Looper caterpillars invaded our tomatoes. This is an act of war, and so I needed a way to disperse toxic dust particles (Derris Dust) amongst the plants in a thorough and pervasive manner - though I should imagine the same technique could be used to fog with any dry powder. It certainly beats heck out of the little pepperpot holes on the end of the derris tub. Here's a shot of it being tested; it's more impressive when a lot of powder is used and great billowing clouds come out.
Derris dust is organic, but so is hemlock so only use it when no cold-blooded things you want to see alive are around, mask up, and don't muck about with it. Testing of the fogger was done with plain flour.