Larvicide sprayed over waters


An inter-county health department yesterday launched an aerial effort to prevent the spread of what it said are “highly aggressive” mosquito populations in Marin and Sonoma Counties. The two-day effort by the Marin-Sonoma Mosquito and Vector Control District, which ends today, involves 800 acres over which a helicopter will dump larvicide—an Environmental Protection Agency-certified  form of bacteria—to halt the growth of mosquito populations. Treatment sites are mainly in rural areas, including McInnis Park in San Rafael and Deer Island Basin in Novato. “If left untreated, the department said in a news release, “these mosquitoes could cause severe discomfort to surrounding neighborhoods.” Such precautionary efforts are routine, a spokeswoman for the department said, but the pace at which mosquito larvae develop has increased in recent years.