By Maddy Rohr, K-State Research and Extension news service

MANHATTAN, Kan. — Gardeners may be happy that warmer weather is ahead, but they’re not alone. Kansas State University horticulture expert Ward Upham says the fungus gnat is one of many insects that threaten the health of houseplants.

“Fungus gnats are small insects (1/8 to 1/10 inch long) that are common in high-organic-matter houseplant soils that are kept moist,” Upham said.

Mosquito-like in appearance, fungus gnats are not known for bothering humans or pets. But they do like plants.

“It is actually the larvae or maggots that can injure plants by feeding on the roots,” Upham said.

Symptoms of fungus gnat damage include:

“Using sterile media and avoiding overwatering your houseplants can help prevent infestations,” Upham said. “Existing infestations can be controlled with Bacillus thuringiensis v. israelensis which is sold under the names of Gnatrol and Knock-Out Gnats.”

Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes and gardens. The newsletter is available to view online or can be delivered by email each week.

Interested persons can also send their garden and yard-related questions to Upham at, or contact your local K-State Research and Extension office