Ventenata is an invasive grass species that causes damage to pasture, rangeland and grass hays, particularly timothy hay. University of Idaho plant science professor Tim Prather hopes to keep the weed from spreading more through northern Idaho and Eastern Washington.


Venetenata is a strange grass, Tim Prather says.

The University of Idaho plant science professor said he has been “frustrated” by the weed for years.

“It’s shallowly rooted, you only find it in the top 3 inches of soil, it’s mostly stem, there’s not very many leaves, it’s not very tall,” he said. “In terms of being in a grass crop, it’s going to be shorter than the crop. And yet, we’re finding that it’s able to take over in long-lived grasses. ... We know there’s no way this small plant would out compete a larger perennial grass.”

However, it’s possible ventenata is a carrier for one or more fungi that cause diseases in other grasses, he said.

Prather said the number of acres ventenata is infesting continues to grow. It occurs throughout northern Idaho and Eastern Washington, and beyond.

It’s a problem in pasture, rangeland and grass hays, particularly timothy hay. It can cut the life and production of a timothy hay stand in half, and hay with ventenata cannot be exported.

“You’re left with a low-quality, domestic hay which might be $50 to $60 per ton, and you’re only getting half the production you should, instead of double the production $250 to $260 per ton,” Prather said.

Ventenata costs $22 million each year in forage damage, he estimated.

Cattle don’t like to eat hay with ventenata, but will eat pelletized hay that contains ventenata, he said.

UI has looked for herbicides effective in removing a grass from a grass, Prather said.

“There are more limited options,” Prather said. “We want to keep the crop as competitive and healthy as possible, so it’s not susceptible to injury by the herbicide.”

UI is looking at other management options, including proper fertilization and soil nutrients, raising the cutter-bar height for timothy hay to 4 inches to help stem development and not grazing in the fall.

Ventenata is not yet listed as a noxious weed. Commodity groups may petition the Idaho Department of Agriculture to get it listed, Prather said.

Tools are available for pasture and rangeland. Prather believes progress is being made, but the weed continues to spread.

He recommends farmers keep an eye on county roads and corridors, places where ventenata likes to move in, for early detection and prevention.

“It has not reached everywhere it could in Idaho,” he said. “It would be nice to stop it from continuing to expand and try to limit its distribution.”

Prather held a ventenata field day July 18 near Albion, Wash., and Moscow, Idaho, providing information on effective herbicides and avoiding further problems for grazing. Washington State University Extension held a field day July 19 in Anatone.



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