Gnats in My Houseplant Sand

Gnats

• If you have a problem with gnats around your houseplants, the most likely insects involved are fungus gnats. Fungus gnat larvae can damage plants as they will consume the living root hairs and feeder roots of your plants, according to the Colorado State University Extension, which can lead to a cycle where your plants become stressed and lose foliage, the foliage falls onto the soil surface and the leaves decay to provide additional food for gnat larvae. Drain flies may be mistaken for gnats. You may see these pests around plants kept in kitchens or bathrooms near household drains.

Moisture and Decay

• Fungus gnats and drain flies are attracted to the same two things in the environment around your plants: moisture and decaying vegetation. Regularly remove dead material from around your plants. If your plants are sitting in trays of water to generate humidity, remove the water until you get the pest problem under control. Rethink how you water your plants, and allow plants that will tolerate the treatment to dry out between waterings.

Soil

• Repot your plants, which will help get rid of eggs and larvae in the soil, but the biggest benefit comes in replacing the growing medium. According to the Colorado State University Extension, as medium ages, it holds more water. Fresh material offers better drainage, and these dry conditions create an environment hostile to gnat maggots. As sandy soils drain freely, plants grown in them dry quickly but may require more frequent watering. Switch to a different growing medium if your plants tolerate other soil types.

Treatment

• Approach your pest problem from several fronts at the same time. Neither of these types of insects fly well or far, so the best treatments are those applied in the areas where you encounter the pests. Install yellow sticky traps to reduce adult gnat populations so there will be fewer pests around to lay eggs or annoy humans. Use a pyrethroid-based insecticide to kill adult gnats and drain flies; this type of insecticide lasts longer and remains effective longer. Find and eliminate any other areas in your home where drain flies may breed. Treat your drains with a product designed to remove the biofilm coating inside the pipes, or scrape the drain and pipe walls clean, then flush them with boiling water and bleach, suggests the North Carolina Cooperative Extension.