Pyrethroid and Water/Sediment Toxicity Results to Date 

The California Rice Commission collects data on pyrethroids and toxicity in water and sediments at our four main agricultural drain sites in accordance with the Basin Plan Amendment Total Maximum Daily Loads (TMDL) requirements under the Clean Water Act. Pyrethroids (i.e., Warrior, Lambda-cy, Silencer) are used in rice production to manage insects.

On May 30, 2023, water monitoring data results indicated detection of pyrethroid and a statistically significant mortality (toxicity) at the Colusa Basin Drain near Colusa. This same location had similar results in 2021. According to the TMDL, we anticipate that these two results at the same location within a 3-year window will require the implementation of a management plan. In addition, a statistically significant mortality (toxicity) occurred in June 2023 in sediment analysis at Sacramento Slough near Karnak. The corresponding water toxicity test indicated no statistically significant mortality (toxicity). Further testing is being conducted.

For more information, contact the CRC’s Industry Affairs Manager Craig Riddle at criddle@calrice.org or (916) 812-3468.