Gnats in houseplants, though harmless to humans, can be an annoying nuisance. Houseplant gnats are often caused by a specific type of gnat that is notorious for infesting the soil of indoor plants. Overwatering is a common cause of gnat infestation in indoor plants. Learn the symptoms of a houseplant gnat infestation and what to use to prevent and control gnat problems in indoor plants.
Gnat infestation in indoor plants can appear as a number of small grayish gnats walking around on the houseplant soil. Other indications that a houseplant may have a gnat infestation include finding gnats around the house. The gnats that infest houseplant soil tend to congregate in bright windows or under lamps. According to "The Complete Houseplant Survival Manual" by Barbara Pleasant, the gnats that commonly infest houseplants are called fungus gnats.
Overwatering indoor plants contributes greatly to the likelihood of houseplant gnats. Gnats on indoor plants often enter a house by stowing away improperly sanitized soil or by sneaking through an open door or window. When a plant is outside in the warmer months, it is at risk of picking up houseplant gnats that are then brought indoors.
Drying out overwatered soil can be a simple way to treat a houseplant gnat infestation for most indoor plants. Some water-dependent plants require constantly moist soil and cannot be dried out without damaging the roots.
Gnat infestations in houseplants can be controlled by placing sticky gnat traps around to catch gnats and control the rate at which they breed. Sticky gnat-catching traps work best when placed near a lamp or any source of light that attracts the gnats.
Larvae are a form of baby gnats that hatch from the gnats' eggs. "The Complete Houseplant Survival Manual" suggests trapping the gnat larvae by placing some slices of raw potato in the soil. The raw potato is a friendly place for gnats to lay eggs. Periodically changing the slices of potato will remove much of the gnat larvae from the soil.
A severe gnat infestation can cause a plant to lose leaves and flowers, and can kill some of the more delicate houseplants.