Homeowners often discover small flies hovering around their houseplants. Many of these insects are introduced into the home through insect-infested plants. Avoid bringing new plants directly into your home. Instead, quarantine the plant for a period of seven to 10 days and monitor it for insect activity. While there are many insects that affect houseplants, the most common flies are whiteflies and fungus gnats.
Fungus gnats are a common houseplant pest. These tiny flies are delicate, have dark wings and closely resemble mosquitoes. Fungus gnats live in the potting soil of infected houseplants. While they are troublesome, they do not bite humans or feed on plant leaves. Fungus gnats reproduce by laying wormlike larvae in the soil of indoor plants. The larvae of this pest lives in the top 3 inches of potting soil and feeds primarily on algae and fungi.
Fungus Gnat Control
Controlling fungus gnats in houseplants is best accomplished by regulating the moisture level in houseplants. Always allow the potting soil to dry completely between plant waterings, as excess moisture promotes fungus gnat development. Repot plants that are retaining too much water and take long periods for potting soil to dry. Heavy infestations of fungus gnats may require insecticide applications for control. Apply insecticides directly to the potting soil, to eliminate adult fungus gnats as they emerge.
The greenhouse whitefly is a common pest of houseplants, as well as vegetable crops such as cucumber and tomato. Whiteflies are tiny, winged flies that are covered in a fine wax. Adult whiteflies lay their eggs on the leaves of the houseplant, which hatch in three to seven days. When nymphs hatch, they feed on houseplant leaves which damages the plant. Nymphs feed on houseplants for up to four weeks before becoming inactive for several weeks. After this period, they emerge as adult whiteflies. The whitefly nymphs are responsible for the majority of feeding damage to the houseplant.
Placing yellow sticky insect tape around the home, may help reduce whiteflies. Vacuuming small houseplants can reduce or eliminate adult whiteflies. Horticultural oils, insecticidal soaps and neem oil are all effective against most whiteflies. Spraying your houseplants with insecticides containing the active ingredient imidacloprid, successfully controls whiteflies on houseplants.