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What’s on my Soybean Leaves? (07/19/18)

I have been getting questions about disease lesions appearing on soybean leaves.

What’s on my Soybean Leaves?

I have been getting questions about disease lesions appearing on soybean leaves. 

The majority of what I have seen is bacterial blight, which is generally not of economic concern, and even if it was, it cannot be managed with fungicides.  I have also seen Septoria brown spot, another disease that is also not usually economic important.

I am providing more information on both diseases, but I thought I would use the Soybean Diagnostic Card Series that was published this past winter to help explain them.  The Card Series has information on 23 diseases, with images on the front of the card and a description of key symptoms and other important information on the back.  My colleague at the University of MN (Dean Malvick) and I wanted to create something that was specific to our region and selected a high quality synthetic material for the card surface that is resistant to water, creasing, tearing and light reflection.  The set consists of 24, 3½” x 8” cards bound by a single ring; and it is field worthy! 

I am including the disease cards for Bacteria Blight and Septoria brown spot in this article.  The ‘Symptoms’ and Figures should help you identify the disease, the ‘Factors favoring development’ provide details about when the disease may occur and ‘Important facts’ often discuss geography, yield loss and what the disease is commonly confused with.

The pdf version is free for download at  and sets of cards are available by  or 701-231-7881.

The Soybean Disease Diagnostic Series is a joint effort by NDSU and the University of Minnesota. We thank the North Dakota Soybean Council and the Minnesota Research and Promotion Council for supporting the development and funding this publication.

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Sam Markell

Extension Plant Pathologist, Broad-leaf Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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