In mosquito control, a larvicide is a pesticide that is especially designed to kill mosquito larvae during their aquatic life stage. Contact poisons, stomach poisons, growth regulators, and biological control agents are all examples of larvicides.
The National Environment Agency (NEA) in Singapore places a strong emphasis on reducing the Aedes mosquito‘s breeding grounds as the main goal of its dengue control initiatives. Everyone has a part to play in the fight against mosquitoes. Simple everyday actions that we can all do to prevent mosquitoes from establishing a presence in our neighbourhoods include inverting pails and plant pot plates, changing the water in vases on a regular basis when they are not in use, and more.
Despite everyone doing their part, there are still mosquito breeding grounds that are out of our grasp. This is when pest control professionals must intervene to supplement with larval control methods and the following are some examples of pesticides that are approved for use as larvicides.
Biological Larval Control
In Singapore, the naturally occurring soil bacterium Bacillus thuringiensis israelensis (or Bti for short), is commonly utilised as a biological pest management agent to destroy mosquito larvae and certain midges.
When registered as pesticides, they can come in granular form, in the shape of donuts or individual blocks. Examples of NEA-registered larvicides that contain Bti include the trade names Vectobac, Mosquito Dunks, AQUABAC, Moskil, MOUSTICIDE, Relief BTI.
Bti for larviciding is employed in locations where there is stagnant water. When mosquito larvae consume the bacteria, crystalline toxins are created, which harm the digestive tract and cause death. When used as directed, Bti will only last a few weeks in water and pose no risk to people, unintended animal species, or the environment.
Chemical Larval Control
Temephos
Temephos, an organophosphate, can be used in chemical larviciding and is beneficial when the larvae have gained resistance to bacterial larvicides.
Examples of NEA-registered larvicides that contain temephos include the trade names Abate, Clovertemph, Temebate, Ecoforce, Spar, Laevikil, Relief T.
Because of the minimal amount required and the rapid pace at which temephos degrades in water, this sort of larvicide poses no excessive health risk to humans. However, at high dosages, it might produce nausea and dizziness.
Temephos causes no significant harm to terrestrial species but there is a hazardous risk for non-targeted aquatic species. Therefore, it is important to utilise temephos for larviciding carefully and cautiously.
Cypermethrin
Cypermethrin (CP), a synthetic pyrethroid, which is known to be toxic to mosquito larvae and pupae is another example of chemical for larval control.
When Cypermethrin is in the form of a Emulsifiable concentrate (EC), the formulation is diluted with water to form a spontaneous emulsion and then sprayed on water puddles for larval control.
Anti-Mosquito Oil for Larval Control
Applying oil on the water surface is one of the traditional modes of larval and pupal control. In Singapore, anti-malaria oil derived from petroleum is commonly used as larvicide/pupicide. These gas oil hydrocarbon solvent and surfactants combat mosquito larvas and pupas through suffocation.
When applied to stagnant water, it will deposit a thin layer of oil on the water’s surface, thereby cutting off the mosquito larvae and pupae’s oxygen supply so they cannot survive.
Leverage Mosquito Behaviour for Larval Control
The In2Care mosquito station uses the adult mosquitoes to effectively spread larvicide to all breeding sites within the vicinity.
The active ingredients in the In2Care trap/station contain the larvicide Pyriproxyfen (PPF), which is an NEA-registered and WHO-approved juvenile hormone analogue; a chemical that inhibits the mosquito’s growth hormone and stops larvae from developing into adult mosquitoes. In addition, the active ingredients contain an approved fungus that kills the mosquito several days after exposure which helps prevent disease transmission.
Only tiny amounts of larvicide will spread to other breeding sites, which is enough to kill mosquito larvae (as <10 ppb PPF works well) but not enough to cause risk for non-target organisms like fish or mammals.
In this way, these traps offer an effective 24/7 mosquito control option without drastic use of chemicals in the entire environment. Each trap effectively covers an area of 400 square metres which equals 4300 square feet. The In2Care Trap/Station offers effective long-term 24/7 mosquito control with reduced need for additional periodic chemical spraying.