Keeping weeds in check

Weed management in Treasure Valley means finding strategies to thwart weeds without injuring crops or the environment. Such strategies are complex; just ask OSU weed scientist Joel Felix when he’s knee-deep in yellow nutsedge.

“An onion field makes a welcoming environment for this weed,” he says, gesturing toward a healthy crop of grassy-looking nutsedge. “The onions are short, with shallow roots, so there’s plenty of space for the weeds to spread out in the sunlight and soak up moisture from the irrigation.”

[caption caption="OSU weed scientist Joel Felix knee-deep in yellow nutsedge. (Photo by Peg Herring.)"][/caption]

Felix fights weeds by first understanding how they grow and why they’re here. Yellow nutsedge, for example, thrives with sunlight and water, the kind of place that’s favored by Treasure Valley’s famous onions and potatoes. It’s part of a big group with more than 140 members, some prized for their golden blossoms or tasty tubers; some despised as persistent weeds. In the irrigated fields of Treasure Valley, it is prolific.

Once established, yellow nutsedge is very hard to control, Felix said. It can sprout new little plants from small tubers called nutlets that can persist buried deep in the soil for up to six years. It can even embed itself and reproduce inside potatoes.

Station researchers have tried lots of management approaches, but they’ve not yet found the silver bullet. They’ve learned that frequently cultivating fields can be effective, but it is impractical in onion fields. Fumigating with a combination of chemicals is also effective, but it can be expensive and hard on the beneficial microbial life of the soil. They are currently testing a combination of herbicides and crop rotation that seems most promising.

Treasure Valley growers look to the Station for new approaches and research-based recommendations for controlling weedy invaders such as yellow nutsedge as well as downy brome, hairy nightshade, and Russian knapweed. Each year the Station hosts the Snake River Weed Management Research Tour, where growers and scientists wade knee-deep into the issues of weed control in Treasure Valley’s treasure trove of crops.