In the 1997 and 1998 growing seasons, some soybean fields had plants with bright yellow leaves and plants that were dying from the top down, a condition called top dieback (growers may call this condition tip blight). Top dieback was pronounced in 1997 and 1998 from late July to mid-August when most soybean plants were in the reproductive phase. Top dieback showed up again this year.
Iowa State University
Sanogo, Soum and Yang, X. B., "Soybean top dieback shows up" (1999). Integrated Crop Management News. 2221.