Ugh! Please help me get rid of "gnats" on plants and soil.

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nephifofum Olympia, WA Oct 08, 2012

For weeks, I have battling these small, flying bugs that I tend to think of as gnats or fruit flies. They are so quick and so tiny that it's almost impossible to hit them with a swatter.

Somewhere, I read that the mother lays her eggs in the wet topsoil. Today, I looked at the arugula I'm growing indoors and there had to be at least 50 of the things crawling around on the top of the dirt. They could not fly, so they must have been a new batch of "babies."

I have some insecticidal soap, but it says to wait 5 to 7 days between applications. I sprayed this morning and it didn't seem to kill any of them.

Isn't there something I could put in the water I use to water the plants that will soak right into the soil and kill them without harming my plants?

I would be forever grateful if someone could help me solve this problem!

Dave

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ecrane3 Dublin, CA(Zone 9a) Oct 08, 2012

They are probably fungus gnats, and typically when you have them it means you're watering your plants a bit too much (and the overwatering will be worse for your plants in the long run than the gnats). To get rid of the gnats, you can use yellow sticky traps for the adults, and buy some mosquito dunks (or other product with Bt in it) and add that when you water, that will take care of the larvae in the soil.

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purpleinopp Opp, AL(Zone 8b) Oct 09, 2012

If you can let the soil dry enough without wilting your lettuce too much, you may be able to get rid of them without buying anything or putting more products on something you intend to eat, I assume.

These things are especially attracted to peat from what I've seen of them. If you prefer a mix with peat in it, try to find something to make a non-peat layer on top, maybe 1/2" of perlite. I just eliminated peat from all of my pots, but this may be another way to make your planting an undesirable environment for fungus gnats if you like using peat.

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nephifofum Olympia, WA Oct 09, 2012

Quote from ecrane3 :
They are probably fungus gnats, and typically when you have them it means you're watering your plants a bit too much (and the overwatering will be worse for your plants in the long run than the gnats). To get rid of the gnats, you can use yellow sticky traps for the adults, and buy some mosquito dunks (or other product with Bt in it) and add that when you water, that will take care of the larvae in the soil.


Forgive my ignorance, but what is "Bt?"

Thank you both for your suggestions. I just can't believe how out of control these things have gotten.

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purpleinopp Opp, AL(Zone 8b) Oct 09, 2012

http://en.wikipedia.org/wiki/Bacillus_thuringiensis
Bacillus thuringiensis

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