To clarify, Bacillus thuringiensis israelensis is used against Diptera larvae, most commonly mosquito larvae but also fungus gnat larvae. When mixed into the irrigation water for potted plants, one must continue using it for at least 3 weeks to disrupt the fungus gnat's life cycle. The form which kills caterpillars is different -- it's Bacillus thruingiensis kurstaki. Hope this helps, Jean in Portland, OR -----Original Message----- From: Kelly O'Neill <kellyo@wetrock.com> To: Pacific Bulb Society <pbs@lists.ibiblio.org> Sent: Sat, 28 Mar 2009 8:19 pm Subject: Re: [pbs] Fungus gnats-- was --Looking for pic of the smaller Narcissus fly > Let the surface of your pots dry out to prevent > infestation. There are multiple advantages to letting pot tops dry out. For the gnats though, I use a BT product (Bacillis thurgensis may be spelled wrong). Comes in small bottles at many retail garden stores. Takes time to build up the living anti-gnat population of BT critters. Then they attack the larva under the soil. Works great for me. Just dilute and pour on soil. Water it in a bit. Once they are established, just treat new soil or pots you bring in if you want them to be protected. The stuff probably kills all butterfly and moth larva. I'd be careful not to get it on the leaves of plants eaten by larva you love. May not be active outside the soil though. Happy "Spring" for those on the North part o' the planet, KellyO