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Shop > Beneficial Insects > Fungus Gnat Controls

The damp, moist environment in greenhouses favor both fungus gnats and shoreflies. Fungus gnat larvae are translucent, white and legless, about 1/4 inch long when mature and have a shiny black head. The mosquito-like adult is about 1/8 inch long with long legs, a pair of clear wings and long antennae. Fungus gnats are weak fliers and are frequently observed resting on pot media or running over the foliage or other surfaces. The larvae feed on fungi and decaying organic matter and often injure seedlings and plants. Larva feeding occurs on young, tender roots and in the stem at the base of the plant. This feeding injury provides an entry for disease pathogens. A female fungus gnat may lay up to 300 whitish eggs in clusters of 20 or more. The eggs are deposited on the surface or in the crevices of moist soil or potting media. Eggs hatch in about six days. Larvae feed for 12 to 14 days before changing into pupae. The papal stage may last five to six days. Adults live up to ten days. The life cycle from egg to adult requires approximately four weeks depending on greenhouse temperatures.

Shore flies also occur in greenhouses and are often confused with fungus gnats. The adult shore fly is about 1/8 inch long and has a robust body, very short antennae, shorter legs and dark wings with about five light spots. Larvae are off-white and do not have distinct head capsules. Shore flies do not injure plants through direct feeding, but can carry root rot pathogens from diseased to healthy plants.

Fungus Gnats and Shoreflies Damage:

  • The larvae feed on fungi and decaying organic matter, and often injure seedlings and plants.
  • Larval feed damage can provide an entry point for disease pathogens such as damping-off.

Beneficial Insects and Tips

  • Stratiolaelaps scimitus (formerly Hypoaspis miles) and Gaeolaelaps gillespiei lives and feeds in the soil on both fungus gnat larva and thrip pupae.
  • Dalotia coriaria (Rove Beetles) lives on fungal mates and feeds on shore fly larvae and eggs.
  • Nems beneficial nematodes, kill fungus gnat and shore fly larvae and thrip pupae.

Monitoring Tools:

  • Adult flies can be monitored with yellow sticky cards placed at the base of the plant at the soil line. The cards should be spaced at 1-4 per 93m2 (1,000 ft2) in the growing area. Place yellow cards in a horizontal position just above the soil surface or lay them on the top of the pots.
  • Larvae can be monitored using raw potato chunks with the peel removed and placed on the soil surface. Larvae are attracted to the potato chunks under which they move and congregate. Check the potato chunks daily for larvae. Potato disks cut one inch in diameter and 1.3 to 2.5 cm ( 0.5 to 1 in) thick work well. Ten potato disks may be sufficient to monitor a 929 m2 (10,000 ft2) greenhouse.
The key to success in controlling fungus gnats is PREVENTION.



<b>GAEOLAELAPS GILLESPIEI</b><br> (Predator)-Available in fall 2018
(Predator)-Available in fall 2018

<b>BENEFICIAL NEMATODES (NEMS)</b><br>  (Soil Larva Parasite)
(Soil Larva Parasite)

Natural Insect Control