Fungus Gnat (Mycetophila fungorum)

Order: Diptera (DIP-ter-a) (Info)
Family: Mycetophilidae
Genus: Mycetophila
Species: fungorum

Regional

This bug has been reportedly found in the following regions:

Dewey, Arizona
Fort Bragg, California
Deland, Florida
Mary Esther, Florida
Sarasota, Florida
Vandalia, Illinois
Columbia, Missouri
Saint Joseph, Missouri
Dayton, Nevada
Spring, Texas
Glen Allen, Virginia
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Members' Notes:

0
positives
0
neutrals
1
negative
RatingContent
Negative

On Jun 4, 2009, LineyLou from Sarasota, FL wrote:

These things can be incredibly destructive; I grow rare & heirloom fragrant plants & watched helplessly while the larvae selectively slagged my most irreplaceable plants. I had applied predatory nematodes as a preventative ; since I did not lose everything, they may have helped. I applied a BT drench yesterday,& am applying a diatomaceous earth barrier today;then I will spray Neem oil everywhere,(& pray).
I was told predatory mites(Hypoaspis sp.??) were better than nematodes at fungus gnat control,& will try that too. Can anyone tell me how much diatomacous earth I need to mix into my potting soil to make it hostile to gnat larvae?? Not just as a barrier; I'd like to incorporate enough into the soil to permanently check any future invasions.