I use Thuricide, it's also a BT product, but it's liquid and is mixed with water. Your powder is meant to be puffed onto the plants straight, but with a very light coating. You might find that Diatomaceous Earth (DE) would work as well.
The biological pesticide Bacillus thuringiensis is a beneficial bacteria applied as a spray to kill caterpillars. Sold under a variety of names such as Thuricide, Dipel, Bio-Worm, and others. Use Bacillus thuringiensis 'Israelensis' (Bti) in water for the control of mosquito larvae. Use Garrett Juice with Bt for extra benefit. Molasses at 1-2 oz. per gallon of spray also helps. It provides protein and keeps insect-killing bacteria alive on the foliage longer- even during rain. Bt 'San Diego' is good for Colorado potato beetle, elm leaf beetle, and other leaf-chewing beetles.
Garrett Juice is a commercial bottled form of his compost tea recipe. All of those recipes and information about products are available in the Dirt Doctor library.
This stuff is effective, particularly on caterpillars and bugs that were caterpillars, but don't spray it indiscriminately because, as you can guess, it will kill butterflies.
Dipel information at a garden center site. The sprayer might not spread as far as the dust, if that is what pdq is worried about. I have a puffer for the DE that would work for the dipel also. This is a much better choice than things that say they're natural but have pyrethroids (really toxic to everything).