Houseplants may attract gnats in the winter and spring.
When gnats invade houseplants, the little flying pests are irritating. A common gnat to infest houseplants is the fungus gnat, which while a nuisance, is not usually harmful. This flying black gnat breeds and thrives in decaying plant material on the top of the soil. Fungus gnats do not have a long lifespan -- seven to 10 days -- but the females lay hundreds of eggs approximately every week. Gnats are harmless, but the larvae can damage roots and diminish plant vitality. Does this Spark an idea?
Watering
Fungus gnats generally occur in the winter and early spring. Keeping soil as dry as possible helps to kill larvae. Allow the soil surface to dry before watering by placing the plant in the sink so water can fully drain before returning the plant to its tray.
Soil Management
Your best defense is to create inhospitable houseplant environments for fungus gnats. Keep soil free of dead plant material like leaves and other plant debris. Add a top layer of fine peat moss, which can keep gnats away. Before winter, repot houseplants in a mixture of the existing soil, an equal amount of Perlite and a handful of horticultural charcoal to create a free-draining soil environment.
Larvae Control
Controlling larvae is the most effective way to control gnat infestations. Not all insecticides and other soil drench products are widely available in all regions, but are effective when used. Many products are available through mail order. Bacillus thuringiensis var. israelensis or (H-14 strain )is a soil drench bio-insecticide that is very effective, reports Colorado State University Extension. Soil-drench products with non-toxic neem oil are effective against fungus gnat larvae.
Traps
Frustrated houseplant owners may want to use sticky cards to trap adult gnats. Cards must be frequently replaced and do nothing to stop the real problem, which is larvae. Spray insecticides kill adults, but require frequent use of toxic substances. Caring for Houseplants.com suggests home remedies such as leaving red cooking wine in a glass near affected plants to attract and drown the gnats. Repeatedly placing slices of raw potatoes on the soil for two days may kill larvae.
Tags: fungus gnat, Fungus gnats, kill larvae, plant material, soil drench