I had to use copper oil fungicide this grow to combat septoria. Everything I read says OK to apply up to and including day of harvest. They even suggest spraying it on harvested fruits to preserve them. I cannot find if the residue left on buds is safe to smoke/vape or ingest. I've been reticent to wash off buds after harvest and don't wet them at all during the last weeks. I know THC/CBD are not water soluble but some tricomes are no doubt washed off with the action of spraying, so I have not. Yet I'm reticent to smoke something that has a little trace of blue residue on it.