Thiobencarb exceeded the 1.5 µg/L (parts per million) performance goal to a reading of 2.3 µg/L at the Colusa Basin Drain 5 (CBD5) site off Highway 20. A monitoring site receiving drainage from Colusa and Glenn Counties. This particular exceedance was at the second monitoring event on May 14.
We realize the current weather conditions add to the challenge of maintaining a water hold while establishing a rice stand. Most thiobencarb applications have not been on the field long enough (19-days) to qualify for an emergency release.
Thiobencarb treated fields can be released at 6-days if water is retained on site, or to drains the grower controls. The county agricultural commissioner must evaluate the conditions if a closed or recirculating type system does not exist. If possible, it is best to move the water to a location that does not flow to a main drain.
Some counties are working with rice growers to evaluate options. The Rice Pesticide Water Management Requirements Summary from the Department of Pesticide Regulation might provide thoughts on decisions to release.