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The original item was published from 4/14/2023 4:18:41 PM to 4/14/2023 4:20:36 PM.

News Flash

Health Department

Posted on: April 14, 2023

[ARCHIVED] Seasonal Mosquito Larvacide Treatment to begin in April




Seasonal Mosquito Larvacide Treatment to begin in April:  Helicopter will be used to apply a naturally occurring agent to reduce mosquito populations.

April 12, 2023:  In an effort to help reduce the mosquito population in Randolph, the Norfolk County Mosquito Control Commission will be applying a naturally occurring product called Bacillus thuringiensis var. israelensis (Bti).  Bti is a biological larvicide. The trade name of the Bti formulation is Vectobac G (EPA Reg. #73049-10).  

Bti will be applied by helicopter in late April, (depending on the weather conditions and wind speed) to wetlands in Randolph. .   Bti is the only product used to control mosquito larvae in wetlands in Randolph.  A granular form of Bti is applied by helicopter in April at large wetlands to control spring mosquito larvae.

Residents can help reduce the mosquito population in Randolph by “mosquito proofing” their property and avoiding mosquito bites.  Mosquitos lay eggs in standing water, so drain anything that holds water after a rainfall, like unused flowerpots and change water in birdbaths frequently. Install or Repair window screens - Some mosquitoes like to come indoors. Keep them outside by having tightly-fitting screens on all of your windows and doors.

By taking a few, common-sense precautions, people can help to protect themselves: 

Avoid Mosquito Bites

Be Aware of Peak Mosquito Hours - The hours from dusk to dawn are peak biting times for many mosquitoes. Consider rescheduling outdoor activities that occur during evening or early morning. Otherwise, take extra care to use repellent and protective clothing.

Clothing Can Help reduce mosquito bites. Although it may be difficult to do when it’s hot, wearing long-sleeves, long pants and socks when outdoors will help keep mosquitoes away from your skin.

Apply Insect Repellent when you go outdoors.

Use a repellent with DEET (N, N-diethyl-m-toluamide), permethrin, picaridin (KBR 3023), IR3535 or oil of lemon eucalyptus [p-methane 3, 8-diol (PMD)] according to the instructions on the product label.  DEET products should not be used on infants under two months of age and should be used in concentrations of 30% or less on older children.  Oil of lemon eucalyptus should not be used on children under three years of age.  Permethrin products are intended for use on items such as clothing, shoes, bed nets and camping gear and should not be applied to skin. 

Mosquito-Proof Your Home

Drain Standing Water - Mosquitoes lay their eggs in standing water. Limit the number of places around your home for mosquitoes to breed by either draining or getting rid of items that hold water. Check rain gutters and drains. Empty any unused flowerpots and wading pools, and change water in birdbaths frequently.  Install or Repair Screens - Some mosquitoes like to come indoors. Keep them outside by having tightly-fitting screens on all of your windows and doors.

The majority of people who are infected with WNV (approximately 80%) will have no symptoms at all. Approximately 20% of those infected will have symptoms such as fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or skin rash. Less than 1% of people infected with WNV will develop severe illness, including encephalitis or meningitis as demonstrated by high fever, headache, neck stiffness, disorientation and muscle weakness. If you notice any of these symptoms in yourself or a loved one, contact your healthcare provider immediately.

To learn more about diseases carried by mosquitoes and how to prevent a bite, see the following websites below: 

  • Information about WNV and reports of WNV activity in Massachusetts can be found on the MDPH website at    

To learn more about applying repellents or how to dress properly, you may also visit the MDPH website like titled “Mosquitoes and Ticks – they are out in Mass    

If you have any questions concerning this matter, you may contact the Health Department at (781) 961-0924 or the Public Health Commissioner at:   

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