Larvicide

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A larvicide is a product designed to kill insect larvae, especially mosquito larvae. They work in several ways: some are poisons that kill on contact or after being eaten; others are growth regulators that stop larvae from becoming adults; and more recent methods use natural or biological controls.

Biological larvicides use bacteria such as Bacillus thuringiensis israelensis (Bti) and Bacillus sphaericus. These are usually applied as granules on still or standing water. When mosquito larvae eat the bacteria, toxins destroy their digestive systems and they die. They target mosquitoes and some midges, and are generally safe for people and most other animals when used as directed. They usually last a few weeks in water.

Growth regulators like methoprene prevent larvae from developing beyond the pupal stage. Sold under names such as MetaLarv and Altosid, these products are often time-release and can protect larger water bodies for one to five months. They pose low risk to people and wildlife and don’t readily contaminate groundwater, but they can affect some aquatic life and may be toxic to certain fish and invertebrates.

Temephos (Abate, ProVect) is another type of larvicide, an organophosphate that helps prevent resistance to bacterial products. It breaks down quickly and has relatively low human risk, but can affect non-target aquatic species, so it should be used sparingly and where other larvicides are ineffective.

Other approaches include copper’s larvicidal properties, sound or ultrasound that can disrupt larvae, surface films that suffocate them, and even plants engineered to produce natural larvicides. Neem oil has shown larvicidal activity in tests.

Choosing a larvicide depends on the water body, the target species, and safety considerations. When used properly, larvicides can reduce mosquito numbers with minimal harm to people or the environment.