Hugh if your buddy has hibiscus in his yard then spray them or remove them. My parents had some infested bad years ago and they made their way to my grow via me. For some reason the hibiscus seem prone to whiteflies Ive seen it several times in several places. They get so bad the plant looks greyish white. On a positive note this "yankee weather" might knock them and the spidermutes back....for a bit
I have one hibiscus near my grow and I use it as the indicator. When I see any pests on it, I know it's time to get serious as it's just a matter of time until the pests find the cannabis. Weird how it always seems to be the hibiscus first, but it's been that way for me for years.
You guys up north may have had some benefit from the "yankee weather" but here it just got cold enough to make me close the windows and break out a light blanket. Probably be the last cool weather here for the next 8 months or so.