Asian soybean rust could be a “no-show” for this season.  Although we continue to get reports of new locations with soybean rust in southern states, infection levels are still generally low.  An exception is a research plot at Tifton, Georgia where a rust hotspot has developed within a research plot and the characteristic soybean defoliation has been observed.  This is still a very small area.  No one has, as yet, been surprised to wake up and find that an entire field is showing symptoms that are common with severe rust infections.  There has also been additional geographic spread of the disease, with an infection point detected in a soybean sentinel plot in Effingham County, Georgia in the eastern part of the state (up against the state line shared with South Carolina) and, now the farthest north occurrence of rust, in a sentinel plot in Laurens County, central Georgia.  All in all, however, this still does not increase the risk for the Midwest.

Weather conditions in the GROWMARK trade area remain generally unfavorable for soybean rust infection and spread.  In spite of this, the seasonal increase of soybean height and canopy density, along with daily dew and moderate temperatures, still could provide a favorable environment for localized infections.  This is demonstrated by the prevalence of downy mildew and other foliar diseases.

Soybean maturity will soon put most fields beyond risk for significant problems from soybean rust.  Within the next two weeks, most soybean fields should be out of danger of having severe rust infection.  Late-planted and double crop soybeans will continue to require frequent scouting.  Following is a summary table of seasonal soybean rust infections, to date.

by Kevin Black, GROWMARK