what is the best overall spray that i can prevent most disease and insects

to NGA

Dormant oil sprays with lime-sulphur mixed in will get rid of over-wintering insects and eggs. It is usually administered 2 times, once during late fall or winter and once in early spring before the buds open (I always sprayed at Thanksgiving and Valentine's Day). You want to do it when the temperature is above freezing so a lot will depend upon where you live. You will need additional sprays in the warmer months if problems arise.

I just found this great PDF:

http://ext100.wsu.edu/chelan-d...