Houston County Extension ANR

Biting Gnats

Recently the Extension Office has been answering a lot of calls from angry homeowners who are being attacked every time they go outside in their yards. Because of the numerous calls and my own personal encounter, I decided that it was time to do a little research on this pest.

Not that it is any comfort, many areas across Georgia are seeing large populations of gnats (the normal annoying kind that fly around your mouth and eyes) and of the insect known as a black fly or a Buffalo gnat (the biting kind).   Florida experiences more occasional outbreaks than Georgia since the population explosion is often triggered by extreme rainfall.  The breeding ground is oxygenated water sources; therefore, adults are usually associated with slow moving streams, creeks, or rivers.  This is different from the still, standing water that invites mosquitoes to breed.

Livestock, family pets, and humans can all fall victim to the vicious bite of the black fly.  The flies prefer to feed in the daytime and seem to like the head, ears, and shoulder areas simply because these spots are warmer on the body.  The female fly actually feeds by cutting into the skin, injecting an anticoagulant, and then enjoying the blood that forms in the hole she makes.  The anticoagulant often causes mild to severe allergic reactions in sensitive individuals and the bite can itch and persist for a number of days.  These bites can be as painful as the bite of a fire ant.

Insect repellents containing DEET are not effective in preventing black fly bites.  In fact, research shows that DEET may actually attract the black flies.  Products containing a permethrin designed specifically to repel ticks will work, but these chemicals are designed ONLY for clothing application, not to skin. There are some herbal-based treatments containing geraniol or citronella oil that seem to work, too. I would never want to wish for a drought, but reduced amounts of rainfall that is feeding our streams and creeks would help reduce the black fly population.

extension.uga.edu and Teddie Berry, Houston Horticulture Program Assistant