Larvicides are used to eliminate immature mosquitoes, also known as mosquito larvae. A large proportion of our microbial and chemical control program is spent on controlling mosquito larvae. We have a variety of materials we are able to use for this purpose; among them are microbial insecticides, insect growth regulators, and larvicidal films and oils.
The product known as Bti (Bacillus thuringiensis israeliensis) can be as effective as chemical insecticides. Bti is a bacteria that, when eaten by mosquito larvae, produces a protein crystal that destroys the larvae’s intestinal lining. It has no effect on other aquatic organisms except midges in the same habitat.
Insect Growth Regulators
Methoprene is an insect growth regulator widely used by mosquito control districts. Methoprene mimics a natural juvenile hormone, and when present in the larval habitat it keeps immature insects from maturing into adults. Unable to develop into adults, the mosquitoes die in the pupal stage. Vector control technicians sometimes use methoprene to reach larval sources that would otherwise be difficult to treat.
Larvicidal Films and Oils
Larvicidal films are applied to the surface of standing water. The film reduces the surface tension of the water, making it difficult for mosquito larvae and pupae to attach to the surface and breathe. A significant advantage of using larvicidal films is that mosquitoes cannot develop a resistance, since control is through a physical mode of action.