Not quite true when using Serenade...Serenade is actually a bacteria which eats/ feeds on powdery mildew, botryitus, mold, fungus etc...In fact, one method of serenade application is to water the plant w/ serenade solution (concentrate w/ water, of course) when young, in which case the bacteria (which is harmless to humans, by the way) becomes systemic as powdery mildew can and will absolutely wipe out the powdery mildew if it tries to surface again. A little prevention in early stages of plant growth does wonders...I saw all this demonstrated (watering plants w/ serenade solution to make it systemic) in a online video presented by the manufacturer. This will also protect your plants from a number of variety's of root fungus; besides powdery mildew, mosaic fungus & botryitus, etc.
Awesome shit (serenade). Well worth the $20 for a bottle of concentrate. Yah, it smells like shit when you spray it, but that goes away in about a week. I have not noticed any difference in taste of smoke or plant either (unlike Neem based products.)