Public Statement by the Winthrop Board of Health

Regarding the Cancellation of the Mosquito Spraying Scheduled for Thursday, August 9, 2018

The Board of Health unanimously voted on 08/07/2018 NOT to authorize the adulticide spraying (i.e. spraying of adult mosquitos using pesiticide) in Winthrop scheduled for August 9, 2018.

The Board’s decision was determined by the following information:

Who is providing mosquito management in Winthrop?
Mosquito control in Winthrop is managed by the Commonwealth of Massachusetts via the NorthEast Massachusetts Mosquito Control and Wetlands Management District (NEMMC). Their services provided to Winthrop include, but are not limited to, Mosquito Surveillance, Virus Intervention, Ground Larviciding (i.e. treatment of mosquito larvae using biological agents), Ditch Maintenance, Wetlands Management and Property Inspections. They are the only entity allowed to perform adulticiding (i.e. treatment of adult mosquitos using spraying of pesticides) in our district.

When is spraying (adulticiding) indicated?
Per the 2018 Best Management Practice Plan for Winthrop issued by the NEMMC, spraying is ONLY to be performed when viruses have been identified in local mosquitos (virus intervention) and requires approval by the Board of Health. Residents may not request spraying by NEMMC directly.

What are the MA Department of Public Health (DPH) recommendations for spraying (adulticiding)?
Due to the toxic effects of the pesticide used to the environment (it is highly toxic to bees and harmful to water species like fish), DPH urges communities to limit spraying of pesticides as much as possible and reserve it for high risk virus intervention, Pesticide spraying (adulticiding) has to be performed during the night, when bees and other pollinating insects are not active.

What are mosquito counts this year in Winthrop?
Official mosquito trap counts in Winthrop in 2018 to date are down 73% compared to 2017 counts.

What is the current risk for West Nile Virus (WNV) and Eastern Equine Encephalitis (EEE) in Winthrop?
Weekly testing for WNV and EEE is being done, and no WNV or EEE  have been detected in Winthrop to date in 2018. Currently, our district is placed on moderate risk with regard to WNV, due to the recent detection of WNV in a bird-biting mosquito in Lynnfield. No adulticide application was performed in Lynnfield, as subsequent testing was negative. A moderate risk level does not justify adulticide application.

What caused the recent surge in mosquitos we are experiencing in some areas of Winthrop?
We are aware of the recent surge in mosquitos in certain areas of the town, leading to many calls from residents, predominantly living in the Highlands. The vast majority of these day-time active mosquitos are salt marsh mosquitos brought into town by the wind from surrounding marshlands. Hence, spraying (adulticiding) for flying species after sunset in Winthrop would be ineffective for controlling these, and would not result in significant relief for residents. In addition, these species are not typically WNV or EEE carriers.

What is being done to prevent mosquito breeding in Winthrop?
Larviciding (targeting immature mosquito forms (larvae)) is being intensified in wetlands, sewers and other areas of concern (such as Nahant Ave and others) are being intensified and will continue throughout the summer. We are in discussions with NEMMC regarding additional measures the town can take to decrease mosquito breeding.

We hope these answers clarify the Board’s decision to cancel the spraying at this time. Should we receive notice about an increased risk for WNV or EEE to Winthrop residents, we may authorize adulticide treatment (spraying).

What you can do:

  • Inspect your property and your neighborhood for any pools of standing water (such as gutters, barrels, tires etc), as mosquitos will breed in those after only 4 days. Notify Winthrop's Department of Inspectional Services when you notice pools of standing water on public property so they can be removed. the town can issue citations to residents who do not remove such containers on their property.
  • Wear protective clothing and/or apply mosquito repellent containing DEET when you spend time outside during the evening hours, when virus vector mosquitos are most active. DEET products should not be used on infants under 2 months of age. Children older than two months should use products with DEET concentrations of 30% or less. In addition, oil of lemon eucalyptus [p-menthane 3, 8-diol (PMD)] has been found to provide as much protection as low concentrations of DEET, but should not be used in children less than 3 years of age.

We encourage you to attend our next Board of Health Meeting on August 14, 2018 at 6 PM.

Further resources can be found here:


Bill Schmidt, Chair

Dr. Astrid Weins, Vice-Chair

Susan Maguire, Member