Does anyone have any suggestions for a drench for fungus gnats in begonias, kalanchoes and poinsettias? Now that endosulfan is off the market, I am looking for a different chemical to drench with

There are several effective chemicals that can be applied as a drench including Distance, Citation, and Talstar. These three are all labeled for Poinsettias. You will want to consult the label for the entire list of labeled crops. You can also consult our Poinsettia Federal Insect Control Chart (260K PDF) for a complete list of chemicals labeld for fungus gnat control.

Rae,
I would highly recommend using Steinernema feltiae from Koppert (Koppert. Since they are a nematode there are no REIs or reporting (not a pesticide) or phytotoxicity issues. If you use the high rates I have found them to be extremely effective which is backed up by an article in GPN
GPN article.

Doug