By Daren Mueller, Department of Plant Pathology and Microbiology
One thing we have learned from outbreaks of sudden death syndrome (SDS) in years past is that this disease likes it wet. Last year we wrote about the risk of SDS increasing with the early season rain. But at the end of the article we threw in one caveat — soybeans were planted very late in the season, which reduced the risk of SDS developing. And after we published the article, the rains essentially stopped. Fast forward to the end of the 2013 season -- we still had some SDS in parts of Iowa in 2013, but it was not as nearly as bad as it could have been.
This year's rain is triggering a similar increase risk in SDS developing. Unlike last year, most of the soybean crop was planted before the bulk of the rains started which further increases the risk of SDS. The early wet weather we have experienced so far in 2014 helps increase the root rot phase of the disease. Revisiting the table published in a Plant Health Progress article, one of the driving factors for late-season SDS development is significant rainfall during the late-vegetative and early reproductive stages. The totals in June 2014 are near the numbers in the SDS years throughout much of Iowa. For example, the precipitation total in Ames during June was 10.23 inches.
Remember there are a few other diseases that may be confused with SDS such as brown stem rot and stem canker. Look for lesions on the outside (stem canker) and browning in the pith (brown stem rot) to distinguish from SDS.
Average total precipitation in four years with high SDS prevalence (1993, 1998, 2008, 2010) and five years with low SDS prevalence (2001, 2004, 2005, 2007, 2011). Values are means of two locations: Ames (central Iowa) and Mount Pleasant (southeast Iowa).
zMean for the period of 1981 to 2010 at Ames and Mount Pleasant, Iowa
Daren Mueller is an extension soybean pathologist and assistant professor in the Department of Plant Pathology and Microbiology. He can be reached at 515-460-8000 or email@example.com.
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