Researchers from UC Cooperative Extension (UCCE) are looking closely at the watergrass issues in California rice fields to get a better understanding of the problem. Watergrass has historically been a fairly common weed species that growers face, however in recent years the issue has been compounded by a number of factors. Several watergrass species have demonstrated resistance to the materials available and it appears that one or two new species may have emerged.
“In the past few years watergrass is becoming more and more of a problem, whether it’s the ones that we know that we have or these possible new species,” said Whitney Brim-DeForest, UC Rice Farm Advisor serving Sutter, Yuba, Placer, and Sacramento Counties. “It’s just becoming more difficult to control with the herbicides that we have.”
The level of watergrass issues that growers are dealing with is exacerbated by increasing resistance to the materials that are available. Many watergrass varieties are proving resistant to multiple herbicide modes of action. Brim-DeForest noted that the most recent registrations for herbicides have not been exceptionally effective in combatting watergrass in rice fields. “We have some [new materials] coming down the pipeline that we’re hoping maybe will be available in the next two-to-three years that are better watergrass materials and so we’re hoping that will help a little bit,” Brim-DeForest said.
Rice Farming Systems Advisor Luis Espino and Brim-DeForest have both been working to better understand the watergrass issue, through collecting and screening samples from rice fields. UCCE personnel will be out surveying rice fields this fall to get a better grasp on the situation. “Some growers are dealing with [new species] and some are dealing with the known watergrass species that are more resistant to herbicides. So, I would say its sort of a number of things sort of all coming together all at once,” Brim-DeForest noted.