I use a product called Sticky Sticks for any problem with gnats . It is a little piece of sticky yellow paper on a stick you place in your pot to catch any flying insects . When I water my plants I usually dunk them to give them a good drink . If I notice them in the bark , I use a couple of drops of cinamon extract to cut down on them . Seems to work .

I use Sundews and Butterwort plants , no fungus knats , you could try pouring diluted Physan thru the pot that works on ants so might work on knats ? Gin

I use a product called "Gnatrol" that I found on line two years ago this has worked for me and it is safe.
The active ingredient is (Bacillus thuringienses).
Good Luck

I have a Sundew plant that does a great job of keeping gnats under control. However, it doesn't like the dry atmosphere of a home. I am quite sure that it would like a greenhouse. Carol

Gnats
 

You may also purchase at your local garden center Ladybugs. They just love gnats.

Gnatrol has worked for me in the past along with the yellow sticky things. Since you started your post by stating you had just repotted your chids it would be hard to believe the medium was decomposing. Best of luck!

I use home made sticky traps made from a plastic bottle into which I have inserted a light . The bottle is coated with a sticky substance called Vastrap the light is connected to a timer switch which activates for three hours every night . It catches all the flying insects in my GH. The result is I have had more undamaged flower spikes on my Cymbidiums this year than ever before . I have also been able to cut down on the use of poisons .

Yes - I always read that it may mean your mix is breaking down and you need to repot - but all of my plants had been repotted very recently. So nix that.

Also have read it means you are keeping plants too wet - well some plants need to me constantly moist! When I tried to let the most problematic plants dry out a bit more I lost a spike on an angraecum - which btw is potted in charcoal, and two milts just became very sorry looking with tons of pleated foliage!
Also the first plant i found gnat larvae in was a laellia which 1. was only in that pot and media for maybe 2 months. and 2. was allowed to dry completely before getting watered! (and in a clay pot btw)

I believe I have addressed the problem - kill larvae in pot so they can't become adults and reproduce - and
trying to keep the adult population down - and out of the media by using repellant essential oils - so they wont lay eggs in pot and reproduce!
Spiders have helped with adults - and sticky traps etc all work toward this end!

All suggestions here sound good - and I will proly be adding to my aresenal as needed :)

I also had a previous battle with fungus gnats :(( I read that they live in decomposing matter, but they were in all my pots including the ones that were recently repotted, so I have to agree that I question them only living in decomposing matter. Anyway, I successfully used Bacillus thuringiensis (Bt/H-14) which is supposedly safe, but it does have to be used several times in a row to kill all the larvae because of the gnat's life cycle; a good source for the product and fungus gnat info is: Knock-Out Gnats™ Granules I also had the yellow sticky tabs from safer soap, they keep the populations down but they don't get all the gnats. Some of the research I did claimed they just live in the medium and don't do any damage to plants, but I don't think that is the case. After I got rid of them all my orchids looked better, and my Christmas cactus that was on its way out miraculously recovered :lol:

Wow! I didn't think my question would generate so much discussion! Thanks to everyone for responding!!

After reading everything, I think I'll try a one-two punch of the sticky tape and the Bt...which now that I think of it, brings on another question. I soak my plants when I water. If I mix some of the Bt into the soak water and then do a soak will that hurt the plants, or should I do a quick dunk and then soak in fresh water/fertilizer? Or is it better to do a sprinkle type application of the Bt. As I think I mentioned before, all my chids are in clay pots.

Who knew there was so much to this obsession! :)