ABSTRACT
Forest etiology, which deals with the causes of diseases, either infectious agents (biotic), such as bacteria, viruses, and fungi, or noninfectious agents (abiotic), such as environmental factors including heat, cold, nutrient deficiencies, air pollution, and genetically induced factors. Like all plants, forest trees are subject to injury and disease caused by adverse environmental influences, including other organisms. They may be affected at all stages in their life cycle, from seed to mature tree. Diseases produce a variety of effects and can cause losses in economic, environmental, recreational, and aesthetic values produced by the forest. In forestry, tree diseases are caused by a diverse range of organisms, including fungi, oomycetes, bacteria, phytoplasmas, parasitic higher plants, viruses and nematodes. Among these, the fungi are the largest group causing disease in forest trees. Different Phytophthora spp. belonging to the oomycetes group is also important as the causal agent of several devastating diseases on trees especially under nursery.
