Your potting media and its water retaining ability may be the big issue.

Meanwhile ....... got to HD or Lowes and buy a package of mosquito dunks. Throw a 1/4 of a doughnut dunk in a gallon jug and fill with the water you use to water your plants. Let sit overnight or a bit longer in a dark area (no reason to give algae a chance to grow). Shake well and water your plants with it. Refill jug and put away until the next watering. The dunk chunk in the jug will eventually completely disintegrate. Until then, leave it in the jug and keep reusing it. The bacteria in the dunk will kill off the gnat larvae.

NOTE: This is NOT and instant fix. It will take a week or two to wipe out the larvae.

It doesn't look like your research resulted in anything useful. Fungus gnat larvae, in potting soil, feed on peat moss particles, the slough from roots, and even tiny healthy roots. Using cinnamon or barley water would be useless.

The adults seek out moist (usually overly so), mucky potting mixes in which to lay their eggs. The larvae will thrive in those conditions. Providing a very porous medium is really all that is needed to prevent population from building up. My preferred mix consists mostly of pine bark fines....very little peat.....and I haven't seen a fungus gnat in many, many years.

Sometimes, just easing up on the watering frequency can help but that's not a sure thing unless something has been done to improve the consistency of the potting mix....from too fine and mucky to coarse and porous.

The other useful tool in fending off these little pests is a naturally occurring bacterium, Bacillus thuringiensis israelensis, which kills the larvae once ingested. We are able to apply Bt as a product called Gnatrol or by dissolving ordinary mosquito dunks in your watering can.

Paul....your most excellent comments weren't there when I posted mine. :-)

I'll need to go on a quest for supplies now. I have almost wiped mine out (and almost changed completely to good soil, or Al's gritty mix), but every now and then one will find its way in front of the computer monitor.

Thanks for the help I wasn't really looking for!

Go buy a package of "Mosquito dunks" at the garden center. Put one quarter of one in your watering can. This will kill the larvae in the soil and stop future generations. Use sticky traps and manually kill the adults.

Thanks for all the help!
Ill be heading th store later today to get some of those dunks.
I cant however repot any my.plants untill spring as I have no where to do it and I cant do it outside.
Also I was looking at old threads about putting hot water in the soil.
Does this actually
work?
If so could I Put a mosquito dunk in with the hot water and double whammy them?
Thanks

DON'T use hot water. Room temperature of SLIGHTLY warm.

If you can't repot, at least reduce watering and stir up the surface of the medium with a table fork or stick. This will help it dry out and disturb the flies. Keep the surface scuffed up regularly.

â¢Posted by rhizo_1
Paul....your most excellent comments weren't there when I posted mine. :-)

I'm sneaky that way. heh