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Need to apply Bt for fungus gnats but plants don't need water!

Posted by Rick7072 6b (My Page) on
Sun, Nov 25, 12 at 6:24

I have a fungus gnat problem with my indoor herb plants and would like to apply Bacillus thuringiensis. So yesterday I bought six Mosquito Dunks and last night I cut off about 1/3 of one and put it into my 2-gallon watering to soak overnight as I've read that's good practice.

Yet my plants don't really need watering right now, and I know that over-watering provides a perfect environment for fungus gnats!

So...should I water anyway, with the understanding that this particular watering with Bt-soaked water will be helpful against the gnats? Or should I wait until the plants really need water? I'm hesitant to wait because I've been seeing the gnats for two weeks already (it took a while for what was happening to sink in!) and I know infestations can get really bad quickly.

Any advice would be appreciated.


Follow-Up Postings:

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RE: Need to apply Bt for fungus gnats but plants don't need water

I would not water with the BT. Fungus gnats are symptomatic of too much moisture. Allowing the medium to dry out, disturbing the surface (just stir it a bit with a table fork, and adding a little fresh medium to the surface will fix them. There's really no need for BT at all if the watering is sorted out.


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RE: Need to apply Bt for fungus gnats but plants don't need water

Bt should only be applied when your plants needs to be watered. A highly porous potting mix is much more forgiving than the typical potting soil.

Flora 's advice is good, though I'd incorporate perlite rather than more potting soil.


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RE: Need to apply Bt for fungus gnats but plants don't need water

I got fungus gnats one year from a bag of organic potting soil. No matter how carefully I watered, it did not help get rid of the gnats! I used the Bt dunks when I watered, still had them. I read to sprinkle cinnamon liberally on the soil surface. It took a week or so, but that did the trick.


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RE: Need to apply Bt for fungus gnats but plants don't need water

I've heard about using cinnamon and will try it. Is it well-known as an insecticide? Is it targeted specifically to fungus gnats or is it a general insecticide? How does it work? I think I'll do a little internet research. Thanks.


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RE: Need to apply Bt for fungus gnats but plants don't need water

Cinnamon doesn't work either. Put a glass of vinegar near your plants and the fungus gnats will disappear. If the vinegar evaporates, rinse the glass out and refill it.


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RE: Need to apply Bt for fungus gnats but plants don't need water

  • Posted by gjcore 5 South Aurora Co. (My Page) on
    Thu, Jan 10, 13 at 21:31

I find that neem oil spray works pretty good for fungus gnats. Might take a couple times through to get rid of them.


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RE: Need to apply Bt for fungus gnats but plants don't need water

Thanks, since I posted that message I've been using neem oil and it does seem to be working pretty well.


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