For Release February 27, 2005

Winter Gnats Are a Gnuisance

by Chuck Otte, Geary County Extension Agent

It's winter time. Insects are supposed to be dormant or dead! So why do things go flying between me and the TV? What are these little fly like things around my drain? And why is there a gnat in my morning orange juice?!

The fact of the matter is, that many insects are active in the wintertime. Many insects are only in a very light hibernation. So when we get temperatures up into the 50's and 60's, they will warm up enough to start getting active. I even saw a bat out and about a week ago! From now until April or so, you can count on seeing a few more ladybugs and boxelder bugs with every warm spell.

But that's just outside. In your home we have a completely different environment. Most of us keep our homes at temperatures that are warm enough to keep insects quite active. It's actually a bit surprising that we don't have more problems than we do! We often see small tan colored moths flying around our homes in the winter. These are Indian Meal Moths. They are the adult form of a caterpillar that feeds on grain or any grain product. If you are seeing quite a few, you have a problem.

The adults don't do any actual damage, but the females will lay eggs. Use a no pest strip to knock down the adults. But then start searching for the source of the infestation. Anything with a grain base is a candidate. That includes dry pet food, bird seed and decorative dried plant material that contains grain in addition to human food products. Once you find it, throw it out!!

But most of the calls this winter have been from gnats or very small flies, These can be grouped into three distinct, yet similar, groups of small flies: drain flies, fungus gnats and humpbacked flies. To you and me they are all going to look similar. Fungus gnats often come from potted plants. If you bring potted plants in from outdoors in the fall, they are often accompanied by fungus gnats. Of if you are starting a lot of bedding plants from seed in your house, you can expect fungus gnats. These are usually feeding on the decaying organic matter, i.e. peat moss, in the potting mix. Mix up a very light solution of insecticide and water the potting mix with it. This will usually take care of the problem if potted plants are the source.

Humpbacked flies and drain flies can be a bigger challenge. Start looking around the house for any source of liquid or food. If you have plastic bottles or aluminum cans stashed somewhere for recycling, check around these. The residual liquid, especially a sweet liquid, will be a very good food source. If this is the source, move these into an unheated area away from the house.

But the really tricky infestation is often the one that is hidden away, literally down the drain! Many of the drains in our homes are not as clean as you might think. All sorts of residue collects in those drains in a wonderfully moist environment. This collection of crud often starts to decompose and frequently becomes moldy. This mold or fungus is often the food source for the larval or grub life stage of these little gnats and flies. Forget about dumping pesticide down these drains, it won't work. You can use a drain cleaner, preferably one of the foaming ones, to try to remove this food source and infestation. But the best solution is often a simple one. Get a pot of boiling water, a gallon or so, and carefully dump it down the drain as quickly as you can. That much water at once will fill the drain pipe for a few seconds and that will be long enough with hot enough water to kill the infestation at its source! And then that gnuisance gnat will be washed away, along with your problem!


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