David--you don't have to spray!!! It's expensive and bad for you and bad for the environment!!! Just a few months ago the magazine Organic Gardening ran an issue with the cover story "Confessions of an Apple Grower" about how to get fruit from fruit trees w/out spraying. And this month's issue has a followup (I just read it, but I don't remember all the details), encouraging fruit tree growers to resist the urge to spray. There are organic alternatives, esp. a new pheromone bait that pulls the disease carrying bugs away from your trees and onto sticky traps. I don't have the article in front of me (it's at home, I'm at work) but I'd be happy to give the reference/details if there's any interest. Wendy