i have powdery mildew, and it was reccomended that sulfur burners were the best way to get rid of it naturally and it also works for pest control. the reason i have to use it in the dark is a mystery to me, thats just what it said in the instructions. my question about the light timing was that switching from 24/0 to 18/6 to 12/12 all in the same week is going to effect my plants.