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Field trials aim to find special-needs herbicide labels for quinoa

By John O’Connell

University of Idaho

MOSCOW, Idaho – Forthcoming field trials at the University of Idaho’s Aberdeen Research and Extension Center could help provide the first herbicides to local farmers who raise quinoa, a niche crop that’s gaining a foothold in the state’s eastern region.

Quinoa, a pseudo-cereal native to South America, has earned a reputation as a superfood for its health benefits. Prices and demand for the crop have been on the rise.

Eastern Idaho has become the nation’s No. 1 production area for quinoa, which fits well into sugar beet and potato rotations.

Without any herbicides labeled for use in quinoa, however, weeds can overrun fields, giving farmers second thoughts about planting it.

The U.S. Department of Agriculture’s IR-4 Project, which helps specialty crop growers address pest management concerns, has approved about $24,000 for quinoa field trials in 2023.

“It’s a pest problem without a solution,” said Ronda Hirnyck, a UI Extension pesticide specialist who serves as the state’s liaison to the IR-4 Project. “The weeds are terrible.”

Pam Hutchinson, UI Extension potato cropping systems weed scientist, will conduct at least two of the trials in Aberdeen, with the goal of finding effective herbicides and getting special-needs labels approved for local use.  

“I’m always interested in looking at crops that have the potential to be grown with potatoes,” Hutchinson said. “The more crops we can get into a three-year rotation, anything like that helps break the cycle of diseases out there.”

The effort to get special-needs labels approved for quinoa herbicides recently took a major step forward when the U.S. Environmental Protection Agency categorized the previously unclassified crop as a grain in September.

The EPA categorization, which is not based on physiology but rather on how quinoa metabolizes pesticides, eliminates the need for hundreds of thousands of dollars in chemical residue testing otherwise necessary to get pesticide tolerances registered with the U.S. Food and Drug Administration.

The categorization allows regulators to base residue decisions for specific chemicals on data already collected for other grains.

The trials should narrow down the list of potentially effective herbicides while also generating additional data of interest to chemical manufacturers.

“The chemical companies may still want at least a couple of studies,” Hirnyck said. “They register the pesticide, ultimately, and they have to accept that liability.”

Quinoa is a close relative of common lambsquarters, which is among the state’s most prevalent weeds, and chemicals effective at controlling lambsquarters also tend to kill quinoa.

Hutchinson plans to evaluate 10 to 15 herbicides in this spring’s trials. During small-scale quinoa herbicide trials Hutchinson previously conducted in Aberdeen, Devrinol, a pre-emergence herbicide labeled for turf grass and certain vegetables, nuts and small fruits, showed promise at eliminating lambsquarters without harming quinoa plants.

The herbicide Dual Magnum was another good candidate. Both chemicals will be included in Hutchinson’s forthcoming trials.

UI Extension has also sought to help growers control weeds in quinoa without chemicals. Xi Liang, UI Extension specialist in cropping systems agronomy, evaluated intercropping with quinoa and varying row spacing from 2018 through 2021, measuring the effects of each scenario on weed density.  

The buyer for the region’s quinoa is Idaho Falls-based Teton Mills, which is the largest quinoa mill in the U.S.

It’s owners, Pingree-based Wada Farms and Driggs seed potato farmers Wyatt and Nathan Penfold, collaborate with a similar-sized quinoa mill in Canada.

Teton Mills aims to contract for 3,000 acres of quinoa throughout eastern Idaho during the 2023 season.

Most of the quinoa is sold domestically, and grower returns are between barley and potatoes. The crop thrives on cooler, high-altitude farmland. Plants can become sterile when high temperatures rise above 90 degrees during the flowering stage.

Wyatt Penfold explained the cost of cleaning quinoa is significant due to the high concentration of weed seeds that must be removed.

“Our plant isn’t like any other plant out there that does any other grains. There’s a whole lot of specialized equipment,” he said.

The Penfolds have done small-scale quinoa trials on their farm for 15 years, testing agronomic practices and potential herbicides and sharing the information with Hutchinson.

Without herbicides available, Wyatt Penfold believes the best approach to raising quinoa is simply to plant it in fields without many weed seeds.

“As of right now we just try to plant it in our cleanest ground we have,” Penfold said. “We follow potatoes or sugar beets.”