LAKEPORT >> Aerial mosquito spraying planned for today over portions of Clear Lake has been rescheduled for Thursday morning after a morning sprinkle dampened the target area.
The biodegradable larvicide granules perform more reliably when vegetation around the lake is dry, as they break down rapidly. Lake County Vector Control District needs the product to sink into shallow water, as studies of early season mosquito larvae appear ominous.
The District’s winter mosquito surveillance program has detected large numbers of larvae in the marshlands along the perimeter of the lake that become flooded as the lake rises in winter. These mosquito larvae are an early-season floodwater species (Aedes increpitus) that hatch from eggs laid in the mud in previous years as the lake receded. When winter rains flooded the eggs, the larvae hatched and began developing in the still, shallow water. As temperatures and day length increase in early spring, the Ae. increpitus mosquito larvae will pupate and then emerge as biting adults.
The last time Vector Control conducted aerial larvicide spraying was 2011. Five years of eggs are now hatching.
“It looks like it will be good for mosquitoes — and busy for us,” said Vector Control director Jamesina Scott of the spring mosquito season.
These mosquitoes are the aggressive biters experienced every spring by people living and recreating near this area. In an effort to reduce the number of biting adult emerging this spring, Vector Control will be making an aerial treatment of the marshlands adjacent to the lake between the Clear Lake State Park and Lakeport. Parts of Anderson Marsh State Park, and a small section east of the Clearlake Keys are under consideration depending upon data collected Tuesday.
The product applied will be VectoBac GS, a biological larvicide used to control mosquito larvae in aquatic habitats. VectoBac is manufactured by Valent BioSciences. VectoBac is based on the naturally occurring soil bacterium, Bacillus thuringiensis israelensis (Bti). This highly effective and economical microbial insecticide is registered with the Environmental Protection Agency for the control of larval mosquitoes in nearly all aquatic habitats.
According to Scott, the product does not affect plants, animals, or beneficial insects that live in or drink the water.
Bti is highly selective for the control of mosquito larvae in water — and Vector Control’s primary concern with the early hatch is killing larvae.
“We’re trying to prevent adult mosquitoes,” she said. “They’re a little harder to get. This controls mosquitoes in the water.”
The formulation is a biodegradable solid corncob granule, similar to large sand particles, which are coated with the Bti, which breaks down rapidly in nature so there is no persistence of the active ingredient. The use of a solid formulation reduces the drift onto adjacent property. The larvicide label and the Safety Data Sheet (SDS) are available from the Lake County Vector Control District’s website http://www.lcvcd.org/ or may be requested by calling (707) 263-4770.
The application will be made by a yellow, bi-winged crop duster flying at a low altitude over these marshy areas. Some of the marshy areas are near homes, and people may experience a brief noise nuisance from the plane.
Vector Control’s treatment is expected to begin at 10 a.m. tomorrow.
