What is Bacillus thuringiensis israelensis (Bti) used for in mosquito control?

• A. Bti is a bacterial larvicide producing toxins in the larval gut; environmentally specific with low non-target toxicity; used in standing water.
• B. Bti is an adult mosquito repellent.
• C. Bti increases mosquito reproduction.
• D. Bti is a fertilizer for aquatic plants.

Answer: (A)

Bti is used as a biological larvicide to target mosquito larvae in standing water. It’s a bacterium that produces protein toxins in the gut of larvae; when mosquito larvae ingest these toxins, they disrupt the larval gut lining and cause death. The toxins are activated by the alkaline conditions in the larval gut, and the effects are highly specific to mosquito (and some related fly) larvae, giving environmental safety with low impact on non-target organisms.

This is why it’s applied to standing water—places where mosquito larvae develop, such as ponds, containers, tires, and marshy areas. It won’t kill adult mosquitoes, so it’s not an adult repellent. It’s also not used as a fertilizer; its purpose is to reduce the larval population before they become flying adults.