A larvicide is a type of insecticide used to control mosquitoes indoors and outdoors around your home. They work by killing mosquito larvae before they can grow into adults. Some formulations are activated when ingested by the mosquitoes, and some formulations work when they come into contact with the larvae.  When used according to product label instructions, larvicides do not harm people, pets, or the environment.

During an outbreak, local government departments and mosquito control districts take the lead for large-scale mosquito control activities. One activity is to apply larvicides. Licensed mosquito control professionals apply Environmental Protection Agency (EPA)-registered larvicides using backpack sprayers, trucks, or airplanes depending on the size of the area being affected.

Homeowners can use mosquito dunks or bits that contain larvicide and can be applied by hand to small bodies of water in the yard and community.

Forms of Larvicides

Larvicides come in many forms.

  • Liquids – Liquid larvicide products are applied directly to water using backpack sprayers and truck- or aircraft-mounted sprayers.
  • Dunks, tablets, bits, pellets, granules, briquettes – These forms of larvicide are also applied to areas where mosquitoes lay eggs.

Types of Larvicides

EPA-registered larvicides have been studied for the effectiveness and safety when used according to label instructions. Public health officials and mosquito control professionals use three types of larvicides: bacterial larvicides, insect growth regulators, and oils and films.

Bacterial larvicides

The following types of larvicides are made from natural substances.

  • The bacterium Bacillus thuringiensis subspecies israelensis (Bti) is found in the soil and is toxic to mosquito larvae, blackflies, and fungus gnats. Bti has been used for mosquito control for more than 30 years.
  • The bacterium Saccharopolyspora spinosa is found in soil and is toxic to mosquitoes, ants, fruit flies, and other insects. Spinosad is a commercial larvicide derived from this bacterium.
  • The bacterium Lysinibacillus sphaericus [PDF – 4 pages] (also known as Bacillus sphaericus) is found in soil. It works well on some mosquito species but does not work on Aedes aegypti.

Insect growth regulators

These types of larvicides prevent mosquito larvae from completing their immature stage, so they do not make it to the adult stage. Methoprene and pyriproxyfen are examples of insect growth regulators.

Oils and films

Licensed mosquito control professions use mineral oils and films to kill mosquito larvae and pupae. Mineral oils and films, when applied to water, spread in a thin layer over the surface of the water. Mosquito larvae and pupae that breathe at the water’s surface drown. Using mineral oils and films are the only effective methods for killing pupae.

Information on insecticides and health

Related Resources

Mosquito Control: What You Need to Know About Larvicides

Mosquito Control: What You Need to Know About Bti