Greenheads: Why Can’t We Control the Problem?

By Caitlin Dowling, Correspondent
Caitlin is a freelance editor/writer and former news producer for CNN. As a local mom of three, her family can be found enjoying all Newburyport has to offer, from strolling downtown to biking the rail trail to swimming at the beach.
Greenheads, Newburyport

Come July the most common question you will hear in the area is, “Have the greenheads arrived?” These green-eyed horse flies pack a nasty bite, appearing yearly from about mid-July to the first week in August, and make a visit to local beaches near impossible. These bloodthirsty flies not only keep locals from enjoying a day in the sun, but also push away tourists creating an economic impact on coastal towns in the area. So why can’t we control the problem?

Greenheads are found in coastal areas with lots of salt marsh, which is where they lay their eggs. “Very little is actually known about greenheads,” explains Nancy Pau, Wildlife Biologist at the Parker River National Wildlife Refuge. “They only appear once per year for 3 to 5 weeks in July and the rest of their life cycle is spent in the sediment.”

Because greenhead eggs are buried below the surface, it is very difficult to locate the eggs and larva in order to attempt to control the population.

Greenheads only surface once a year, unlike the mosquito for which we have found various means to control. Mosquitos produce multiple generations throughout the season, where greenheads make one single appearance.

While if you ask many locals when greenhead season is, they will most likely tell you it lasts from one full moon to the next. This is not entirely accurate. Experts say that they tend to emerge when the salt marshes flood, which is often, but not always, in sync with the moon. This explains why we only ever have a general idea of when greenheads will arrive and depart.

Greenheads are found in healthy salt marsh areas and some experts believe that they may have a contributing factor to that. Their eggs and larva are also a food source for many coastal birds and fish. Any use of chemicals to eliminate them would only harm the rest of the healthy ecosystem as well. The Northeast Massachusetts Mosquito Control and Wetlands Management District sets over 400 baited “black” box traps in 6 coastal communities: Essex, Ipswich, Newbury, Newburyport, Salisbury, and Saugus. These boxes remove millions of biting flies from circulation each year, but it is still just a small portion of the population. The trapped greenheads also serve as a source of research to further understand these flies.

So the bad news is we still do not have an effective way to control the problem. But the good news is we have learned a lot about these sharp biting flies and discovered ways to protect ourselves. Just because the greenheads are here, doesn’t mean you need to entirely avoid the coastal area!

Tips for Greenheads:

  • Wear light-colored clothing, they are attracted to dark colors.
  • Wear long sleeves and pants when possible, they can not bite through clothing.
  • Plan beach visits on windy days, they have a harder time flying in windy conditions.
  • Or go to the beach for dinner instead of lunch! They are most active from 10 am to dusk.
  • Greenheads are attracted to sweet and salty scents so dry off after coming out of the ocean and avoid perfumes.