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Little black flies on my indoor plants #817063

Asked November 30, 2022, 9:52 AM EST

Hello Fine Folks, Every winter I move some of my potted herbs indoors and each winter I get a huge number of these little black flies (like fruit flies). I started spraying the herbs with NEEM oil, but it doesn't seem to be working. Please help!! Thank you, Scott

Boulder County Colorado

Expert Response

Hi Scott, 
   I think what you have are probably Fungus Gnats. I am sending you a couple links to help you deal with them. I have had some success with the yellow sticky traps. Keeping the soil dry is also helpful. I have not tried the potato suggestion, but that does sound like a logical solution.
   It is a problem that takes some persistence to cure. 
The plants were probably infected outside and became worse when moved inside.  If the problem is severe enough you may want to treat with an insecticide containing a pyrethroid  or imidacloprid as suggested in the links. You will have to check the ingredients contained in the product you choose. The larvae are  more difficult to kill than the adults. 
   One other suggestion, if you have other houseplants, I would suggest moving them an isolated area, so they don't become infected.  Hope this is helpful to you, The Boulder County Master Gardeners

Fungus Gnats:
https://planttalk.colostate.edu/topics/insects-diseases/1445-fungus-gnats/

http://www.wci.colostate.edu/Assets/pdf/CIIFactSheets/Fungus.gnats.pdf
Boulder County Master Gardener Replied November 30, 2022, 6:53 PM EST

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