South S.L.V. Mosquito Abatement

Bacillus thuringiensis subspecies israelensis, commonly referred to as Bti, is a bacterium found naturally in soils. Since 1982, it has been used successfully worldwide as a biological pest control agent to combat mosquitoes and blackflies.

How Does Bti Work?

During the spore-forming stage of its life cycle, the Bti bacterium produces a protein crystal which is toxic only to mosquito and blackfly larvae. These microscopic crystals are ingested by insect larvae when they are feeding. In the alkaline environment of the susceptible insect’s digestive system, the crystals are dissolved and converted into toxic protein molecules that destroy the walls of the insect’s stomach. The insect usually stops feeding within hours and dies within days.

How is Bti Used?

Bti is applied directly to the water where mosquito and blackfly larvae are found. The bacteria are suspended in the water where the larvae will ingest it. None of the products containing Bti should be applied directly to human drinking water.  Bti is also used to control fungus gnat larvae in greenhouse ornamental plants.

Are There Health Concerns Related to the Use of Bti?

Bti poses little threat to human health through either handling products directly or being exposed to them indirectly, e.g., during a provincial or municipal mosquito control program. To activate Bti toxins, alkaline conditions that exist only in certain insects’ digestive systems must be present. The acidic stomachs of humans and animals do not activate Bti toxins. There have been no documented cases involving toxicity or endocrine disruption potential to humans or other mammals over the many years of use in Utah and around the world. Studies have shown that even if Bti spores are ingested or inhaled, they are eliminated without any adverse health effects. All formulations are evaluated according to internationally accepted scientific protocols for their potential to cause skin or eye irritation or sensitization and acute toxic effects. These tests are designed to show if the product has the ability to produce health effects or trigger allergic-type reactions. The fact that Bti is a naturally occurring, widely distributed organism in the environment means that the average person would have multiple exposures to this bacterium throughout their lifetime, even if they never came in contact with a formulated product. Applicator exposure during use in provincial and municipal mosquito and blackfly programs is minimal, since the product is applied directly to the water where the larvae exist. None of the products containing Bti should be applied to treated, finished drinking water. Members of the public are unlikely to experience any symptoms if inadvertently exposed to Bti use, and no special precautions are necessary or required. Individuals who have concerns, however, should take reasonable precautions to avoid exposure during a spray program in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued. They can also reduce exposure by staying indoors with windows and doors shut during the spray period if spraying is taking place in their area, although this is not required by health officials.

What is the Effect of Bti on the Environment?

Bti only becomes toxic in the stomachs of mosquito and blackfly larvae. Because of this, it does not affect other insects, honeybees, fish, birds or mammals. The United States Environmental Protection Agency categorizes the risks posed by Bt strains to non-target organisms as minimal to non-existent. The insecticidal toxin biodegrades quickly in the environment through exposure to sunlight and microorganisms.\

How Can You be Sure That Bti is Not Affecting Health or the Environment?

Different varieties of Bt, including Bti, have been widely used in insect control programs in the U.S. for many years and have demonstrated a remarkable safety record. The weight of scientific evidence indicates that Bti is non-infectious and non-toxic to humans and other mammals and poses little risk at dosage levels permitted in insect control programs. While adverse effects have been observed in individuals of some non-target aquatic insect species, no lasting impact on the populations of these species has been shown from the use of Bti.

South Salt Lake Valley Mosquito Abatement