i have a retaining wall built around my driveway which seems to attract wasps. i know for sure there are nests throughout the wall. the wall is built out of versa lock block . the wasps love to just congregate on the wall during the day which becomes a nuisance for friends and family. is there any type of product which i can spray over the entire wall to control and prevent. cypermethrin? and how often would the treatment need to be made since the wall is exposed to rain.