Hornets construct large grayish-brown carton like nests, many times hanging from a tree or bush. Treating for hornets as well as all other wasps should be done at night. Simply removing the wasp nest will not resolve the problem, because surviving wasps will reconstruct a new one. The best strategy is to treat the wasp nest at night when all the workers and queen are present.
Hornet nests have a single opening, usually toward the bottom. It is essential that the paper envelope of the nest not be broken open during treatment or the irritated wasps will scatter in all directions, causing even greater problems. Hornets are far more difficult and dangerous to control than other social wasps. Hornet nests may contain thousands of wasps which are extremely aggressive when disturbed.
Stinging Pest Control - Wasps, Hornets, Bees, Etc.