When I start seeds indoors, I have usually used a mixture of hanging basket mix, peat moss and perlite or vermiculite. It has worked well, but last year I got fungus gnats that I simply could not control - even though I made the top 1/4" solid perlite, and hung all sorts of pest-control strips, and sprayed regularly with fungus gnat spray - and in addition some fungus got into the mixture with disasterous results. So this year I am using pure soilless mixture - for those in this area, it is Mica Mix. I had hoped that the seeds contained enough nutrients for some significant growth, but one kniphofia reached 4" and when I accidentally moved it, it came right out of the soil - with no visible root - and so I fear that it must be transplanted at two weeks of age. Presumably that is or will be true of the other seedlings too. This will mean that I will have pots of soil for the gnats, and the benefits of the mixture will be lost. Plus the labor will be ghastly: I can plant 50 seeds in 5 minutes but I expect that transplanting them will take hours. Finally, I would expect a 99% mortality rate as I transplanted them. So here are my questions: 1. Does anyone have any successful ways of eliminating fungus gnats if I go back to using soil? 2. If I continue with my current process, will I really have to transplant soon after the seedlings emerge? If so, what is a good web site showing exactly how to transplant them without harm (I am rather weary of websites: I have been to dozens of how-to-prune-your-grapevine sites but none of them shows a vine that branches like mine do and so they are all useless to me; when I try to find out germination processes for different seeds I get sites that tell me anything from 15 C to 25 C temp, from do-not-cover to plant-1/2"-deep, from cold-stratify to plant-like-usual, from takes-one-week to takes-three-months, all for the same seeds...).
Incidentally the gnats may be thriving in other potting mediums throughout your home.... spray with an insecticidal to the soil surfaces which may help eliminate your problem...
If you have fungus gnats you have to kill the larva as well as the adult.I use a product called gnatrol.It's a biological larvicide.It works well.I also hang the long sticky fly strips to catch the adults.You have to treat EVERY pot that has dirt in it to make sure you get them all.
I am sure that my gnats do not inhabit any other dirt areas, since (a) my germinating area is in my workshop, closed off from the rest of the basement by a pretty good door, and in any event there are no other plants in the basement and (b) I have never seen any flying thing anywhere but by the germinating area. I hung the yellow strips everywhere, and they got a fraction of the flying gnats, but a very small fraction. I will look into the product that you mention - have never seen it in a store. I have also read that rubbing alcohol will kill them, but I suspect that I'd need many litres - since the soil would absorb much of it - to do all my soil, at an enormous cost.
sd- you might try this stuff on a couple of the most urgent and see how it does- it seems at the least, very un-bug-friendly... http://www.botanicalgarden.ubc.ca/forums/showthread.php?t=47998
The larval stage of the fungus gnat lives in the soil and feeds on the roots of your plants.If you have adult Fungus Gnats you have larva in the soil,you just cant see them.The could have come in a bag of potting soil or a new plant. http://ohioline.osu.edu/hyg-fact/2000/2114.htmlMaybe this will help.