Sciarid Fly (Fungus Gnat) Control Nematodes 12sq.m.Sciarid Fly (Fungus Gnat) Control Nematodes 12sq. m are microscopic parasitic worms that seek out sciarid fly larvae in the soil, feed on them and multiply inside to stop them damaging your plants. Sciarid fly (fungus gnat) is a common pest of indoor plants including houseplants, conservatory plants, and greenhouse crops. The larval stage attacks plant roots, causing significant damage and potentially killing affected plants. Nematodes are naturally