By now your houseplants are settled in for what looks like it could be a short winter and you are careful not to overwater or water too frequently. Suddenly you see some wilting or yellowing of leaves and small insects hanging around your healthy plants. What are these creatures? They count be fungus gnats.
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. Though adults are mosquito-like in appearance, they do not bother humans or pets. It is actually the larvae or maggots that can injure plants by feeding on the roots. Symptoms include sudden wilting, loss of vigor, poor growth and yellowing leaves. Use of sterile media and avoiding overwatering can help prevent infestations. Existing infestations can be controlled Bacillus thuringiensis v. israelensis which is sold under the names of Gnatrol and Knock-Out Gnats.