Fungus gnats mere nuisance

Q. I found these small little specks of bugs crawling on my windows in the sunlight. What are they? I’ll bring a few of them into the clinic the next time I am out.

Shirley from New Middletown

A. First, thank you for bringing in samples. Identification would have been next to impossible with only a verbal description of the insects you brought in.

The little specks you found on your windows are fungus gnats. Fungus gnats are dark-winged members of the Diptera order, like their relatives, the flies. They are found throughout the United States and occasionally become a nuisance indoors when adults emerge in large numbers from potted plants or flower boxes. Houseplants brought inside in the fall and/or new house plants purchased are the most likely cause for the infestation of your home. Adults are attracted to lights and are often first noticed at windows or flying around potted plants, exactly like you found them.

Fungus gnats spend most of their life cycles as larvae and pupa in the soil where the larvae feed on fungi, but they also will feed on plant roots. When they feed on plant roots, they can cause a decline in plant health. A symptom of this decline would be a yellowing of the leaves. Their last life cycle stage is the adult stage where they emerge from the soil and mate. Adult fungus gnats do not damage plants or harm people – they are simply a nuisance (and good at that!)

Prevention is the best control for fungus gnats. Inspect any plant for signs of the gnats, such as adults on the plant or yellowing leaves before buying a plant or bring a plant into your house. Do not allow a buildup of plant material around the plant or over mulch it. Fungus gnats like a moist soil. Thus, a control option is to allow the soil to dry out, but resume watering before the plant becomes stressed. Finally you can repot the plant. When repotting use potting media that contains only completely composted organic matter. This will eliminate the possibility of the reintroduction of the gnats into your home.

There are pesticides for fungus gnats. But, because they are only a nuisance in the home, chemical controls are not recommended.

To learn more about these annoying insects and for more control options, visit go.osu.edu/fungusgnat

Today’s answer is provided by David Sprague, OSU Extension master gardener volunteer. Call the office hotline at 330-533-5538 to submit your questions. Regular clinic hours begin April 4, on Mondays and Wednesdays from 9 a.m.-noon.