Fungus gnats are veryÂ small flies (3mm) that look like tiny mosquitoes. They are grey or black, have very long legs and a pair of see thru wings.Â
Adult Fungus Gnat (left)-Insect Control Branch, Winnepeg, Manitoba Canada, Fungas Gnat on a yellow sticky trap (right)-University of Florida
Larvae are extremely tiny and are very hard to see. They are whitish to greyish with black heads. Handpicking is a tough job.
Larva (left), Eggs (right)-Minnesota Deptartment of Agriculture
Lifecycle-Rutgers Cooperative Extension
Habitat and Lifecycle
They are found worldwide and they are mostly pests of your houseplants, potted plants outdoors, greenhouses & bedding plants. They love moist highly organic soils. Larvae live in the soil and adults live just above soil line. When watering you will know if you have them as they fly about madly. In the house they are found all year long and mostly in the fall outdoors.They have a continuous lifecycle completed in about 2 weeks so control is extremely hard.
Damage-University of Florida
Diet and Damage
Larvae are more apt to damage the roots of your plants if they haven’t got enough moisture. They are found anywhere in moist, highly organic soils. They can cause major damage to small seedlings causing them to wilt and die from lack of roots. They can also spread disease.
1) Dry Out Your Soil
Whenever possible let your soil dry out for a few days, the larvae will die from lack of moisture.
2) Bt & Bti
Follow directions on the label. Bt only works for a few days and then reapplication is needed.
3) Yellow Sticky Traps
Place sticky traps near the plants affected and then water the soil…..the adults will fly up and be trapped.
4) Quarantine New Plants
If you buy plants from a nursery you can cover it with a fine mesh for a few days to make sure that you haven’t bought a plant that has larvae.
5) Parasitic Wasps
There are many of these types that lay their eggs in the worm and this becomes food for the baby wasp.