General, Regional Soybean Disease Update: September 4, 2011

Current U.S. soybean rust situation as of September 4, 2011.

The information included in this blog update originated from the soybean rust telephone conference held on August 29, 2011.

Alabama – Hot and dry conditions with little to no rainfall in the southern part of the state have reduced the likelihood of soybean rust or most foliar soybean diseases.  However, there are a lot of late soybeans planted throughout the state.  Charcoal rot is the one disease that has been identified with regularity.

Florida – Soybean rust has most recently been confirmed on kudzu in Leon County.  However, soybean rust has started to be identified later than normal compared to the recent past.  Environmental conditions have been hot and dry throughout the panhandle of Florida.  In addition, soybean rust was identified on R6 soybean plants from a sentinel plot in Gadsden County but rust was present at incredibly low levels with only a single leaf out of 100 having soybean rust signs present.  The confirmation of soybean rust on soybean is the first for the U.S. in 2011.

Georgia – Conditions remain hot and dry throughout much of the state.  No soybean rust has been identified even with the close proximity of the disease in Florida.

Louisiana – Soybean rust has only been observed in Iberia Parish on kudzu.  Hot and dry conditions have occurred throughout much of the season in LA meaning that soybean rust couldn’t reach the high levels of inoculum that appear to be required before the disease can move further north into the soybean production area.

Southern blight of soybean. The main characteristic of the disease is the white mycelium growing on the stem.

Mississippi – High temperatures and little to no rainfall in parts of the state have meant little disease is present in the soybean crop.  However, depending upon geography aerial web blight, frogeye leaf spot, soybean vein necrosis virus, southern blight, and black root rot can be observed.  With the cooler temperatures following Tropical Storm Lee, aerial web blight will shut down since the disease prefers hot, dry weather.  Southern blight (also referred to as Sclerotium blight) isn’t a frequent disease in MS and typically when observed will likely be a few plants together in one area of the field (see photo).  In addition, Cercospora blight (or late-season Cercospora) has been regularly observed regardless of location within the state.  In the four years that I’ve been here I think we can safely say that Cercospora blight is the worst this year of any of the past 4.  But, with all of that said no soybean rust has been observed in MS so far this season.  However, with the Tropical Storm that will impact much of the state over the weekend of September 3-5 this will likely increase the potential of the disease being identified.   

South Carolina – No soybean rust and much like the rest of the region conditions are hot and dry throughout much of the state.  Attention with regards to identifying soybean rust has shifted to the eastern side of the state following the rainfall that occurred during Hurricane Irene.