Fungus gnats are a common problem. An infestation can be recognized by swarms of tiny insects appearing around recently watered plants. These tiny flies are attracted to damp soil and will lay their eggs there. Once the eggs hatch, the larvae stay in the top 2 to 3 inches of soil and feed on fungus and decaying plant material. When left unchecked the larvae will feed on the plant’s roots causing damage to the plant. Though too small to see, fungus gnats can be identified by their dark gray-black color, transparent wings, long legs and long antennae. Control them as soon as possible to prevent them from spreading to neighboring plants. Following are tips to prevent and remove infestations.
Always use a pot with drainage holes. Water sitting in the soil without draining will encourage fungus gnats as well as disease.
Top the soil with rock. Apply a good layer of porous rock to the top of the soil. The rock will discourage the fungus gnats from laying eggs. Lava rock, pumice or pea gravel are good choices.
Use terracotta pots. Terracotta is porous and allows the soil to dry out more quickly than plastic pots. Fungus gnats tend to stay away from dry conditions.
Let the soil dry out completely between waterings. Frequently check the soil with your finger. Once it is completely dry, water it well. However, do not let the soil stay dry for long as your plant may dry out. This method is not recommended for ferns, palms, peace lilies, maranta and calathea. They need the soil to retain some moisture.
Treat with hydrogen peroxide. When it’s time to water, use a solution of 1 part hydrogen peroxide to 3 parts water. The hydrogen peroxide will kill any fungus in the soil that attracts and supports the fungus gnats. Use as needed.
Use sticky traps. Always keep sticky traps around your indoor plants to trap any new fungus gnats before they lay their eggs.
