Larvicides target immature mosquitoes, also known as mosquito larvae. The majority of our chemical control efforts are spent on controlling mosquito larvae. We use a variety of larvicide types including microbial insecticides, insect growth regulators and larvicidal films and oils.
A common microbial larvicide is Bacillus thuringiensis israelensis (Bti). Bti is a bacteria that produces a protein crystal that, when eaten by a mosquito larva, destroys the larvae’s intestinal lining. The chemistry of Bti only affects mosquitoes and other insects in the fly family only if ingested. It has no effect on other organisms. Spinosad is another microbial larvicide that is used in specific situations.
Insect Growth Regulators
Methoprene is an insect growth regulator widely used by mosquito control districts. Methoprene mimics an insect hormone to prevent immature insects from shedding its exoskeleton and emerging into adults. Unable to develop into adults, the mosquitoes die in the pupal stage. Methoprene is used in areas where high concentrations of mosquito larvae are found like storm drains, unmaintained swimming pools and some types of flooded irrigation.
Larvicidal Films and Oils
Larvicidal films are generally used for controlling mosquito pupae. Mosquito pupae live in water but do not feed which makes other larvicides ineffective. Oils and films are usually applied by hand to standing water’s surface. The film reduces the surface tension of the water which makes it difficult for mosquito larvae and pupae to attach to the surface and breathe.
Depending on the location and size of the standing water, mosquito larvicides can be applied by:
- Hand-held equipment
- Single-engine agricultural airplanes (crop dusters)
- Backpack sprayer
- ATV or UTV