Foliar Fungicides in Seed Corn Production

Since 1982, we have conducted a program to determine the fungicides that may be effective for controlling foliar diseases in inbred and hybrid com.For the past seven years we have limited our research to only inbreds or sister line hybrids.In 1990, we started a cooperative program with seed companies and have conducted our research in commercial seed production fields in five greatly different years in terms of weather patterns.Thirty experiments have been established in seed production fields and 25 fields have been harvested for yield.Five experiments were abandoned because of herbicide injury interactions (2,4-D) with the fungicides, excessive Stewarts disease (a bacterial disease that can not be controlled with fungicides and was devastating), or drought. Years of ExperimentationIn 1990, moderately wet conditions and mild temperatures prevailed before detasselling and then it was very dry with moderate temperatures for the balance of the growing season.In the central, southern, and southeastern parts of the state where we had the fungicide trials, we experienced heavy Stewarts disease, because of the mild winter.In spite of this, we had common rust, gray leaf spot, and Northern com leaf blight as the dominant disease in different experiments.The next year, 1991, brought drought conditions throughout most of the growing season.Of the four sites selected for experiments in eastern and southern Iowa, only two escaped the drought adequately and had gray leaf spot development.The disease developed slowly through most of the growing season and became quite heavy by late August.