City Starts Mosquito Control Program Monitoring April 8, 2024

April 5, 2024

The City of Portsmouth’s Mosquito Control Program begins monitoring on April 8, 2024. Crews from Dragon Mosquito Control, Inc., the City’s contracted service, will be checking swamps, salt marshes, woodland pools, ditches, catch basins and other shallow, stagnant water for mosquito larvae.

Citywide night-time road spraying for adult mosquitoes is not planned. Any decision to conduct emergency spraying of adult mosquitoes on City-owned property is made by City officials based on the mosquito surveillance data, disease test results, and weather conditions provided by Dragon Mosquito Control. Diseases such as EEE and West Nile Virus are generally found in mosquitoes during the latter part of the summer and early fall. Residents will be advised in advance if spraying is planned.

However, when mosquito larvae are found, treatment may occur using one or more of the following:

  • VectoBac (Bacillus thuringiensis israelensis 2.8%)
  • VectoBac 12 AS (Bacillus thuringiensis israelensis 11.61%)
  • Fourstar Bti CRG (Bacillus thuringiensis israelensis 10%)
  • Natular (spinosad 2.5%)
  • BVA 2 Mosquito Larvicide Oil (mineral oil 97.0%)
  • SunSpray MLO (mineral oil 98.8%)

Residents who do not want their property treated can sign up with the No-Spray Registry at or write to Dragon Mosquito Control, Inc., P.O. Box 46, Stratham, NH 03885. When writing, residents should be sure to include name, physical address, phone number, the color of the house and acreage or road frontage.

For more information on spray dates, location, materials used, precautions or other concerns, call 603.734.4144 or email

Mosquito biting hand