UC farm advisers ID new weedy rice biotype in a field

type 6 weedy rice
Type 6 is a new biotype of weedy rice
found in California. Five other bio-
types had previously been identified
Photo courtesy UC Cooperative

This season, University of California Cooperative Extension rice farm advisers were contacted by several growers and pest control advisers to inspect plants suspected to be weedy rice.

When the identification was difficult, farm advisers grew them in the greenhouse to determine if they were weedy or not. Of these, only five turned out to be weedy. The infestations in these fields ranged from a few patches to just one plant.

Unfortunately, one of the five positive samples turned out to be a new type of weedy rice. This new type, which they are calling type 6, has reddish awns early after heading and black hulls at maturity. It is distinguishable from type 4 (which also has black hulls) by the height of the plants (type 6 is tall, type 4 is not).

Growers managing infested fields should keep working to reduce infestations. In some infested fields, the farm advisers were not able to find any weedy plants this year. This doesn’t mean the fields are free of weedy rice, because seeds can survive in the soil for several years. However, it indicates that infestations are being reduced. This is very good news.

New seed regulations come into effect in 2019. All growers should plant certified seed or seed that has been through a quality assurance program. Research and experience shows that the use of certified seed is the best way to prevent the introduction of weedy rice into new fields and stop the spread in infested areas.

Next year, the farm advisers will continue to work with growers and PCAs to identify and reduce the spread of weedy rice in California.

For more information on weedy rice in California, including photos of each biotype, visit CAweedyrice.com.

The University of California Cooperative Extension rice farm advisers submitted this article.

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