May 24, 2023 / Seasonal Pest Control

Spring Scourge of the Black fly: What can I do to protect my family?

black fly swarm

When the spring tulips begin to emerge in New England, the skies will begin to cloud with a small but formidable insect named the black fly.  As spring progresses and tulips drop their petals, black fly numbers expand and aggressively patrol the lower airways in a relentless search for a blood meal that is required to produce the next generation of flies.  Black fly swarms have been known to chase the biggest and bravest of us off the trail, from the stream, and even from our own backyard to seek protection in shelters to avoid the extreme nuisance and bloodletting of these tiny vampires.  They will stop at nothing to bite and feed on any warm-blooded mammal within their zone.  Their ferocity is unmatched in nature; just ask anyone from Maine.

Where do black flies breed?

Black flies are aquatic insects, just like mosquitoes, and their eggs are deposited in water where the larval stages live and develop.  There are about 40-50 species of black fly present in our region.  Only a couple of species are human biters.  Unlike mosquitoes that require stagnant water sources to develop, black flies can only develop in relatively clean water associated with streams, rivers, and mountain snow runoffs.  They will not breed and develop in lakes, ponds, pools, or other standing water. Bodies of water where black flies emerge could be many miles away from residential settings. 

How can such a small fly pack such as big punch?

Black fly adults, females only, are equipped with a pair of powerful serrated mouthparts or jaws.  You can feel black fly bites because females puncture the skin with saw-like blades then rip the wound open to allow the blood to pool on the surface.  Female black flies are not equipped with the same piercing-sucking mouthparts that mosquitoes possess that enable them to drink the blood through a siphon.  Instead, black flies use their spongy mouthparts to lap up the pooled blood and hopefully escape before you kill it. 

Additionally, during the feeding process, saliva passes into the wound and many people will experience a strong itch irritation long after the bite occurred.  Some people will suffer from black fly bites weeks after the initial wound occurred.  The big risk here is with infection of the wound caused by intense itching and scratching.  Seek medical advise if the itching becomes unbearable to prevent serious secondary infections.

The bright side of black flies:

  • Black flies are an important part of aquatic ecology and are favored food sources of trout. 
  • The adult flies are eaten by birds and bats. 
  • A healthy black fly population is a sign of good water quality.  Most species cannot tolerate polluted water.
  • They do not carry disease in New England.

What can I use to treat my yard for blackflies?

Black fly season is a given event in New England just like mud season.  Their season typically runs from Mother’s Day to Father’s Day and by July, the big swarms are reduced to more tolerable numbers of biters. 

The bad news is that nothing will work to keep black flies from your outdoor spaces until their season ends.  In order to effectively manage their populations, the rivers and streams would need to be treated with a larvicide material.  Rivers and streams are protected by federal and state agencies and permits are required to treat all bodies of water.  The treatment would then require the use of aircraft to make the application.  Government agencies would only allow a permit if black flies posed a serious health threat to people or livestock, which they currently do not.   

How do I protect myself and family from black fly bites?

  • Wear light-colored clothing.  Black flies are attracted to dark-colored materials because the animals they prefer to bite have dark fur.
  • Wear long sleeves and pants that cover all exposed skin.
  • Investigate permethrin treatments for gardening, fishing, and hiking clothes.  There are do it yourself products and retail clothing that is factory impregnated with permethrin available.
  • Use an EPA approved insect repellent for all exposed skin.  Be thorough and don’t forget about the scalp line, behind the ears, and under watchbands.  Remember that repellents containing the active ingredient DEET will damage synthetic materials and plastics.  Repellents containing the active ingredient Picaridin are very effective DEET alternatives and are available in lotion formulations which allow for more thorough coverage than alcohol-based sprays.  Always follow skin repellent label directions for health safety and maximum effectiveness.
  • Avoid outdoor activity during cloudy days, which black fly seem to prefer.
  • They only bite during the daylight hours; black flies are less active during early morning hours.

We hope that you can utilize the bite prevention advice offered here to protect yourself and family from black flies ruining your spring and summer outdoor activities.  This advice also works for ticks and mosquitoes.  While we cannot provide any effective services for black fly management at your property, JP does offer mosquito and tick management programs that will allow you to enjoy your backyard.

At JP Pest Services, our Professional Service Specialists are very knowledgeable and expertly trained to conduct site inspections that identify pest activity and avert future problems.  Our goal, through an Integrated Pest Management (IPM) approach, is to eliminate the current infestation and prevent the next one.  The moment you let your guard down, pest invaders seeking food, water, and shelter will fill the void!