Species of the family Sciaridae is referred to as a fungus gnat. These are predominantly species of the genera Sciara, Bradysia, Lycoria and Lycorelle. Like mosquitoes, they are also thread-horns (Nematocera) but, just like flies, they also systematically belong to Diptera. Determining individual species is difficult. Fungus gnats only have a pair of wings just like all thread-horns. The rear pair of wings has been converted into so-called ‘balancers’ (halteres). Fungus gnats are usually small and only measure a few millimetres in length. The body has a long shape and is a dark matt colour (hence the name). Their eyes are small and legs and feelers are long. They usually stick close to the surface of the earth. The larvae of fungus gnats develop in decaying plant parts and therefore can be found in the substrate of potted plants. The larvae are white with a black head and measure 1 to 2 mm in length. Eggs develop over three weeks into fully grown insects.
The larvae can also attack living plant material and therefore damage roots. Above all, seedlings and young plants are at risk of being eaten and can be affected by pathogens at the sites where they were eaten.
Flying gnats which hatch can become a nuisance in the case of mass reproduction.
Adhesive traps can be used to catch large quantities of fungus gnats and to therefore reduce the infestation to a tolerable level. Fungus gnats reproduce in particular with too much watering. Plants should therefore be kept as dry as possible.