Weeds Continued from Page 14
Previous research found a number of registered products controlled winged primrose willow, including water-ac- tive herbicides Bolero Ultramax, Cerano or Granite GR applied early in the sea- son. Follow-up foliar herbicides include Sandea or Londax applied early. In ad- dition, Grandstand or a Grandstand- propanil tank mix may be applied late. Because the weed tends to grow in waterways and not in rice fields, Brim- DeForest cautioned that some herbicides are not labeled for that use. A purple-awned grassy weed that had been plaguing some rice growers since at least 2017 has finally been identified as coast cockspur, or Walter’s barnyard grass. Native to Eastern U.S. marshes, ditches and shorelines, coast cockspur plants are ro- bust, have large stems and can reach 6 feet tall if not controlled. The identifying trait is the purple awns or hair-like structures projecting from the seed heads. Coast cockspur belongs to the Echinochloa genus, which also includes barnyard grass and early and late watergrass. “Echinochloa species cause huge losses in California rice systems, sometimes up to 100%,” Brim-DeForest said. “It’s the most competitive weed complex in rice.” As part of a larger project that screened for herbicide resistance in Echinochloa
A reddish weed found in Butte County in September was identified as Bergia capensis, or “White Water Fire,” a noxious weed native to Africa and China. It is the first recorded finding of the plant in California.
Because weedy rice is the same species as cultivated varieties, any herbicide that controls weedy rice also impacts the main crop. Currently, only the organic herbicide Suppress is labeled for spot spraying small patches of weedy rice, but the field must first be drained. Growers typically don’t like to remove the flood for fear of spurring new weed flushes. Greenhouse and field trials Brim- DeForest led on the UC Davis campus also have found that two years of fallowing with no deep tillage reduced weedy rice popu- lations to the point where the field could probably be returned to commercial rice. (Vicky Boyd is a reporter in Modesto. She may be contacted at vlboyd@att.net.)
species, researchers looked at potential herbicides to manage coast cockspur. “Granular herbicides did not work for us across the board,” Brim-DeForest said. “With the foliar herbicides, it was a little bit better.” This may be because 80% of cockspur samples were resistant to four different modes of action or chemical classes. Brim-DeForest said she is seeking rice grower-cooperators for field trials this season to look at potential tank mixes to manage herbicide-resistant Echinochloa species, including the purple-awned one. On the good news front, she said no additional weedy rice finds have been re- ported since 2020. That year, farm advisors
conducted a comprehensive basin-by-ba- sin survey on about 11,000 acres that a field-level survey had previously identified as infested. Across the rice-growing region, Sutter County had the highest number of infested acres, while Yolo County did not have any in- festations. Altogether, weedy rice was found on 2,237 acres. Brim-DeForest said she hopes to conduct a similar survey in 2025. Although weedy rice is the same species as cultivated rice, it has evolved or cross- bred to have undesirable traits like red or black pericarps or kernel exteriors. Millers don’t like weedy rice because if they run it through a mill, the discoloration can trans- fer onto white kernels.
YOUR VOTE COUNTS California Rice Industry
Please cast your ballot and have your voice heard!
IN EARLY FEBRUARY, all rice growers and handlers will receive information from the California Department of Food and Agriculture (CDFA) regarding the upcoming continuation referendum for the California Rice Commission. Every five years, a vote of all industry members is required to determine if the industry wishes to continue operations of the Commission. If you do not receive a ballot, please contact CDFA’s Ben Kardokus directly at (916) 749-5473. If you have any questions, please contact the CRC office at (916) 387-2264 .
February 7, 2024 Ag Alert 15
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