Try 1 month for 99¢
Joan Goff quilt

Joan Goff, right, won the Sauk County Master Gardeners Quilt Raffle. She is pictured with Horticulture Educator Phyllis Both.

“They always say time changes things, but you actually have to change them yourself.” — Andy Warhol

A columnist in a local paper had a problem getting rid of fruit flies. She checked all her vegetables and none of them were spoiled. Guess what? Those little flies were fungus gnats.

Fungus gnats live in plant soil, in sewer areas and household drains. They are attracted to carbon dioxide, which is why they fly up right in front of your face. To tell the difference between fruit flies and fungus gnats, look at their color, which is darker than fruit flies. They are about the same size with longer legs and thin antennae. Of course, you need a magnifying glass to see this.

My daughter thinks I am a little strange when I bring the magnifying glass out to look at ticks, fleas, small spiders and fruit flies, and now it’s fungus gnats. I’m fascinated by these small insects. Magnifying glasses are great for kids who are usually open to all new life experiences.

The adults of fungus gnats do not cause problems, but their larvae do. The young feed on the fine root hairs of your plants. They can tunnel into the base of cuttings and can cause leaves to yellow. Their favorite plants are succulents, leeks and onion seedlings in particular.

Most people get fungus gnats in the house when they bring plants indoors in the fall. Another problem is in potting soil purchased for plants and starting seeds. Very moist soil attracts any fungus gnats you may have indoors and they can multiply rapidly. Fungus gnats also can lead to damping off of seedlings since the larvae love the tender roots of young sprouted seeds. Compost and peat seem to be the medium of choice for these gnats. They do not like perlite or vermiculite.

A safe way to help prevent gnats is a layer of sand on top of the soil of your house plants. Use about a half-inch or so. Colored sand can look very nice too. Place containers in areas where you see the most flies.

Another way to catch them is to use yellow cardstock smeared with Vaseline or tanglefoot. Place the cardstock horizontally above the potting medium. It will catch flies as they hatch.

One other way to control the gnats is to mix one part hydrogen peroxide to four parts water. When the top soil of your plant dries, water it with this solution. The fungus gnats will die on contact with the peroxide. This solution will fizz a little when you pour it on the soil but it becomes harmless, so it can be used on herbs and other edible plants you may have indoors.

Another remedy is to sprinkle cinnamon on the soil. The catch is that only Ceylon cinnamon will work and it is rather pricey. Bacillus thuringiensis is also great at killing larvae and is organic. But it has to be a strain called H-14, which is specifically for fungus gnats. It’s popular in greenhouses and goes by the names of Gnatrol or Knock out Gnats.

The big day for the Sauk County Master Gardeners Quilt Raffle was Nov. 3. Joan Goff of Baraboo was the lucky winner and was delighted to receive the beautiful quilt as she is a quilter herself. Many thanks to all of you who purchased raffle tickets.

Contact Phyllis Both by email at or by telephone on Monday mornings at the Sauk County UW-Extension office, 608-355-3253.