Such thinking is obvious during a series of 90-degree scorchers and no rain or when winter temperatures plunge to record lows. This refers to the long-term stresses on plants from previous seasons. Though Central and Southern Ohio were hit worse than Northeast Ohio in 1999, we should all remember that 1999, especially from spring through midsummer, was very stressful on plants. The past predicts the future when it comes to woody plant health. Let's look at a few examples.
Many spruces suffer from a disease known as cytospora canker.
This fungal disease causes sap-oozing cankers on branches, typically low on the plant, gradually causing these branches to die from the bottom of the tree up over a period of years. Research shows that cankers are more common on drought-stressed plants, with the disease getting a foothold during dry periods. Cytospora canker is especially severe on Colorado blue spruce and it is important to note that this disease is far less frequent on Colorado blue spruces growing in their natural Rocky Mountain range. Another common disease of certain trees and shrubs is verticillium wilt. This is caused by a fungus that infects plants through the root system, then spreads upward through the conduction system of the plant.