Identification: Adult fungus gnats are delicate in appearance. Often they can be seen running across or flying near the soil surface. They are weak flyers and are attracted to light.
The larvae are small worm-like creatures up to 1cm long with shiny black heads . If you look closely at the top of the soil you may notice tiny (almost transparent) larvae. It’s hard to spot them, though, as they tend to exist mostly under the soil.
Damage: The larvae generally feed on decaying organic material or fungi growing in the soil. The larvae of some species will also feed on roots. This feeding is especially damaging to very young plants. With older, established plants, the initial sign of an infestation is that the plant loses its normal healthy appearance.
Dry conditions- take soils out and let them almost dry out (until first signs of plant withering) and plug them in the garden again. Dry conditions will kill the larvae. It might be necessary to repeat the procedure couple of times to
Yellow sticky paper- helps to monitor and keep down the number of fungus gnat adults but it does not solve the issue entirely.
Hydrogen peroxide- mix one part of hydrogen peroxide (3%) with four parts of water and add it to the tops of all the soils. Be careful not to burn young plant roots with a mixture that’s too strong! It can also be added to a water tank to prevent mosquitoes.
Biological control- Hypoaspis miles are fungus gnat larvae natural enemies