yes it truely kills all kind of bugs and is safe for plants heres a word of warning about when you use it
http://www.pcl.ox.ac.uk/MSDS/DI/diatomaceous_earth.html if i rember right its made up of microscopic diatoms which literly cut insects to shreds. to use to wipe the lil buggers out just put it onto the medium about a half inch at most. i've used it for soil and works wanders as far as stunting plants i've never heard that before. also if i rember right ed rosenthal use to advocate it use so for me thats always been good enough to go on for me