The legality of a longstanding agreement that keeps pesticides out of West Marin has been challenged mere months before it expires on December 31. 

In August, the Marin/Sonoma Mosquito and Vector Control District received a memorandum from its legal counsel, Janet Coleson, stating that its near decades-long agreement with the West Marin Mosquito Council may illegally prevent the district from conducting pest-control programs effectively, as required under California law. 

At the heart of the matter lies the district’s use of methoprene, an insecticide that some studies have shown to be toxic to fish and that members of the council adamantly oppose. The district considers methoprene to be one of the most effective methods for mosquito abatement and has routinely applied methoprene outside West Marin—773 pounds in briquette and pellet forms and 18 gallons of liquid in 2013, according to the California Department of Pesticide Regulation.

Established in 2007 and renewed with a variety of additions, the original “Working Mosquito Control Agreement” prohibited all but nine of the 36 pesticides that district uses from being applied in West Marin. Of these, the agreement also forced the district to obtain consent from landowners before using one pesticide—Agnique MMF—on their properties.

Both of these provisions, Ms. Coleson’s memorandum states, may make the agreement an illegal delegation of the district’s “police power” to curb pest populations and may grant an improper veto to the council—which the memorandum describes as “an unincorporated association of individuals”—over actions taken by a government agency. The memorandum also noted that the district could potentially expose itself to litigation and damages if it broke the agreement by using non-approved pesticides.

“By restricting or penalizing the future exercise of the District’s power to abate mosquitoes and other vectors, the Agreement could be considered a ‘surrender,’ ‘abnegation,’ ‘divestment,’ ‘abridging,’ or ‘bargaining away’ of the District’s control over a ‘government function,’” the memorandum states. “Such an agreement risks nullification by the courts.” 

Ms. Coleson’s memorandum concludes that, at minimum, a revised agreement should allow the district to terminate the agreement at any time and for any reason. The memorandum also suggests that the district consider splitting its jurisdiction into additional zones to assess proportionate program costs and services, which the district has claimed are higher and more time-consuming in West Marin than elsewhere. The district is currently divided into three zones, one of which encompasses both West Marin and a large portion of Sonoma County.

Members of the council—formerly known as the West Marin Mosquito Control Coordinating Council—met privately at the Dance Palace on Monday to discuss Ms. Coleson’s legal opinion. While the council declined to elaborate on the details of the closed-door discussion, its co-chair, Liza Goldblatt, emailed the Light that “our main interest is to renew the contract with the District and we believe that the legal opinion does provide options to do this.”

The council hopes to discuss the longstanding agreement with a control district subcommittee that coordinates with West Marin before the district’s next meeting. That meeting will likely be held in Point Reyes Station and be open to the public, Ms. Goldblatt said.

During the open session of Monday’s meeting, Vic Amoroso—who represents the Bolinas Community Public Utility District on the council—objected to the potential use of methoprene in West Marin. Bolinas residents, he said, are allowed to dump their septic sewage into its wastewater treatment facility, and methoprene briquettes added to mosquito-infested septic tanks could flow into the nearby Bolinas Lagoon. Septic tanks located in the town’s Gospel Flat area, he added, are also prone to flooding.

“The biggest objection to methoprene is not the organic farming,” said Mr. Amoroso, referring to a provision in the agreement that restricts Agnique MMF from being applied on or immediately near organic farms. “It’s the aquatic life. We have a lot of places of exposure.”

Ms. Goldblatt urged the council to renew its request for the district to consider using the insecticide Merus; its active ingredient, pyrethrum, is sourced from dried flowers. That product would replace Agnique MMF—which is being phased out by the manufacturer—and is endorsed by the Organic Materials Review Institute, an international nonprofit that the council views as the leading voice for pesticide standards. 

Earlier this year, the control district extended the agreement until the end of the year as long as the council would allow 18 insecticides, rather than nine, to be used in West Marin. At the time, the district also called for an independent evaluator from the University of California, Davis, to study the environmental effects of time-released methoprene briquettes in onsite wastewater treatment systems.

But Ms. Goldblatt said that the council decided to not participate in such a study, due largely to Bolinas’s opposition to methoprene.

The district’s general manager, Phil Smith, expects that the issue of whether to introduce methoprene into West Marin will be raised at the Oct. 14 meeting.