Town Mosquito Control
The Town's mosquito control contractor applies a biological insecticide (Bacillus thuringiensis israelensis; Bti) to portions of Town salt-marshes and Town-owned properties in which larvae are present, based on the inspections noted above. This Bti is placed weekly during the warmest part of the summer, and biweekly in the spring and fall. In addition, the contractor places another biological insecticide (Bacillus sphaericus) into catch basins in which there is a likelihood of mosquito breeding. The catch basins are treated several times per year, beginning in mid-June and ending in mid-September. These insecticides attack only mosquito larvae, and do no harm to other aquatic organisms.

Bti is a cousin of other varieties of Bt that are commonly used in gardens to control cabbage loopers and other caterpillar pests. Bacillis sphaericus is targeted to the Culex species of mosquito, which are some of the most competent vectors of West Nile virus, and thrive in dirty waters with high organic contents, such as catch basins.

Pesticide Spraying
Commercial ground-level spraying to control adult mosquitoes is the least effective and the most environmentally controversial form of mosquito management. The Town does not normally conduct such spraying; however, if a significant mosquito-borne threat to public health were detected in town, the Town Health Department and First Selectman, in consultation with the State DEP and Department of Public Health (DPH) could recommend ground-level spraying to control adult mosquito populations in targeted areas. In that case, and after alerting the public, a mild insecticide would be sprayed into the air of the affected area.

The insecticide would probably be a pyrethroid, applied by a truck-mounted ultra-low volume mist sprayer. This technique ensures the maximum coverage of the area with minimal insecticide. Pyrethroids are synthetic versions of natural insecticides derived from chrysanthemum flowers and exhibit very low toxicity to mammals. These insecticides break down in sunlight in 4 hours and leave no residue.

Mosquito Control Activities for Residents
The Town’s mosquito control program does not directly address fresh water mosquito populations on private property. That task falls to property owners and the simple act of eliminating standing water can have a substantial effect on mosquito populations. During the warmest months, water that stands for more than 5 days will probably be actively breeding mosquitoes. 

Mosquitoes that have been shown to most commonly carry West Nile virus and eastern equine encephalitis do not normally travel more than few hundred yards in their lifetime, and thus, individual actions on each property are important in controlling the potential spread of these diseases. If mosquito populations aren’t sufficiently controlled in the larval stage, large numbers may develop into adults in just a few days during the warmest weather.
  • Dispense of water-holding containers, such as ceramic pots, used tires, tire swings.
  • Drill holes in the bottom of containers such as those used for recycling.
  • Clean clogged roof gutters.
  • Turn over objects that may trap water when not in use, such as wading pools and wheelbarrows.
  • Change water in bird baths on a weekly basis.
  • Clean and chlorinate swimming pools, and when not in use, cover pools.
  • Use landscaping techniques to eliminate areas where water can collect on your property.