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. Symptoms similar to those of what we call tip blight in soybean were first observed in Ohio 18 years ago and the disease was named top dieback. In Iowa, the disease was first reported to the Iowa State University Plant Disease Clinic in 1997 by Jim Facewtt, extension field specialist-crops, and Jerry Long, Ceder County Extension director. Initial symptoms of top dieback are yellowing and death of leaves in the upper portion of the plant canopy followed by discoloration of internodes.
Plants die prematurely when the disease is severe.
An Ohio study showed that fungal species belonging to the genera Phomopsis and Diaporthe , a group of plant pathogens that cause various diseases in soybean, are associated with top dieback. Soybean field with top dieback. Top dieback can be misidentified as severe cases of sudden death syndrome. Although both diseases are different in the early stages of symptom development, their symptoms are similar in the later stages, especially in terms of premature dying when affected fields are observed from a distance. For sudden death syndrome, close examination reveals well-defined interveinal chlorosis or necrosis on leaves at any position in the plant canopy.