This will depend largely on where you live and when the mud daubers get active. It's important that you get it out early enough to help keep them away during the beginning of the season. For us here in Georgia, that would be this month as flying insects are already starting to move about and start new nests. A good dose of Cypermethrin now will really help. Mud Daubers do start early too so don't let them get started ahead of you; a good rule is to treat at least one month before you normally start to notice them.