Plant Disease Management

Plant disease management of trees, shrubs and turf starts with selecting disease resistant plant material. Many of the newer cultivars available today are resistant to powdery mildew, leaf spot and other diseases.

Be careful when planting in wet soils. Many plants like Rhododendron can develop root rot if planted in soils that are poorly drained. Many others can almost be drowned. Knowledge of a plants tolerance of wet soils is critical.

Proper irrigation practices must be followed. In general, it is far better to water deeply once a week than lightly several times. Leaves that are constantly wet are more susceptable to infection. Do not water at night. Watering should be done early in the morning so that leaves can dry off during the day.

Air circulation is also a key. Air circulation may be improved by proper pruning. Plants must be pruned in a way so that air can circulate throughout the plant and dry wet leaves. When pruning certain species like Photinia and Euonymus during the growing season, only make thinning cuts. Heading cuts will stimulate new growth that can be highly susceptable to infection.

Sanitation is important. Rake up and remove fallen, dead leaves from diseased trees and shrubs. This will help reduce outbreaks the following year.

Be careful when fertilizing. Excessive nitrogen fertilization can also lead to disease outbreaks.

Most plant diseases are caused by fungi. A fungicide spray program may be implemented on high value plants with a history of disease. This requires a thorough understanding of disease management principles.

Sudden oak death has recently moved into the area. This is a serious disease with no known cure.