Identification of fungus gnats
Fungus gnats (right) are small
(~1/8"), dark, primitive* flies that often plague
potted houseplants in homes, greenhouses, and
commercial mushroom growers. Fungus gnat larvae live
in soil where they feed on soil fungi and plant
roots. Full grown fungus gnat larvae are about 1/4"
long and have a very distinct, dark head capsule
Fungus gnat larvae damage plant roots
Adult flies can be a nuisance when
present in high numbers but the damaging stage
is the larvae that feed on plant roots.
Fungus gnat larvae can do significant damage to young
plants that don't yet have a developed root
system. They are most often a problem in greenhouses
and potted house plants.
Fungus gnats may have many generations
per year so populations can build quickly under
favorable, warm conditions. The best, and safest,
way to mange fungus gnat damage is to monitor for
adult flies using yellow-colored sticky traps and if
an infestation is found you can treat soil with entomopathogenic
nematodes (see below for details).
* Primitive flies include gnats,
midges and mosquitoes. These are generally small
(except crane flies), delicate flies with long
antennae. The "higher" flies, like house flies, have
short antennae and tend to be larger and more