While the small size of the gnat can make it appear less serious as a pest, it is important to remember that gnats reproduce quickly and populate infested areas in swarms. This is how gnats become larger problems to homeowners or apartment residents.
Fungus Gnats in House PlantsFungus gnats lay their eggs in damp soil of plants that have been overwatered. When the eggs hatch, the immature gnats feed on decomposing, organic material in the soil. These gnats are attracted to fungus that grows in the soil of houseplants that have been overwatered.
Roots are commonly affected in areas infested by these gnats. Gnats feed on the roots and root hairs of plants, as well. They are most harmful to small plants, but can also destroy large plants if the plant is already unhealthy or if the gnat population is extremely large.
Growers go to great lengths to prevent and eliminate gnat populations, as the damage caused by a gnat infestation can damage both ornamental and edible plants.