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Managing Mosquitoes Using Insecticides

Insecticides used for mosquito management are grouped into two categories:

  1. Larvicides/pupacides are used to control immature (larval or pupal) mosquitoes in aquatic habitats.
  2. Adulticides are used to control adult mosquitoes.

The insecticides used by the DEEP Wildlife Division's Wetland Habitat and Mosquito Management (WHAMM) Program are registered by the U.S. Environmental Protection Agency and the CT DEEP Pesticide Management Program and do not pose any health hazards to humans or the environment when used in accordance with the label.

Larvicides

Larvicides are applied by hand, backpack, or aerial application equipment to mosquito-breeding habitats when there is an abundance of larvae. They are more efficient and effective for managing mosquitoes than adulticides because larvae are concentrated in relatively small, well-defined, aquatic habitats. If larval control methods are successful, the need for adult mosquito management is greatly reduced or eliminated.

Currently, the primary larvicides used by the WHAMM Program are the microbial compounds Bti (Bacillus thuringiensis var. israelensis) and Bs (B. sphaericus) and insect growth regulators containing methoprene. The microbial products release toxins when ingested by the filter-feeding mosquito larvae.

Bti

  • Targets mosquitoes
  • Also controls black flies and some midges
  • Effective life depends on formulation (7-180 days)

Bs

  • Targets mosquitoes
  • Works well in polluted water
  • Effective life depends on formulation (7-180 days)

Insect growth regulators containing methoprene

  • Targets mosquitoes
  • Also used in flea and tick control in pets
  • Longer effective life (several weeks)
  • Mimics an insect growth-regulating hormone, preventing larvae maturation
  • Active ingredient (S-methoprene) breaks down rapidly in UV light

Larvicide Plan (Strategies for the Application of Larvicides to Control Mosquitoes in Response to West Nile Virus in Connecticut - Supplement to West Nile Virus Response Plan)

Pupacides

Pupacides in the form of monomolecular films (MMFs) or oils create a thin film on the water surface which drowns the larvae, pupae, or emerging adults. MMFs break down in about 10 to 14 days.

Adulticides

Adulticides are considered for use by the WHAMM Program to reduce the adult mosquito population when a public health threat from mosquito-borne diseases like EEE or WNV exists. Using adulticides provides an immediate but short-term reduction in adult mosquito numbers. Backpack or truck-mounted equipment is used to create tiny, ultra-low volume (ULV) droplets of insecticide that drift through the swarm of mosquitoes or impinge on vegetation on which the mosquitoes will land. Truck-mounted applications are used in relatively small, localized areas where road access allows adequate coverage. If, however, the public health threat exists in a larger geographic area, where truck-mounted spraying would be ineffective, aircraft can be used to aerially-apply adulticides. The primary adulticides used by the WHAMM Program contain synthetic pyrethroids, such as resmethrin, sumithrin, or bifenthrin. These products contain the same active ingredients as several over-the-counter yard, garden, and pet sprays. They do not pose unreasonable risks to humans or the environment when applied according to the label. Using adulticides is more costly than using larvicides because adulticides are usually applied over larger areas.

The WHAMM Program is actively evaluating new mosquito control products as they become available. New products must provide consistent mosquito control, be nonhazardous to humans and the environment, and be cost-effective. If new products meet these requirements, they are considered for possible use.

Mosquito Management

Mosquito Control Around the Home

Mosquito Control Using Water Management

Content last updated April 5, 2019.