Treatment
Open up webs as soon as you see them hanging in trees. Use a long stick or a pressurized stream of water to reach them. Wasps will take care of them. (This is one very good reason for not killing wasps.) This method works extremely well, is very easy, and harms nothing but the targeted pests.

Caution: Do not try to reach them with a burning torch – it is too dangerous. Most municipal areas have ordinances against burning yard waste.