Larval Control

Larviciding is the process of controlling mosquitoes when they are in the larval or pupal form. Controlling mosquitoes when they are in the water is an effective approach because the mosquito is isolated, and known breeding sites can be recorded and routinely monitored. For many Districts, including UCVCD, this is the bulk of their operations. This is the best means to fight mosquitoes because they are stopped before they take to the air, before they can spread disease, and pose the lowest possible risk to the environment and non-target species. There are a number of different products available for abatement practices. Often times, one product will be better suited for a particular situation than another product. 

Larvicides We Use:

Bti: Bacillus thuringiensis israelensis (Bti) is a naturally occurring soil bacterium. The bacterium produces proteins in a crystalline form. When the mosquito larvae eats these crystals, the proteins attack their gut wall, paralyzing the larvae. Bti has a highly specific mode of action, and is of minimal environmental concern. Bti is quickly biodegraded and leaves no residue. UCVCD uses Bti in a number of formulations to include granular, briquettes, and liquid. 

B. Sphaericus: Bacillus sphaericus works very similar to Bti. Mosquito larvae of susceptible species ingest a lethal dose of B. sphaericus crystals and spores. Toxins are released in the larval midgut, paralyzing and damaging the digestive system. The larvae undergo tremors, become sluggish and die with 48 hours. Bs is nontoxic to non-target organisms.

Larviciding Oil: Oils and mono-molecular surface films are used to control pupae and late-fourth instar larvae. A small amount of this product will sheet across the surface of water and interfere with their ability to attach to the surface of the water to breathe. These products are used only when an adult emergence will occur without treatment and has little effect on other aquatic insects. 

Methoprene: Methoprene is an insect growth regulator (IGR) that interferes with normal mosquito development. Methoprene is absorbed through the skin of the larvae and disrupts the normal development cycle resulting in the inability to complete metamorphosis. Field inspectors use Methoprene to pre-treat areas that are known to flood and hold water.

Spinosad: Spinosad is a product derived from a naturally occurring soil bacterium and has a unique mode of action different from the other larvicides we use. Mosquito larvae are susceptible to this product by ingestion as well as by contact. The formulations UCVCD uses are classified as a Reduced Risk product by the EPA and are OMRI (Organic Materials Review Institute) Listed, enabling them to be used in and around organic agriculture. Spinosad breaks down quickly and does not bioaccumulate in the environment and has received the Presidential Green Chemistry Challenge Award.