Fruit flies and fungus gnats

I agree with Marni about Gnatrol. When you apply it to the soil it introduces a natural bacteria that inhibits the growth of the fungus gnat larvae and breaks the life cycle. I used it for ten years when I was a nursery grower and I still use it at home on all my orchids. Good luck!

 

The particular bacterium, Bacillus thuringiensis v. israelensis, is actually toxic to the larvae. Many find that putting a "Mosquito Dunk" in a gallon of water for a few days provides plenty of bacteria.

The only issue I have with BT and sticky traps is,it seemed to me, that you're treating a symptom, rather than the problem.

Fungus gnat larvae feed on fungus that is growing on decomposing organic matter - your potting medium. Treating the gnats may get rid of an annoyance, but you're still risking your plants...

 

This fall, I used Talstar as a soil drench and spray when I brought my plants inside. Seems to have been pretty effective on the fungus gnat and sow bugs that usually come in from the cold.

 

Agreed with Ray. I used the Mosquito Dunks product in a gallon of water. Problem was cleared up in a couple of weeks, and they haven't returned. RePotme.com has them, but I found them at my local Home Depot.

 

I have them too (at a considerably lower price), but if you can get them locally, do!

 

I have used the predatory nematodes treatment with success. You can get it on Amazon. I forget the brand name.

 

Get a praying mantis !!

 

If you have a gnat problem, like ray said there is a problem with your medium or plant tissue (roots and stem) maybe decomposing. If you are not into using pesticides, especially in your home (Talstar is labeled for use in greenhouses,but I believe has a 8 hour reenter time and I don't know if I would use it in my home) another way would be to use dish soap (Dawn) at 1 table spoon per quart (32 oz.) use in spray bottle and spray all parts of the plant including the undersides of leaves. You can also use this as a soil drench for the medium. You will have to do this every 5 to 7 days until you stop seeing gnats. This method is also good at getting rid of aphids. But as said before this is only solving the symptom not the problem.

 

Would cinnamon stop the fungus from growing or effect the decomposing?

 

If you used cinnamon powder, you'd desiccate the root system. If you found a way to treat with a liquid extract, it may kill the fungus, but would only do little-, and only temporary slowing of the decomposition going on.

The bottom line is...repot.