Conventional tillage methods are effective means of controlling plant disease because completely burying crop residues destroys plant pathogens and breaks disease cycles (Boosalis et al, 1986). Today, cropping practices are shifting to surface-tillage systems to offset the rising cost of production and to comply with USDA/ ASCS mandatory soil conservation requirements which have a deadline of 1 January 1995. The percentage of no-till soybean fields in Iowa was 19% of total acreage in 1993. It is predicted that the total acreage of conservation tillage in Iowa will increase to 11 million acres by 1995. Because conservation tillage practices leave crop residues on the surface and change the physical environment of the soil, it will undoubtedly change the disease picture (Cook et al, 1978). A national survey of farmers by Conservation Tillage Information Center (Gebhardt et al, 1985) showed that pest problems increased and became one of the major obstacles to adoption of conservation tillage.