by Fran Jurga | 1 September 2009 | The Jurga Report

Greenhead flies can make life miserable for horses and humans around here. (Painting of greenheads attacking a kayaker by Sam Holdsworth from Boston Globe)

Around here, we hate mosquitoes as much as anyone else, but we hold a place in our guts for greenhead flies. These evil insects rise up from the salt marshes for a month each summer. They scare away the tourists. Or eat them alive.

These flies don’t bite or sting, they chomp. And it hurts enough to cause a reflex in horse and human and, believe me, no fly spray will keep them away. Around this time of year I start seeing riders with broken wrists and collarbones because they tried to ride anyway. You can’t blame the horses: it hurts when a greenhead bites!

I suppose the only good thing about greenheads is that you can always blame one for why you fell off or why your horse is behaving very badly. If there’s a picture of you riding in a frame that would have had you expelled from pony club, you can just delete it and say, “Oh, I remember that day! The greenheads were absolutely swarming…” (Surely they were swarming somewhere?)

Even when not ridden, horses show the ill-effects of greenheads: they stamp their shoes right off their feet; most people simply have to keep their horses in or else turned out in fly sheets and leg wraps at night but even that really isn’t enough. They look like ghost horses in the moonlight as you drive by paddocks in August.

If you live near the marshes, farriers don’t want to come and re-tighten shoes or replace a lost one. They know how dangerous it is to work on a horse when biting flies are around, even though they carry jet-speed fans to keep regular flies away.

And this year, they say, is the most benign crop of greenheads in years. A light year.

One local artist has dedicated his entire creative life to depicting the greenheads as some sort of ghastly ghoul, reminiscent of the death-breathers in Harry Potter stories. There’s a film about them now too. It’s a local obsession.

I’m lucky to live on a peninsula that is technically an island and the greenhead flies are pretty much on the other side of the estuary from us. They can’t quite fly across the river (yet) so things are a little less desperate over here.

But something happened the other day at the farmers market that really made me stop and think. As the farms were setting up, they unloaded crates of fruit and vegetables from big panel trucks.

Then my jaw dropped. I watched in horror as the back on one truck opened and out flew a swarm of hungry greenhead flies, hitchhikers from a farm on the other side of the bridge…and now set loose into the pristine fly-free zone on my side of the bridge.

Soon everyone at the farmers market was flinching and slapping and swatting. And swearing. There aren’t supposed to be greenheads here, and they were not pleased.

Will these escapees set up a colony? Is the island doomed? I guess we’ll have to wait and see, but I definitely thought about how insect-borne diseases could easily move around the country in horse vans or hay trucks or even a nice organic orchard’s apple truck.

I had just witnessed a perfect illustration of how disease can spread, even in the presence of a city block of organic produce. It was a sobering illustration of what I write about all the time in this blog: the spread of the midges carrying African horse sickness into northern Europe, the cloak of West Nile virus all over the USA, the connect-the-dot epidemiology of disease outbreaks like foot and mouth disease and EVA.

I think I’ll make an appointment for a flu shot.