ABSTRACT

INTRODUCTION Disease leads to harmful changes in the appearance of a tree compared with a healthy individual, altering its growth, reducing amenity value and yields, or even killing it. Although symptoms may be striking, the diagnosis of individual diseases requires a broad knowledge of trees and of the different disease categories affecting them. Factors other than disease, such as poor environmental conditions and nutritional limitations, can also result in abnormal growth, while careless use of herbicides or de-icing salts can also cause damage.