Small insects similar to flies, gnats usually appear in summer, often swarming about peoples’ heads. These delicate black insects, about 1/8 inch long, are more of a nuisance than anything else, although in large numbers they can become serious pests in greenhouses, where they feast on plant roots. Getting rid of gnats is simple, although it takes some perseverance to make sure they do not return.
Gnats have a short life cycle but reproduce prolifically. With a life span of about four weeks from egg to adult, each female can lay 200 to 300 eggs and cause havoc all year. The larvae are legless and threadlike with white bodies and black heads, and typically live in the top 2 to 3 inches of houseplant potting soil.
Gnats are often called fungus gnats because they are attracted to rotting fruit and vegetables and moist areas, including decaying plant materials. Identifying the source and eliminating it goes a long way toward keeping gnats out of your home. Throw away overripe fruit and soft potatoes or keep them in the refrigerator. Don't over-water houseplants and always drain excess water from plant containers. Take items to the compost pile right away, rather than keeping them inside the house. Dim the lights because gnats are attracted to windows and light fixtures.
If the gnat infestation is severe, apply a ready-to-use neem oil product. Spray the neem oil over the top of the potting medium. The neem oil will not harm the plant and kills emerging adults. Since neem oil quickly dissipates from the soil, reapply the product every two to three days until the gnats are no longer problematic.
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