Chemical Control and Pesticides

Chemical control, a short-term strategy, involves the application of insecticides either by hand (hand cans, granular spreaders, ATV’s, or truck mounted spray rigs), or by aircraft. The chemicals used by this District are listed below. None of these materials has any significant residual activity (pyrethrin degrading within four to six hours, methoprene persisting for about three days, and BVA-2 lasting less than two days).

A list of the pesticides used by the District can be found on our Pesticide Summary page. The pesticides we use are designed to be target specific and cause the least environmental disruption possible when used at the label rates dictated by State and Federal law. For more information you can go to the following links.

Allethrin

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 (Bs)

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 (Bti)

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 Larvicide Oil

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

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.

Pyrethrin

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

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…

Pesticide Summary

Note: Oral and Dermal LD50 data was taken from Manufacturers’ Material Safety Data Sheets.

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