Mosquito larval control
Mosquito larval control
Use of a mosquito larvicide may be beneficial when it is impractical to eliminate a breeding site. Larvicides are insecticides which are used to control immature mosquitoes before they have a chance to develop into biting adults. Trade names of some larvicides are: Mosquito Dunks, Mosquito Quick Kill Granules, and Agnique MMF.
Most larvicides sold to homeowners contain either the active ingredient methoprene or a toxin produced by the soil bacterium Bacillus thuringiensis israelensis (Bti). Methoprene prevents adult emergence by disrupting the development of mosquito larvae. Bti toxin attacks the digestive tract. It is lethal only to mosquito wrigglers and the larvae of some aquatic gnats and black flies. Neither methoprene nor Bti toxin is harmful to fish, waterfowl, pets, or humans when used according to label directions.
Many products and formulations containing methoprene (Altosid) and Bti (Bactimos, Vectobac) are used by mosquito abatement agencies and other professionals. Homeowners can purchase methoprene as PreStrike. It is sold as granules in shaker bottles. Less than a dozen granules are needed to prevent mosquitoes from developing in a flower pot bottom or bird bath. Less than a teaspoon of PreStrike granules is needed to treat 100 feet of rain guttering. Mosquito development will be inhibited for up to a month in ornamental ponds and similar bodies of water; longer protection is provided in sites that periodically dry out.
Various products containing Bti are available to homeowners (e.g. Mosquito Dunks or Quick Kill Mosquito Granules). Typically, one donut-shaped Mosquito Dunk is recommended per 100 square feet of water surface. The dunk breaks down slowly when wet and releases the insecticide over about a 30 day period. The Mosquito Quick Kill product is a granular formulations that begin to release the Bti toxin more quickly than the dunks, resulting in faster action. While results come more quickly, the residual life of the treatment is generally not as long as the dunk formulation. Granular formulations may be more desirable when treating smaller areas, such as flower pots or tree holes.
With a little careful observation it is fairly easy to see mosquito larvae in clear, shallow water over light colored bottoms. They are harder to see in dark, stagnant water where there is a lot of debris or vegetation. Avoid casting a shadow over the water when inspecting for mosquitoes because the larvae and pupae will dive in response to light changes. They can be captured by quickly plunging a long-handled dipper into the water.