What You Need to Know About Bti

Mosquito control truck used for spraying larvicides, like Bti.

Mosquito control truck used for spraying larvicides, like Bti.

During a mosquito-borne disease outbreak, local government departments and mosquito control districts take the lead for large-scale mosquito control activities. One activity is to use a toxin produced by bacteria Bacillus thuringiensis subspecies israelensis (Bti). Bti kills mosquito larvae before they can complete their life cycle. Bti does not control biting adult mosquitoes.

Bti occurs naturally in soil and has been safely used in mosquito control for more than 30 years.

How Bti works

Bti kills mosquito, black fly, and fungus gnat larvae when they eat it.

  • Killing larvae that hatch from eggs reduces mosquito populations.
  • Reducing mosquito populations reduces the risk of people getting infected with West Nile, chikungunya, dengue, St. Louis encephalitis, or Zika viruses.

How Bti is used

Bti dunk used to kill mosquito larvae.

Bti dunk used to kill mosquito larvae.

  • Bti comes in many forms, including dunks, tablets, briquettes, pellets, granules, or liquid.
  • Bti can be added to standing water and to containers that cannot be emptied out, covered, or turned over every week, such as rain barrels, fountains, ornamental ponds, and pools that are not in use.
  • Larvicides like Bti may be applied using trucks, airplanes, handheld sprayers, or by tossing by hand.

Bti is not harmful to people, honeybees, animals, and the environment when used as directed

  • Bti is not toxic to people. It has not been shown to make people sick.
  • Bti will not harm people, pets and other animals, aquatic life, or other insects, including honeybees.
  • Bti is an insecticide registered by the Environmental Protection Agency (EPA).
    • EPA-registered insecticides have been studied for their effectiveness and safety when used according to label instructions.
    • Existing residential and area-wide uses, like aerial or truck spraying, have been evaluated and found to be safe.
    • Bti is EPA-registered for use in residential, commercial, and agricultural settings. Organic farming operations use Bti.
  • When used as directed, Bti can be applied safely to standing water where mosquitoes lay eggs without causing harm to food crops or water supplies.
  • Multiple Bti products are available for use. Always follow label instructions to ensure that the product is being used correctly.
  • Bti is most effective when used as part of an integrated mosquito management plan for reducing the number of mosquitoes in an area.
Related Resources

Mosquito Control: What You Need to Know About Bti