Pretty colors for leaves on a houseplant, but not on soybeans, as sudden death syndrome has prevailed over many Cornbelt acres this year, brought on by early season sogginess. It is the second leading cause of yield loss (behind SCN). Several land grant universities (Purdue, IA St., WI) are collaborating on a website to help farmers fight the disease at www.soysds.com.
Conditions have been near perfect for SDS in soybeans this year, based on research by IA St. plant pathologist Darren Mueller. His findings include: (1) early planting increases the likelihood of conditions being good for root infection. (2) a cool, wet spring improves conditions for root infection, (3) a heavy rainfall in June is important for SDS to spread, (4) heavy rains during reproductive growth stages increases toxin production.
You may have some problems in soybeans that appear to be SDS-related, but are not. Instead, it could be brown stem rot. Leaf symptoms are similar, but stem appearances are different. Stems need to be cut open length-wise, and if the pith has brown spots, the disease is brown stem rot. That will need to be addressed the next time you order seed beans for that field.
Excerpt from Cornbelt Update Sept 7, 2015 Vol. 17 No. 3
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