CALIFORNIA
Field Crops A SPECIAL GROWERS’ REPORT OF AG ALERT ®
Weedy rice, which is the same species as cultivated rice, competes with commercial rice crops in fields and reduces yields. It remains a top weed concern for rice growers.
New weed culprits emerge, challenging rice farmers By Vicky Boyd
The discovery marked the first time White Water Fire has been found in California and likely the United States, Brim-DeForest said. Native to Africa and China, the newcomer resembles redstem weeds but has a much larger diameter stem and is not related. Little else is known about White Water Fire, but UCCE weed science specialist Kassim Al-Khatib is working to develop a management program using currently registered rice herbicides. Winged primrose willow, which is native to the Southeast, was first found in waterways adjacent to rice fields in Butte County in 2011. So far, the new primrose appears to be con- fined to only one county, although Brim-DeForest said it could potentially spread through waterways and on equipment. The newcomer’s flower has four petals and differs from the common California waterprimrose, which has five. Winged primrose willow also is much taller than its common counterpart. The newcomer gets its name from wings found on its stems, which are noticeable and easy to feel. In addition to seeds, winged primrose willow reproduces through stem parts that can float in irrigation ditches or roots. If growers find the weed, Brim-DeForest recommends pulling it and putting it in a garbage bag for disposal. Chopping the weed or pulling it and leaving it on a ditch bank could potentially spread it.
Bergia capensis, a weed known as “White Water Fire,” has joined a growing list of non-na- tive invaders popping up in the state’s rice fields. Other relatively new invasive threats in- clude winged primrose willow, coast cockspur, or Walter’s barnyard grass, and weedy rice. Should pest control advisors or growers find a weed they’re unsure of or one that isn’t easily controlled with an established herbicide program, University of California Cooperative Extension farm advisors recommend contacting their office for help. “I think people get nervous about reporting, and I can understand why. But if you report it to us, we can help you manage it,” said Whitney Brim-DeForest, a UCCE farm advisor for Sutter and Butte counties. Peter Rystrom, who farms with his father in Butte County, said they continue to watch for the newcomers but haven’t yet found any. They try to keep their fields as weed-free as possible so if something unusual does pop up, it’s apparent. “If it’s a weedy mess, you’re not going to be able to look out and see a new type of barn- yard grass,” he said. “We work really hard on our operation to keep our fields as clean as possible, so when some new type of weed appears, it’s clearly visible and we can see it and identify it.” Brim-DeForest said she planned to conduct additional research into White Water Fire, which was discovered by a Butte County agricultural commissioner’s office inspector in 2023. The weed was found in only three checks of one rice field, and subsequent surveys of nearby fields did not turn up additional infestations.
See WEEDS, Page 15
14 Ag Alert February 7, 2024
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