Fungus gnats in and of themselves aren't particularly harmful to plants, but can act as a vector for disease.
Hang a no-pest strip, and make sure that your grow room has nowhere for standing water to sit and stagnate- that's where the nasty little shits hang out and do their bug thing.
Pyrethrin bomb the room if you want faster and better results, and repeat once about 3 days after the first bomb, to kill any flies that emerged from a more protected life stage, such as eggs, and missed the first round.
stinkyattic Reviewed by stinkyattic on . Little flies on coco Using coco with run to waste. Have noticed these small flies that seem to run round the rims of the pots. Put up sticky pads and caught quite a few around the ceiling. Looked at them with a glass and they are small and black with wings, long and thin about 1mm long. Cant notice any damage on leaves or anything much underneath. Had them for a few months now. Been offered soem systemic spray that is pretty nasty stuff that will do the job but am in 4th week of flower so am reluctant to spray Rating: 5