Diseases of citrus.

This chapter reviews the production, distribution and taxonomy of citrus crops, together with the distribution, importance, aetiology, epidemiology and control of their diseases. Most diseases of fruit and foliage do not cause direct loss of trees and the degree to which they must be controlled depends on whether the crop is destined for the fresh market or for processing. Root diseases such as Phytophthora spp., foot rot and gummosis (caused by Phytophthora citrophthora, P. palmivora and P. nicotianae) can cause substantial losses, though diseases caused by systemic pathogens are arguably the most severe of all. These include citrus tristeza virus, citrus blight and citrus variegated chlorosis (caused by Xylella fastidiosa) which have caused losses in many areas of the world.