The genera of Phytophthora and Pythium are two of the very destructive groups of plant pathogens in the world (Plaats-Niterink, 1981; Erwin and Ribeiro, 1996). They attack mainly mature plants and young seedlings, respectively, of forest, fruit, vegetable, flower, and ornamental species. These two groups of fungi are classified in the family Pythiaceae of the Oomycetes, which is excluded from t...

Several plant pathogenic fungi affect soybean plant health at different growth stages (Table 1). Although infection may occur early, many of these pathogens do not cause apparent symptoms until later growth stages. Frequently seedling health is ignored because plant populations are acceptable and stem and leaves do not express symptoms during early vegetative growth. Phytophthora sojae, Pythium...