I tend to agree with SDSU.........Though around here, its NOT a popular beleif.   We sprayed when they started to reach 100-150.  Seems like when the buggers hit those numbers, its 24 hours and there is over 300.   Given this years lack of moisture in Late June and all July, I wasn't fond of 100 bugs suckin juice out of a plant that has nothing to replace it.

Might have to spray again, time will tell, but in my experience, another application has paid for itself, aside from my rear getting soar in the 6000 trike.