Sorry...couldn't resist for some reason. I'm far from scientific about it, and probably as politically incorrect as one can get about applying pesticides. I do spray when the wind is calm, keep the kids and dog out if the area until everything is dry, and only spray trees that need it, but I don't use a mask or anything. Then, when I do find pests, I hit them hard, and every 7 days if I find mites, scale, or aphids, until they're gone. If I spray in the evening, I'll use the hose and wash down everything but the foliage the next day. Never had a problem, other than squirrels and birds falling dead out of the trees above, but nothing a good umbrella can't handle. ;-)