Can be used on all indoor house plants, tropical plants and any time you add more potting soil to your plants. Fungus gnat control nematodes are microscopic worms which seek out larval stages of various fly and other dipteral insects which develop in the soil. Easy to apply with a watering can or hose-end sprayer for outdoor uses. Ideal preventative treatment for tropical plants which are brought indoors after the outdoor gardening season is over. Fungus Gnat Control Nematodes work on a variety of fly larvae. Each box contains 2 applications of beneficial nematodes to control the larval stage of fungus gnats in indoor potted plants. Simply mix your nematodes into a watering can and drench the soil of all indoor plants. Follow up with the second application in 7-10 days for a complete natural way to kill fungus gnats.