Prevention and Management
Weedy rice (aka red rice) is a major problem in rice production in many parts of the world, and has been identified on at least 10,000 acres in California, as of 2016. Once weedy rice is established in a field, it is very difficult to eradicate since weedy rice plants cannot be controlled with rice herbicides. Furthermore, weedy rice seeds can survive for a long time in the soil, meaning that eradication measures become more difficult if plants are allowed to produce seed. Yield reductions in the southern US are as high as 60% in weedy rice infested fields. If weedy rice contaminates other rice during drying and storage, extra milling and sorting is required, which increases costs and may cause cracking and reduce milling yields.
Weedy Rice Identification Guidelines
Once all watergrass herbicide applications have been made, inspect surviving watergrass-like plants to rule out weedy rice. Check the collar to see if there is a ligule and auricle.
If ligule and auricle are absent, then the plant is watergrass.
If ligule and auricle are present, then the plant is rice or weedy rice.
If a plant looks suspicious, contact a UCCE Farm Advisor to confirm the identification. If the identification is positive, follow the best management practices developed by UCCE.