Allethrin is a first generation synthetic pyrethroid, which is similar in chemical composition to one of the components found in natural pyrethrin, Cinerin I. This insecticide functions in much the same way as natural pyrethrins by affecting nerve function in insects and is not a cholinesterase inhibitor. Although more stable to heat and light, its persistence in the environment is also limited…

Bacillus sphaericus is a commonly occurring spore-forming bacterium found worldwide in soil and aquatic environments. Certain strains of this bacterium have been found effective against some species of mosquitoes. Like the larvicide Bti (Bacillus thuringiensis var. israelensis serotype H-14) this bacterium forms protein crystals that can destroy the mosquito larva’s gut lining causing death…

Bacillus thuringiensis var. israelensis serotype H-14, also known as Bti, is a strain of bacterium that produces protein crystals, which are toxic to mosquitoes, biting black flies and a few species of midges. These crystals act as a stomach poison, being activated by the alkaline digestive enzymes found within the larval mosquito gut. The gut wall begins to break down (dissolve) within a few…

BVA-2 is a highly refined petroleum-based product that is used only on the pupal stage of the mosquito. This is a last resort material that is used to prevent adult emergence. It works by changing the surface tension of the water surface, causing both the larval and pupal stages to drown.

Methoprene, an insecticide known as an insect growth regulator, is a true analog of a mosquito’s own growth or juvenile hormone. This insecticide works by inducing damaging physical changes to second, third and fourth stage (instar) mosquito larvae preventing the successful emergence of adult mosquitoes from the pupal stage.

Pyrethrins, extracted from chrysanthemum flowers, are a group of naturally occurring compounds with excellent insecticidal activity. This insecticide was first used as a powder around 1800 and has been used to control mosquitoes since the 1880’s. Pyrethrins are currently used in sprays, powders, mosquito coils and in truck-mounted ultra low volume (ULV) applications.

Synthetic pyrethroids are synthetic derivatives of natural occurring pyrethrins and are used by the District to control yellowjackets and adult mosquitoes. First generation synthetic pyrethroids (e.g. allethrin) are more active than natural pyrethrin but are unstable in sunlight, breaking down very quickly. Second generation synthetic pyrethroids are more resistant to degradation by light and air…