Environmental changes causes stress. At El Nino. Pollution causes stress. Chemicals cause stress. Do things more organically.
High nitrogen causes stress.
Avoid high nitrogen fertilizers. So whether its a sick tree, sick plant, sick rose or sick lawn, follow the steps above first before you do any thing else. Last but not least. 2 Immediate Damage Control inspect plant for any damaged areas, remove any if possible. Fruit related diseases require proper temp proper water proper ph level of soil insect or animal vector mineral deficiency's 4 Spray area affected with any one of many natural disease controls I have mentioned in my book or on website.