Just as a note to your reply Stinky, I work for a university under the wing of someone who has been caring for a large number of tropical plants, which I consider to be much more finiky than cannabis, for 25 years. She has been using this dillution of alcohol and water with success that entire time and has not noticed any ill effects from its use. The decision to use alcohol dillutions was made by a board of professors in the botany field, who oversee our work. As per their recommendation, we spray twice a week, liberly, and this keeps most common pests in check. And from what I have seen, the only thing that will remove the protective covering from the leaves is by rubbing it off, with your hand, rag, etc, while cleaning.

Just thought I would clarify a little, although I could see how going overboard with this could be potentially harmful. I am not exactlly sure if the effects are different on cannbis, but I personally use this method on my plants and houseplants, and have not noticed any ill effects.