Naw.. use if you have to.. its your crop. I'm suggesting people minimize e20 usage, Is e20 necessary to or as a preventative measure for growing is more or less what I'm saying, given the questionable outcome of e20. I think your application of e20 is correct applying it to a mother, that eventually will have little residual given the half life and the eventual quadrupling of mass of a flowered cutting. But who is say other growers are using it correctly?.. How late is too late for application for cannabis?.
I would freak the fuck out if somebody said, "I apply E20 every week just in case".. I would NOT smoke that.
I'm ok with somebody saying "I treated these clones once in quarantine with eagle," .. I'm ok with that.
If there's a legitimate need for e20, I get it.. I"m sure theres some environments like outdoors or whatever you have to bring out some big guns to fight PM. I'm guessing here but the risk seems low in comparison to some of the carcinogens or even the radioactive shit I have to deal with.. But Id rather avoid it.