Mosquito Prevention During Periods of Heavy Rainfall

~ Submitted by the Bedford Health Department

Mosquitoes are most active in Massachusetts from June through August, but the true determination of mosquito activity is weather-dependent. This summer Massachusetts has seen exceptionally high amounts of rainfall followed by hot and humid temperatures. The Boston Herald recently reported Boston’s rainfall at a high of 8.89 inches for the first eleven days in the month of July. Weather conditions such as this can lead to a significant increase in mosquito activity.

Adult mosquitoes are often found during the day in damp, shady areas where they can find protection from the sun. Mosquitoes need water to lay their eggs and plants to hide in, so they are usually found around water and plants. Mosquito eggs are laid on water or damp soil where the young mosquitoes grow and develop. Mosquito activity tends to increase after periods of heavy rainfall. Mosquitoes are not attracted to actual rainfall but instead are attracted to what the rain leaves behind. Areas where rainwater collects, also known as standing water, give mosquitoes an ideal place to lay their eggs. These eggs will eventually hatch and create an increased mosquito population in your yard.

Most female mosquitoes live for less than two weeks, and most male mosquitoes live for less than a week. However, when the conditions are right such as recent weather conditions in Massachusetts, some mosquitoes will live up to eight weeks. The life cycle of all mosquitoes includes four different stages: egg, larva, pupa, and adult.

Mosquitoes can spread diseases that may make humans and animals sick. Viruses carried by mosquitoes can be transmitted to humans or animals through a mosquito bite. In Massachusetts, the diseases linked to mosquitoes are Eastern Equine Encephalitis (EEE or Triple E) or West Nile Virus (WNV). These viruses can cause illness ranging from a mild fever to more serious diseases like encephalitis or meningitis.

The best way to avoid mosquito-borne diseases is to prevent mosquito bites by taking proactive measures all season long to better protect you, your family, and your neighbors. The most important proactive step you can take after periods of heavy rainfall is to ensure your property is not contributing to mosquito breeding.

Eliminate Sources of Standing Water on Your Property

• Remove, dispose of, or turn over empty containers so they are unable to collect rainwater. Example: Old tires, empty flowerpots, trash barrels, children’s toys, shake out tarps or furniture covers, etc.
• Drill holes in the bottom of containers that are left outdoors so the water can drain out. Example: Trash and recycling containers.
• Clean clogged roof gutters: remove leaves and debris that may prevent drainage of rainwater.
• Turn over plastic wading pools and wheel barrels/ wagons when not in use.
• Keep swimming pools clean and property chlorinated. Remove standing water from pool covers. Use larvicide products in unchlorinated swimming pools.
• Change the water in birdbaths every few days; aerate ornamental ponds or stock them with fish.
• Use landscaping to eliminate standing water that collects on your property.
• Cut shrubs and grass short to eliminate damp areas.
• Always remember to regularly check your yard for containers collecting rainwater, especially after rainstorms!

Use the following additional prevention steps all season long:

• Install or Repair Screens—Keep mosquitoes outside by installing tightly fitting screens on all windows and doors. Avoid turning on outdoor lights during peak mosquito activity.
• Animals and Pets—Keep animal or pet vaccinations and medications current. Speak to your veterinarian about mosquito repellents approved for use for animals. Keep animals indoors or in screened-in areas during peak periods of mosquito activity.
• Be Aware of Peak Mosquito Hours—Dusk to Dawn is peak biting time for many mosquitoes. Consider rescheduling outdoor activities during these hours.
• Avoid Outdoor Areas with Obvious Mosquito Activity—Such as woods and wetlands.
• When Outdoors Wear Protective Clothing – Wear long pants, a long-sleeved shirt, and socks. This may be difficult to do when the weather is hot, but it will help keep mosquitoes away from your skin. Mosquito netting may be used on baby carriages and playpens when small children are outdoors.
• Apply Insect Repellent any time 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.

The Bedford Health Department will continue to work with the Massachusetts Department of Public Health and the Eastern Middlesex Mosquito Control Project (EMMCP) to monitor local mosquito populations for WNV and EEE. To control mosquito larvae, each spring EMMCP conducts a helicopter application of biological larvicide to wetland areas in town and annually each summer the Bedford DPW treats catch basins in town. Additionally, based on acquired surveillance data from up to five mosquito trap locations in town, the EMMCP will continue with truck-mounted spraying events in Bedford to reduce populations of biting adult mosquitoes.

Information about mosquito activity in Massachusetts during 2021 can be found on the Mosquito-borne Disease page on the MDPH website at Mosquito-borne Diseases | Mass.gov.  Facts sheets on WNV, EEE, and other mosquito-related materials are available by contacting the Bedford Health Department at 781-275-6507 or by accessing the Health Department website at Mosquito Control | bedfordma