i am a pest control professonial and this is an easy DIY thing.There are chemicals homeowners can use and be safe.Wasp,Hornets,Yellow jackets can easily be killed with something called wasp freeze.(found in your local hardware store,Lowes,Home Depot,etc.)Usually the best time to do this is in the morning or late in the evening when they are in the nest.This chemical usually shoots about 20 ft. to keep you away from the nest.If not afraid of being stung the best place to first treat is the exit hole on the nest.Spaying this area first causes the bees dying to block the hole so the live ones can't get out.Then pierce the nest with an aerosol can using a straw to treat the interior of the nest.I hope this is helpfull.