UC Extension receives weedy rice research funding

weedy rice
Not all of the five cultivars of weedy rice are taller than commercial varieties. At least one actually is shorter—photo by Timothy Blank, California Crop Improvement Association

As this season starts, growers and pest control advisers should continue to be mindful of weedy rice. As mentioned in last year’s communications, in 2017 University of California Cooperative Extension received 22 new samples. Fortunately, the infested acreage did not increase much, and the Sacramento Valley still has about 10,000 acres.

For 2018, UCCE has received funds from the California Rice Research Board and the University of California to conduct weedy rice research, according to a UC rice grower newsletter

In fact, rice farm adviser Whitney Brim-DeForest was awarded the $1 million UC Cooperative Extension Presidential Chair for California Grown Rice. Half of the funding comes from the research board and the other half from UC.

The California Rice Commission is continuing to support UCCE’s outreach activities related to weedy rice.

The chair is for five years, after which it will be reviewed. Brim-DeForest is part of a team of UC scientists that includes UCCE advisors Luis Espino and Michelle Lindfelder-Miles, and UCCE specialists Bruce Lindquist and Kassim Al-Khatib.

The research conducted on California weedy rice last year has produced information that can be used to better manage this weed.

For example, soil samples of some infested fields showed that the seedbank is large, indicating that the weed has been in these fields for some time.

UC farm advisors will continue to track those fields this year. Also, they learned that there are differences among weedy rice types in their dormancy. Three out of the five types we have in California have high dormancy, making them more challenging to eliminate from the field than the other two types, which have low dormancy.

They also tested several herbicides for spot-treating infestations, and work to obtain a registration is underway. For more information, Whitney’s presentation from this year’s winter meetings is available here.

“We don’t know where weedy rice came from,” Brim-DeForest said in a UC news release. “It’s a weed in every major rice growing area around the world. We were among the last areas to see it.”

One of the challenges is weedy rice is the same genus and species as commercial rice: Oryza sativa. So most herbicides that will control weedy rice will damage or kill commercial rice.

In the UC Davis experiment, the scientists plan to demonstrate two potential weedy rice management strategies: rotate the rice crop with sorghum and create a “stale seed bed,” in which the field is irrigated and plants allowed to germinate, and then killed with an herbicide before the desired rice is planted.

“We want to demonstrate this in the field,” Brim-DeForest says. “In theory, it works. We want to show growers how long it will take to get weedy rice out of their fields.”

This season, UCCE plans to have field days to help growers and PCAs with weedy rice identification. They also encourage growers and PCAs to continue to call UCCE rice advisers if they suspect weedy rice infestations.

For more information on California weedy rice, including images of the five different biotypes, visit http://www.caweedyrice.com. If you have any questions, don’t hesitate to contact the UCCE rice advisers.

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