PlantLife Online

Answer

The gnat like insects on your plant are most likely "fungus gnats" which are common outdoors and often find there way indoors on houseplants. Fungus gnats (Bradysia species) are small, dark colored flies that spend their time on and around the soil surface. Adult gnats are often found congregating around the rim of pots. Adults only live for a few days and lay eggs in soil cracks and around the base of plants. Fungus gnat larvae feed primarily on decaying plant materials in the potting soil, changing soil moisture conditions is the first step to control the population. Watering should be limited so that the soil surface can dry between waterings. Adults can also be suppressed with the use of sprays of pyrethrins and pyrethroid insecticides which need to be applied often to be effective. Because adult fungus gnats have such a short life controlling the larva is most important. The biological insecticide Bacillus thuringiensis var. israelensis or neem oil labeled for soil drench use are highly effective. If the infestation is mild changing the watering schedule and spraying the adults with a pyrethrin could be enough to control the population. Soil drenches maybe difficult to find, if your local garden center does not carry these products they can be found online.