If you’re battling fungus gnats in your seedlings or houseplants, predatory nematodes might be the cleanest biological solution you’re not using. The species most commonly used for fungus gnat control is Steinernema feltiae. These microscopic roundworms actively seek out fungus gnat larvae in the soil. Once they enter the larva, they release symbiotic bacteria that kill the host within 24–48 hours. The nematodes then reproduce inside and continue the cycle. Why this works so well: Fungus gnat da