Eric, what you're referring to is Bt. var. Israeliensis. We use it here in Canada for mosquito control. The bacteria attack many species of mosquito larva and is quite harmless to people, animals and the environment.
The main method of prevention for fungus gnats is to keep the upper surface layer of the potting media on the dry side. Fungus gnats mainly feed on decaying matter, as Iris stated, but will sometimes nibble on root tips. Usually more of a nuisance than anything, and yes, they LOVE rockwool!! <There is an organic means of effectively controlling fungus gnats. It is a form of Bt that used to be called Gnatrol...It now goes by a different trade name. It smells and looks like malted milk....and has become very expensive. I do not know of any UK sources, but it used to be available in the US from Garden's Alive. It is effective, if given in at least 3 weekly doses...but bactericides such as RD-20 or Physan will of course negate its effects. Another, less effective solution is to spray the compost surfaces with pyrethrin. While annoying, I have never found fungus gnats to be really damaging....but they can also be found in inorganic mixes. In fact, my brief (very brief....) foray into using rockwool produced the worst infestations I have ever had. Of course, they were supported by the organic slime that grew all over the inorganic medium.> Cody Cruise Valley Pest Consulting _______________________________________________ the OrchidGuide Digest (OGD) [EMAIL PROTECTED] http://lists.orchidguide.com/mailman/listinfo/orchids
