Administrative Controls

A greater degree of safety in the use of pesticides can be achieved by implementing rules that restrict who can recommend and use aquatic herbicides, and how and when they can be applied. These management practices include Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) regulations concerning product labeling, and federal and state regulations governing herbicide registration and applicator licensing, and permits. The State Water Resources Control Board, National Pollution Discharge and Elimination System (NPDES) permit applies more regulations concerning water quality monitoring.

  • All pesticide label directions will be followed
  • Applicators will operate under a current and valid 'Operator ID Number' issued by a County Agricultural Commissioner
  • Herbicides will be applied by licensed and registered Qualified Applicators (holders of a current and valid Qualified Applicators License (QAL) with an Aquatic Pest Control category issued by the California Department of Pesticide Regulation) only
  • The commercial applicator shall make a site visit to verify the need for treatment and the suitability of the site for treatment prior to receiving a permit. The information gathered (weed species, growth stage, area) will help the applicator determine the method of control, the appropriate herbicides, and amount of herbicide to employ
  • Immediately prior to treatment, the commercial applicator will examine a series of indicators and modify treatment plans accordingly. These indicators include (but are not limited to) heavy precipitation, recreational activity, boat traffic, Secchi depth, and wind. If this examination indicates a potential for reduced control and/or increased water quality impacts, the treatment will be rescheduled. D.O. and temperature readings will be collected at 1 foot below the surface within the treatment area. D.O. levels below 5 parts per million (ppm) and/or temperatures above 80 degrees Fahrenheit (F) will act as thresholds which may prohibit herbicide applications
  • Chemical applications shall be cumulatively restricted to an area of no more than 30% of any individual parcel or ownership as measured between extensions of the parcel's lot lines and lakeward from the shoreline for 300 feet
  • A 16 foot wide boat lane out to open water can also be maintained

Approved Herbicides

Only those registered herbicides which have minimal spatial and temporal impact on beneficial uses will be considered for use in Clear Lake. Those include:

  • Copper based herbicides
  • Diquat
  • Fluridone
  • Endothall
  • Glyphosate
  • 2,4-D
  • Imazamox, penoxsulam
  • Sodium carbonate peroxyhydrate
  • Imazapyr
  • Triclopyr

Herbicides which at present time will not be considered for use include acrolein.


Even after all prudent and reasonable safety steps have been accomplished, some individuals feel at risk from herbicides. Making public notification of herbicide applications gives those individuals an opportunity to take the steps they feel are in their best interest. Prior to the start of the herbicide application season, the Division notifies all agencies having jurisdiction on the lake, by mail, of the upcoming herbicide use. Property owners and/or herbicide applicators are required to notify neighbors that their use of lake water may be restricted by the herbicide application according to the pesticide label.

A fee is due when completed permit is picked-up by applicant.

The established permit fee is insufficient to cover the entire costs of the Clear Lake Aquatic Weed Management Program. The Board of Supervisors currently is providing supplemental funding to cover the unrecovered costs such as those associated with NPDES monitoring and reporting.

Data Collection

The data collected by the county and the herbicide applicators are intended to support the adaptive Clear Lake Aquatic Plant Management Program (APMP). Analysis of data will produce a basis for comparison of how various program elements meet objectives.

Using Arcview, parcels to be treated are shown on a base photograph. A GIS database is used to manage the APMP. This will allow ongoing mapping and tabulation of the total area managed, according to: time period, region of lake, method, herbicide type, and applicator. The applicator will report D.O., temperature and Secchi depth data with herbicide quantity, area treated per parcel (APN), and weather conditions in the Supplemental Pesticide Use Report. A follow-up evaluation and measurement of D.O. and temperature will be made at an interval (about a week) when the greatest mass of dying vegetation might be expected, according to the herbicide employed.

These reports will be sent to the Invasive Species Program Coordinator, Water Resources, by the 15th of the following month.

In compliance with the NPDES permit requirements, sampling for active ingredients will take place during the time period for seasonal herbicide use at the inflow and outflow of the lake and for 10% of treatments with each chemical before, during and a week after application, in order to confirm herbicide dissipation.

Enforcement / Quality Control

Applicators will be required to carry valid permit(s), including the Lake Bed Map or aerial photo with highlighted permit areas. Before leaving the site, the map must be updated to reflect the actual treatment area. Failure to comply may result in fines and the revoking of all outstanding permits.

Failure to truthfully and adequately complete Supplemental Pesticide Use Reports could result in fines and the revoking of all outstanding permits.