Organic control of fungus gnats

gnat at gnat at
Thu Apr 3 21:39:02 EST 1997

P Okerholm wrote:
>         Now that I've survived the ravages of Winter (barely), I am
> looking forward to my next challenge. I have noticed that the fungus gnat
> population in my Shiitake growing facility is on the upswing. I'm
> certified organic so my control methods are limited. I tried beneficial
> insects last Fall with some success. I used a predatory mite called
> Hyoapsis miles. My only concern is that they may spread mold spores etc.
> as they roam around, just as the gnats do.
>         I may try parasitic nematodes like Steinernema carpocapsae. These
> mini worms may stay put while they do their thing.
>         I'd like to try a particular strain of Bt (Israelis?) which
> supposedly works on gnat larva but I don't have a source for it.
> Diatomaceous Earth is something else that may have some application.
>         Does anyone out there have experience with these, or other,
> organic methods of pest control? Any recommended sources?
>         BTW - My main source for most of this stuff is:
>                 The Green Spot
>                 Dept of Bio-Ingenuity
>                 93 Priest Rd.
>                 Nottingham, NH 03290-6204
>                 Phone   603 942 8925
>                 Fax       603 942 8932
>                 Email    GrnSpt at internetMCI.comI have controlled fungus gnats with bacillus thuringiensis serotype H-14.
This was obtained from Gardens Alive in I believe Cincinatti OH.
The maker is Abbot Labs Chemical & Agricultural Products Division
North Chicago IL 60064.
This method of control may give your mushrooms an off taste as the 
bacterial solution has a strong odor.
I have used nematodes to control fungus gnats but the nematodes need to 
be reapplied every few months the bacteria do not. One heavy application 
of bacteria was sufficient. 
I also use "sticky yellow bars" to trap adult fungus gnats.
These methods of control are effective only if the infestation has not 
reached high levels. I begin treatment as soon as fungus gnats appear.
Nematodes are not shipped during freezing weather.
So either bacteria or nematodes in combination with an adult gnat trap 
like "sticky yellow bars" would give you good control of this problem.

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