rice field

Monitoring for New Problematic Weed Species in Rice

Brian German Field & Row Crops, Industry

California rice growers will need to be on the lookout for two new problematic weed species this year.  One of the species is called rough barnyardgrass (Echinochloa muricata) and the other is known as coast cockspur grass (Echinochloa walteri).  The discovery of the weeds came after two growers having difficulty controlling weeds reached out to University of California researchers for assistance with identification.Problematic Weed Species

“I took it to the Herbarium and they confirmed that both of the samples I took down there were Echinochloa muricata, which is related to the watergrass and barnyard grass species that we have here,” said Whitney Brim-DeForest, UC Rice Farm Advisor for Sutter, Yuba, Placer and Sacramento Counties.  “It’s a native species, it hasn’t been found in rice fields before, so that’s what makes it new.”

The infestations of the problematic weed species were widely dispersed throughout both of the rice fields, meaning that the weeds had most likely been there for a number of years.  There is some concern that traditional herbicides might not be an effective means for management of the two species.  “I couldn’t say for sure, but at least in those two fields it appears to have some tolerance to the rice herbicide and I don’t know if that’s from resistance or if that’s just sort of a natural tolerance to the herbicide,” Brim-DeForest said.

There will be ongoing research being conducted to hopefully identify a genetic marker that can be used for more efficient identification.  “Then I can go and look at the different plants and see if I can come up with a set of characteristics that people could visually identify and distinguish between the two,” said Brim-DeForest.

Rough barnyardgrass and coast cockspur grass look very similar to barnyardgrass, which is common among California rice fields.  Growers and pest control advisors who are having significant challenges with weed management and suspect they may have either species in their fields are encouraged to contact their local UC Rice Advisor.


Listen to Brim-DeForest’s interview below.


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Brian German

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Ag News Director, AgNet West