The two keys to spraying any wasp or hornet nest are maintaining distance and timing. The farther away you can be from the nest while spraying, the better. Most wasp and hornet colonies are active during daylight hours, and become dormant in their nest after dark, so spraying in the evening is best.
If we look at the most aggressive species, it would have to be the bald-faced hornet (Dolichovespula maculata). If you have the tools to spray a bald-face hornet’s nest, you will be able to spray the others as well. Bald-faced hornets are unique because they are larger and have distinct black-and-white markings, instead of the common black-and-yellow markings.
Bald-faced hornet colonies can average 500 workers or more. They build brownish-gray paper nests, and will aggressively defend their nest whenever they feel threatened. Bald-faced hornets have the ability to assess a threat; they will swarm and pursue an attacker, inflicting multiple venomous stings.
Most people’s reaction to bald-faced hornets is to destroy them as quickly as possible, but they do help control flies, spiders and caterpillars, so if the nest is in a safe area and far away from people, another option is to just let them exist.
from Pest Management Professional https://www.mypmp.net/2019/01/10/maintaining-distance-when-spraying-stinging-insect-nests/