Department of Pesticide Regulation

MEANING OF "PREEMERGENT HERBICIDES" IN TITLE 3, CALIFORNIA CODE OF REGULATIONS SECTION 6609 (WELLHEAD PROTECTION)

This letter is to clarify the meaning of the term "preemergent herbicides" as used in Title 3, California Code of Regulations (3CCR) section 6609.

The new ground water protection regulations became effective May 27, 2004. As part of those regulations, 3CCR section 6609 was added to protect wellheads from pesticide contamination. Among other provisions, 3CCR section 6609 prohibits application of preemergent herbicides with 100 feet of unprotected wells. That prohibition was adopted because preemergent herbicides are the primary pesticides that have been found in ground water due to agricultural use.

Preemergent herbicides that have been found in ground water are both mobile and persistent, which are characteristic of pesticides listed in 3CCR section 6800(a) and (b) (the Ground Water Protection List). However, some preemergent herbicides are not listed in 3CCR section 6800(b) because they are either not mobile or not persistent. Thus they are considered to have low potential to move offsite to ground water.

For the purposes of 3CCR section 6609, "preemergent herbicides" means preemergent herbicides that are listed in 3CCR section 6800(a) or (b). Examples of preemergent herbicide active ingredients not listed in 3CCR section 6800 include oxyfluorfen (such as Goal), pendimethalin (such as Pendulum and Prowl), prodiamine (such as Barricide and Endurance), and flumioxazin (such as Chateau and Payload).

If you have any questions, please feel free to call Mr. Mark Pepple, of the Environmental Monitoring Branch at (916) 324-4086.

cc:  Mr. Mark Pepple, Senior Environmental Research Scientist
       Mr. James Shattuck, DPR Agricultural Commissioner Liaison