Mosquito Control

The Mosquito Control program begins April 8, 2019 in the City of Portsmouth. Crews from Dragon Mosquito Control 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%)
  • AquaBac 200G (Bacillus thuringiensis israelensis 2.86%)
  • Fourstar MBG (Bacillus thuringiensis israelensis 3.0% & Bacillus sphaericus 3.0%)
  • VectoMax FG (Bacillus thuringiensis israelensis 4.5% & Bacillus sphaericus 2.7%)
  • CocoBear MLO (mineral oil 10%)
  • BVA 2 Mosquito Larvicide Oil (mineral oil 97%)


A truck mounted sprayer will disperse Merus 3.0 (pyrethrins) along roadways. Road spraying will begin in June and may continue into October. It is not possible to predict the schedule for road spraying in advance. The spray schedule is based upon mosquito surveillance data, disease test results and weather conditions.

If Eastern Equine Encephalitis or West Nile Virus is found in or near Portsmouth, then emergency spraying may be conducted using one or more of the following products:

  • Crosscheck plus (bifenthrin 7.9%)
  • Merus 3.0 (pyrethrins 5.0%)
  • Permanone (permethrin 10.0%)

Emergency spray treatments may be conducted at the following locations:

  • Portsmouth High School
  • Dondero Elementary School
  • Little Harbor Elementary School
  • Peirce Island
  • Portsmouth Junior High School
  • New Franklin Elementary School
  • Robert J Lister Academy

It is not possible to predict if emergency spraying will be necessary. The spray schedule is based upon mosquito surveillance data, disease test results and weather conditions. Further communication will be given if emergency spraying is going to take place.

Residents who do not want their property treated may use our 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 us to check it for mosquito activity, email  us at or contact us through our website at and request a survey through the Contact link. There is no charge for this service. Contact us for more information on spray dates, location, materials used, precautions or other concerns.