Thiobencarb exceedances over the 1.5 µg/L (parts per million) performance goal with a reading of 2.3 µg/L at the Colusa Basin Drain 5 (CBD5) site off Highway 20 and 2.7 µg/L at the Colusa Basin Drain 1 (CBD1) location outside Knights Landing. There also was a detectable reading at the Sacramento Slough site. These exceedances were from the third monitoring event on May 21.
There is no tolerance for exceedances because they place additional scruntity on the future availability of thiobencarb. We understand the additional water in the system adds to the challenges of maintaining water holds and herbicide effectiveness leading to additional applications.
Please continue to communicate with Farm Advisors and the university experts on options if you are considering an herbicide with long water holds such as thiobencarb. Even without rain, the snowpack will begin to melt, leaving us with excessive water throughout the season.