I have been given this web page to tell me when you should spray apples and cherries. It tells what bug is hatching by the degree days. I actually inputs weather data for you and tells what is hatching out or blooming. There is a section on the site to create your own.
http://pnwpest.org/wea/weaexp.html
why is it that we cannot come up with an amount of degree days to determine swarming?