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WFP_Todd_Fitchette_Timothy_Blank_Weedy_Rice.jpg Todd Fitchette
Timothy Blank of the California Crop Improvement Association takes samples of weedy rice from a northern California rice field. Growers are now required by law to use certified seed, or in the case of varieties where seed ownership is unknown -- like Japanese varieties and some colored rice -- stringent quality assurance protocols are employed to ensure growers get clean seed.

Certified seed now required for California rice growers

California rice growers must now plant certified seed. No more saving seed for the following year.

What started 20 years ago as an industry conversation over potential pest and disease challenges culminated with the implementation of a certified seed program now required of all rice growers in California.

The forward-thinking action of the California rice industry that now has a 12-member board that reports to the Secretary of Food and Agriculture is an event, in hindsight, California Rice Commission President Tim Johnson says allowed the industry to require and police a new certified seed requirement under the marketing order governing rice.

“Looking back 20 years this is probably one of the more significant actions we’ve taken as an industry,” Johnson said. “We could not have required that all seed in 2019 be a class of quality assurance or certified seed had it not been for this act.”

Weedy rice

The rediscovery of weedy rice, also known as red rice, in California in 2003 is today why the industry added this layer of protection to preserve the quality and integrity of its medium-grain and specialty rice production.

Since its discovery in a northern California rice field in 2003 the University of California has surveyed 14,000 acres of rice checks that have some level of weedy rice infestation.

“It’s how we count the fields,” said Whitney Brim-DeForest, Cooperative Extension rice advisor for the counties of Sutter, Yuba, Placer, Butte and Sacramento.

For instance, a 40-acre check identified with several weedy rice plants will be counted as 40 acres, even though there may be a small patch of red rice in the field.

What is it?

Weedy rice is the same genus and species as cultivate rice, according to Luis Espino, Cooperative Extension rice advisor in the counties of Yolo, Glenn and Colusa. This creates several challenges related to identification, rice quality at milling, and control. Current herbicides used in rice cannot control it. Hand rogueing is the only effective method to control its spread as seed can lay dormant in the soil for years, Espino said.

There are six identified biotypes of weedy rice in California with two more possible biotypes being studied by experts for inclusion.

Historical records show weedy rice in California was present in 1917. In 1980 a researcher wrote that weedy rice could not be found in California.

In 2003 it was reported in Glenn County. By 2006 six fields in Glenn and Colusa counties had a single biotype of the weed.

“Some of these fields are still dealing with it,” Espino said.

By 2016 five biotypes of the weed had spread to several thousand acres of northern California rice fields.

What makes weedy rice troublesome for growers isn’t just the reduced quality of milled rice; weedy rice shatters easily, meaning it falls from the plant and then becomes seed that aids in its spread. Common cultivation practices can spread this seed across fields.

The weed also competes for fertilizer and space in the field. Studies from the southern U.S. documented yield losses of cultivated rice ranging from 27-45 percent, Espino said.

Certified Rice

California now requires growers to document and prove their use of certified rice seed, according to Charley Mathews, a rice grower near Marysville, Calif. and current chairman of USA Rice.

“We gave everybody a heads up on this a few years ago,” Mathews said.

The 2019 crop year is the first season where certified rice seed is required. Enforcement of this is handled by the California Department of Food and Agriculture.

“Looking back, we were well-positioned when weedy rice popped up to control this as an industry and set these protocols in place,” Johnson added, noting that other rice-producing states have been watching California and may be working to emulate similar programs in those growing regions.

California rice seed is either certified clean by means of documenting the seed source or is subjected to quality assurance protocols in the case of Japanese rice varieties, where U.S. officials cannot certify the original seed source because they don’t own it. For most of the rice planted in California – medium grain varieties developed by California researchers account for over 85 percent of the planted rice in the state – this is not an issue as the origin is documented and traceability is assured through foundation seed sources at the Rice Experiment Station.

Timothy Blank, certified seed program representative with the California Crop Improvement Association (CCIA), said the rice certification and quality assurance process is operated through the non-profit CCIA. The organization is an approved third-party group called for in the marketing order to assure cleanliness of the seed used.

“We’ve had a zero-tolerance for red rice from the beginning,” Blank said.


While weedy rice plant types vary, they are usually taller, lighter green, and more vigorous with more tillers than cultivated rice, Espino said. Nevertheless, it requires verification by university specialists or the CCIA as it can easily be confused with watergrass or sprangletop.

The University of California no longer encourages growers to pull suspected plants and transport them to the Rice Experiment Station for identification. Growers are urged to contact their local rice extension agent for instructions on how to handle identification. UC now has a weedy rice reporter mobile app that can be used to report potential finds. The mobile app can geotag the location, making it easier for researchers to find suspected weedy rice finds.


Aside from using certified seed, growers can employ stale seedbed protocols in the spring and during the growing season. Prior to that, Espino says disking should be avoided post-harvest to prevent the spread of seeds. Burning and flooding during the fall and winter may help, Brim-DeForest says, but she cautions that research does not yet back up this theory.

Hand rogueing remains the most effective means of weed control as herbicide treatments are either ineffective or not labeled.

While the Rice Commission successfully won another year of approval to use Intrepid on the Armyworm, efforts to gain provisional approval for spot treatments of weedy rice were not approved by the California Department of Pesticide Regulation. The California Rice Commission continues to work with DPR and private industry on herbicide technologies that could improve weed control options for California rice growers.

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