Nearly all pathogens spend part of their life cycle on crop residues. Residues affect the physical and chemical environment of the soil. Residues also act as organic amendments to intensify microbial activity. Maximizes primary inoculum. Refer to previo us discussion.
Inoculum is in close proximity to developing crop.
Maximizes chance for infection. Each spore's probability of success in enhanced. In no-till corn Pythium sp. , and in soybeans, Phytophthora sojae may become problems un der conditions of lower soil temperatures and saturation by increasing the probablity of successful infections byzoospores and decreasing seedling vigor. Amount of disease can be directly correlated with amount of residue left on surface of field. When pathogens form survival structures capable of prolonged survival in soil e.g. soybean cyst nematode not greatly influenced by tillage, because cysts are capable of survival in soil for more than a single year.