We have conducted field surveys of weedy rice in 2020 and 2025. The objectives were to document the location of weedy rice infestations, determine how severe these infestations are, and evaluate the spread of this weed.
In 2020, we inspected 15,748 acres of rice. Of these, 3,412 acres (21% of surveyed acres) had weedy rice. Five years later, in 2025, we re-inspected these fields and inspected a few fields where new infestations had been identified. In 2025 the total area inspected was 16,347 acres. Of those acres, 3,002 acres were determined to be infested with weedy rice (18% of surveyed acres). Comparing surveys, the total acres infested with weedy rice was lower (400 acres) in 2025 than 2020. Additionally, the severity of infestations decreased. In 2025 we found an increase in the acreage infested at low levels but a decrease in the acreage infested at high levels. In 2025, 1,419 acres were infested at level 1 (less than 10 individual plants per basin), compared to 785 acres in 2020. Similarly, acreage at level 2 (more than 10 individual plants per basin) was 963 in 2025 compared to 918 in 2020. On the other hand, acreage with moderate to high infestation severity (5 patches or less to 25% of basin infested) dropped from 1,708 acres in 2020 to 619 acres in 2025. Weedy rice types 1, 2 and 3 accounted for most of the infestations found in 2025. Acreage infested with type 1 decreased from 2,398 acres in 2020 to 936 in 2025. However, acreage of types 2 and 3 increased from 692 to 1,438 and from 292 to 513, respectively. Types 4 and 6 were not found in 2025, while type 5 was found in one 36-acre field.
We would like to thank all of those who allowed us to inspect their ranches and commend the industry on their hard work helping to slow the spread of weedy rice in the rice production areas of California. We will continue to conduct research and outreach to help combat this troublesome pest. Please visit our website for more information on weedy rice (https://caweedyrice.com/).