Drought Stressed Trees and Shrubs

We are seeing signs of drought effects on trees and shrubs across mid-state now. The following are some thoughts on the current situation.

• Premature leaf drop is occurring in drought stressed trees and shrubs due to the drought condition. With the drought in 2007 and now stress in 2008, expect long lasting effects. Trees and shrubs that have been severely stressed for two years in a row will have much reduced food reserves due to lowered photosynthesis. Winter survival may be affected and you may see more trees and shrubs that do not leaf out properly in the spring.
• Drought also reduces the amount of defensive chemicals that stressed trees and shrubs can produce making them more prone to damage from insects and diseases. Late season borer damage would be an example.
• We have very limited subsoil moisture reserves in many areas. This will be a concern as we go into the fall. Root death may occur and this can lead to increase in root rots over the winter when rains do occur.
• It is critical to water stressed trees and shrubs before leaf drop occurs. Water deeply - shallow watering will not help plants recover sufficiently. Limited rainfall (less than 0.5 inch) also will not be enough and additional water will be needed.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County