David A. Rosenberger

More than 350 diseases are known to affect temperate zone tree fruit. However, the majority of economic losses are attributable to fewer than 50 diseases, most of which are caused by fungi or bacteria. Viruses account for more than 50 percent of the known pome and stone fruit diseases, but many are relatively uncommon. Nematodes are the direct cause of a few diseases, and they contribute to others by vectoring viruses or by predisposing trees to pathogen attack. Diseases can also be caused by abiotic factors such as plant malnutrition, cold injury, or oxygen deprivation in water-logged soils.

Comprehensive descriptions of diseases and disease management programs are available in the publications cited at the end of this chapter. Management strategies vary significantly from one geographic region to another because of differences in climate, cultivars, pest complexes, and market objectives for the crops involved. Local and state extension systems can often provide the best regionally adjusted recommendations for disease control.

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