Wear protective clothing, such as a thick jacket, long pants, thick gloves and a hat, when killing wasps. If you have a protective mask, wear that as well.
Identify the wasp's nests in the day. Try to locate as many as possible so that you can eliminate them all at the same time. Do not try to kill the wasps during the daylight hours. Wasps are more active and ready to sting during the day, and they are more likely to be away from the nest.
Spray the nests with wasp-killing spray placed in a pump sprayer to kill any adults present in the nests. Allow the spray to rest on the wasps for several minutes. Use a ladder, if necessary, to reach nests that are high up.
Knock down the nests and kill any larvae inside. Dispose of the nests in a trash can.
Spray the area where the wasps built the nests with a long-term insecticide spray. These sprays linger and deter new wasps from building in that location again, and will also kill any wasp that touches it.