Theres no such thing as prevention only treating a prob u have and u don't have one, Pesticides have little residual effect. my advise is to put down some diatomaceous earth that'll knock out any eggs in your soil and will add silica to the nute profile and that's good.
if u dilute the stuff ur spraying to 1/4 strength u can start even a month in is my guess. pesticides don't affect plants as much as herbicides.
I'm a lil stoned sorry for the rant, lol
edit: I used to spray pesticides for a living...try not to spray in temps over 90F. in full sun especially...it'll burn.