why not just turn back the tide? Unless you spray a large area, i.e., neighborhood you are just wasting the customers money and needlessly dumping pesticide into the environment.
A better idea would be to make sure birdbaths are flushed daily, no standing puddles and that goes for flower pots, tires, trash cans etc.
Yesterday is a memory. Tomorrow is a mystery. Right now is your reality.
(Thx to GB, RIP)