Mosquito Control

The Mosquito Control program begins April 5, 2021 in the City of Portsmouth. Crews from Dragon Mosquito Control, Inc. will be checking swamps, salt marshes, woodland pools, ditches, catch basins and other shallow, stagnant water for mosquito larvae.

When mosquitoes are found, the following larvicides may be used:

VectoBac (Bacillus thuringiensis israelensis 2.8%)
Natular (spinosad 2.5%)
Fourstar MBG (Bacillus thuringiensis israelensis 3.0% & Bacillus sphaericus 3.0%)
VectoMax FG (Bacillus thuringiensis israelensis 4.5% & Bacillus sphaericus 2.7%)
VectoPrime FG (Bacillus thuringiensis israelensis 6.07% & methoprene 0.10 %)
CocoBear MLO (mineral oil 10.0%) BVA 2 Mosquito Larvicide Oil (mineral oil 97.0%)

Citywide nighttime road spraying is not planned. If Eastern Equine Encephalitis, Jamestown Canyon Virus or West Nile Virus becomes a public health threat, spraying may be conducted at the schools, and parks. It isn’t possible to predict if emergency spraying will be necessary. The decision to spray is made in consultation with city officials and is based upon mosquito surveillance data, disease test results and weather conditions. Additional notification will be given in the unlikely event emergency spraying is scheduled.

Residents who do not want their property treated may use the No-Spray Registry online at or write to Dragon Mosquito Control, P.O. Box 46, Stratham, NH 03885. Be sure to include your name, physical address, phone number, a description of your house and acreage. If you have wetlands on your property and you would like Dragon Mosquito to check it for mosquito activity, email or contact them through their website at and request a survey through the Contact link. There is no charge for this service.