My office has an infestation of black flies.  Apparently the fly’s seek warmer environments as the weather gets cold.  This includes things like crevices of trees and other places that will provide some protection from the elements, like our warm leaky building.

Older buildings leak heat and this attracts the flies.  If your building is near open fields or parks where they breed in warmer weather and your building is not well sealed, as could be the case for many buildings on a historic university campus ( lots of open fields and areas fly’s like to breed as well), you could be at risk of an infestation.

What to do?

Apparently one good alternative is to fumigate in the fall (i.e., around now).  This will clear out the place and given there are not many new fly’s hatching outside in this weather, the problem is put off until next fall when the new batch of spring and summer fly’s seek warmth and the cycle starts all over.

Of course, you could upgrade the buildings envelope to improve it’s seal against the outside coming in.  This would be an environmentally sound approach as well reducing the amount of energy required to heat and cool the buildings interior.  Probably more environmentally sound than pesticide as well.

Oh Pesticide

One fine colleague pointed out that there are no known or documented cases of disease transmission by black fly’s while pesticides probably are not good for you.

I guess if you don’t mind having black fly’s wander on your sandwich at lunch time or sit on the rim of your coffee cup they could be tolerated.  I mean you probably won’t get sick, I find it a bit unappetizing though and that cup of coffee, well – down the sink.

So if I weigh pesticides versus tolerating these little black pests I do lean toward pesticide.  My preferred solution though would be better installation of the building.  This would reduce heat leakage which attracts the fly’s as well as reducing their entry points to the building.