Significant Thiobencarb Concentration Detections in Colusa Basin Drain.

The Rice Pesticide Program (RPP) will enter the 8th week of thiobencarb (i.e., Bolero, Abolish, Willowood Thio) monitoring on June 27. The results of monitoring across the sampling sites have generally yielded positive results with only two samples exceeding the performance goal of 1.5 μg/L to date.

However, one of the samples collected on May 30 at the Colusa Basin Drain site west of Knights Landing (CBD1) was reported with a concentration of 6.4 μg/L. This represents one of the highest detected concentrations the program has reported since the California Rice Commission took over management of the RPP in 2003. This concentration is cause for concern for the City of Sacramento and others who take drinking water from the Sacramento River. While there have been no detections at the municipal intakes on the River to date, exceedances in the agricultural drains could lead to detectable concentrations in intakes which could greatly impact the availability and use of the product for the rice industry in the future.

We continue to communicate with the County Agricultural Commissioner's offices, the Central Valley Water Board and the Department of Pesticide Regulation (and program stakeholders) to ensure they receive regular updates to the monitoring results and understand the support of the industry for use of their regulatory authority, including removing the use of thiobencarb from a grower/applicator permit.

As an industry we have the responsibility for the stewardship of this product. The Rice Commission will continue to fully implement the management practices approved by the Central Valley Water Board to promote compliance with the program requirements, including investigation of the source of exceedances.

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