Most “sick tree” problems can be traced back to underlying stresses that have reduced the tree's vigor, making it more vulnerable to diseases or insect pests.
Excessive summer irrigation of oak and madrone trees may promote fungal diseases such as the oak root fungus (aka armillaria root disease) and crown rot.
Pacific Northwest blueberry growers must identify and control a number of bacterial and fungal diseases in order to ensure the highest yields. Fortunately, only a few of the diseases that occur on highbush blueberry in this region cause significant losses when left unchecked.
A guide for how to collect and where to get a sample analyzed for plant diseases.