@Dr. Who Last year I had a hibiscus that became loaded with wooly white flies. Shaggy white "hairs" dangling from the undersides of the leaves, thousands would take flight if the plant was disturbed. Completely rid of them in a week.
That was outside of a grow, they never made it inside.
Earlier this month I noticed a single white fly in one of the veg rooms (different location). Spotted a few after "disturbing" the plants. Four days, 2 sprays (couldn't spray the day I noticed them, had to wait until the next "lights out"), gone. They must have come in on someone's clothes (during recent trimming or potting). Didn't find any elsewhere. Haven't ever seen them outside of that location.
On the hibiscus I used neem (Green Light), then Monterey's (spinosad), then "something special".
In the veg room it was Monterey's, then "something special".
Outdoors, in an area "infested" by them, I could see it being very difficult. As it stands, Whiteflies VS Aphids, I'll take the whiteflies.