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Re: fungus knats
Flies in general like the conditions that favor a little alcohol production. When the soil gets too waterlogged, you get anaerobic conditions, and thus production of the stinky, smelly compounds that flies like.
A select set of fungi grow just on the soil surface, because the soil is too wet for them to grow into the soil. The normal consumers of the fungal biomass are drowned in the waterloggged soil.
Fungus gnats are attracted to those particular fungi on the soil surface, and to the smelly compounds the bacteria in the waterlogged conditions produce. They lay eggs, and you have a flush of gnats every 10 to 14 days. Often, you apply the pesticide, exit the adults, but then the next generation of fly eggs hatch.
What to do? You have to keep the soil moist enough for the plants, but then you have gnats.
The real take-home message is that you don't have good soil structure. When you apply water, it should drain into the soil, not get held up on the soil surface. You need to keep the air passageways into the substrate open so the competitors of the fungus gnats don't drown.
One simple way to deal with some of this, is to apply a GOOD, aerobic compost, and mix it into the surface of the soil, then put a light layer of crushed egg shell, or vermiculite, or outher powdery material in the soil surface to maintain moisture in the soil, but keep the surface fungi and smells from attracting the gnats.
Maintaining moisture is necessary while the diverse set of fungi you added in the compost - or compost tea - does it's job of building soil strucutre, making air passageways, etc.
Once someone gave me a sample of "compost" to put on my soil, and I put it on the surface of a pot with a favorite orchid of mine. It was compost, right? Wrong. It had poor structure, and I got an out-break of gnats like you don't want to know about! Which tells me the compost wasn't compost. It looked good, because it had been sieved, but big mistake. I'm still fighting to get that soil back to the good place it was.
Why can really good soil get messed up with just a little addition of bad stuff on the surface like that? I don't know. Or maybe my soil in that pot wasn't as happy as I thought it was. I hadn't put commpost tea on it for about 9 months...... Duh.
OK, but good compost tea. I know people putting SoilSoup on their plants and they still have fungus gnats. What does that tell you about the SoilSoup?
Elaine Ingham
President, Soil Foodweb Inc.
Corvallis, OR
Port Jefferson, NY
Lismore, NSW, Australia
Hilversum, The Netherlands
www.soilfoodweb.com
.