A. James Downer

Native Diseases of California Mediterranean Forest Angiosperms

Disease is an interaction with host plants and their environment and a biotic agent (pathogen) which changes host physiology resulting in symptoms of changes in growth, reproduction or longevity. While the pathogenic agent can be in the form of bacteria, mollicute, nematode, parasitic algae, parasitic seed plant, virus, or fungus, not all of these agents result in the formation of diseases that significantly limit populations of woody plants. Fungi are dominant pathogens of Mediterranean Forests. Fungi cause disease in all parts of woody plants but their impact can be summarized by examining the disease they cause in the major organs of trees. This chapter discusses important diseases of the foliage, shoots, periderm (cankers) and woody systems (main stem) and root systems of trees. In each section, a detailed description of the disease category is given along with descriptions of symptoms, diagnostics and etiology of the pathogens. Each disease category is accompanied by an introductory section that reviews environmental conditions that facilitate disease development. Adaptations of fungi to the Mediterranean climate of California are mentioned throughout the chapter.