The major root diseases of forest crops and tropical plantation crops worldwide are discussed. The problems of determining the populations of pathogens in soils and the factors that affect them are analyzed. Discussions are presented on the use and application of mathematical theories and models. The significance of population levels of some of the most widespread pathogens to disease incidence is also evaluated, and the biological consequences of soil fumigation and soil heat treatment are explored in terms of the soil flora, plant responses, and the physical factors of the soil. Likewise, the effects of root exudation on infection - an active area of research in the past few years - are investigated with several of the more important pathogenic fungi and parasitic nematodes. Two chapters deal with subjects not treated in the first volume: the genetic aspects of behavior of sil-borne pathogenic fungi and the effects of soil moisture and aeration on pathogens and pathogenesis.
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