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The Iowa Soybean Pod Test for Predicting Phomopsis Seed Decay in Kansas. D. J. Jardine, Assistant Professor, Department of Plant Pathology, Throckmorton Hall, Kansas State University, Manhattan 66506-5502. Plant Dis. 75:523-525. Accepted for publication 19 November 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0523.

The Iowa pod test for predicting the need for foliar fungicide applications to control Phomopsis seed decay of soybeans (Glycine max) was evaluated under Kansas growing conditions. The mean incidence of pod infection by Phomopsis longicolla was 50, 15, and 50% in 1987, 1988, and 1989, respectively. No correlation was found between the incidence of P. longicolla on pods at soybean growth stage R6 and either the incidence of the fungus on seeds or the germination of seeds at harvest. For seeds from plants treated with benomyl, the percentage of pathogens detected was not significantly different from that of seeds from unsprayed plants in 1987 and 1988. In 1989, Penicillium spp. occurred at significantly lower levels and Alternaria and Fusarium spp. at significantly higher levels on seeds from benomyl-treated plants than on those from unsprayed plants. Seeds from plants treated with benomyl at growth stage R7 had a significantly higher level of seed germination than seeds from unsprayed plants following harvest in 1988 only. Under Kansas growing conditions, the model consistently predicted the need for foliar sprays when they were not needed.