BT isn't a chemical, it's a bacillus. Perfectly safe for humans and animals. I put the tabs in our ponds to get rid of mosquito larvae. No danger to the fish, plants, dogs or other animals that drink/live in the pond.
Tally HO!

What about the gnats us it a danger to them? I hope so. Thanks for the assurance.

I've been using a mosquito dunk in the watering can, since I am still using peat-based potting mix and had lots of gnats this fall after I brought some tender perennials indoors. It works. :-) Make sure to get the israelensis strain of Bt, also called Bti. There's another strain of Bt used for caterpillars which does not work on fungus gnats. I simply keep the dunk in the watering can and keep the can filled with water. I let the water sit at least overnight before I use it. All of my houseplants get watered with this solution, every time they need water. Bti only affects the larval stage of the gnats, so you will see adults hanging around for a while.

Fungus gnats are entirely capable of crawling into drain holes and laying eggs in the bottom of flower pots, so letting the top dry out a bit is not going to solve the problem. :-( I tried that too. Another option is to switch potting media entirely and use Al Tapla's mix; ask Jodi K about that, it works great for her. It took me until this month to find a place that stocks Pro-Mix, so finding ingredients for Al's mix where I live is like a long-term scavenger hunt. I get blank looks anytime I ask about any of the ingredients.

Edie

Here is a link that might be useful: EPA fact sheet on Bti

Nematodes are awesome. I use Gnatrol... dissolve it into my spayer/pressurized waterer the day before and apply it to all the plants and I do this every week or so to keep the population under control.

I found that changing from regular potting mix to Al's gritty, fast draining mix almost completely eliminated my gnat population last year. It stays drier, leaving very little moisture for them.

bama gardener,

This is the first I am hearing about al's gritty mix. Does that seem to work well for Hippis? I usually add a good amount of expanded shale and perlite to all my mixes, but this year it seems like the just dont care. I might have to give a new mix a try.

Jason i think if you do a search for Jody's explanation of potting medium you will find all you need to know about this gritty mix. Some people don't care for it-- others love it-- again it all depends on your conditions and culture of your plants. Everything I plant that doesn't go into hydroton goes into a very fast draining mix that is essentially the consistency of cactus mix (and not the stuff you get from miracle grow etc as it has too much peat)-- but very airy volcanic parts with lots of perlite etc. I do this because my climate has very low humidity and this fast evaporation causes uneven drying-- having a fast draining "gritty" mix helps a lot with that problem. I have to water more often but the plants are happier for it.

DR