Organic control of fungus gnats

[P Okerholm]

        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.com