Kansas soybean disease update
click image to zoomPhoto courtesy of Dept. of Crop Sciences, University of Illinois.Pythium blight in soybeans. Heavy rains in May and June over parts of north central, northeast, and east central Kansas resulted in the highest incidence of Pythium seedling blight in recent years. Disease pressure was so high that even where a fungicide seed treatment was used, some fields suffered significant stand loss. Many fields required spot or complete replanting. Some fields with isolates of Pythium that tolerate higher soil temperatures continued to have problems even in to July.
Except for areas north of U.S. Hwy 24, the rainfall was sparse in the critical months of June, July and August. Common foliar diseases such as brown spot and frogeye leaf spot were absent from most fields except along the Nebraska border. The hot, dry weather proved to be highly favorable for the development of charcoal rot, bringing statewide losses to the highest levels since 2006.
On the positive side, because of lower rainfall amounts, soybean sudden death syndrome was at its lowest level since the 2005 growing season, being confined mostly to irrigated fields with a previous history of the disease.
click image to zoomPhoto by Stu Duncan, K-State Research and Extension.Field of soybeans in northeast Kansas, spring 2011, showing stand loss due to Pythium blight. A statewide survey for soybean cyst nematode (SCN) started in 2011 is revealing that less than 10 percent of Kansas soybean fields are infested, and the majority of these have SCN levels in the range where only low to moderate losses are likely occurring. In some counties such as Cherokee County in southeast Kansas, however, the percentage of fields infested is approaching 50 percent — with a few having nematode levels that are likely causing significant yield loss.
Other diseases identified in 2011 include bean pod mottle virus, Phytophthora root rot, stem canker, bacterial blight, and iron deficiency chlorosis.