Soybean rust reached farther north in 2006 than ever reported and inundated coastal areas from South Carolina to Virginia. Despite it’s dramatic late season activity, the dreaded disease did little damage to the 2006 U.S. soybean crop.
By the time rust reached west central Indiana, the most northerly infections reported, all the full season crop was harvested and frost had taken out double-crop beans. The heaviest infestations in 2006 were along the Atlantic Coast and to the west along the Mississippi River.
Researchers in Indiana report the rust spores that infected soybeans in that state likely came from Louisiana in late September, but did not develop until later in the season — too late to be a factor in the 2006 crop.
Whether the more northerly migration of the disease in 2006 means more trouble for 2007 is open for debate. In the winter of 2005-2006, rust over-wintered as far north as Montgomery, Ala., on kudzu. Yet, Alabama was one of the least affected states by rust in 2006.
Likewise, very little over-wintering rust was found in Louisiana, yet that state seemed to be the hot-spot for growth and movement of rust.
By first frost, Louisiana, Arkansas, Tennessee, Missouri, Illinois and Indiana had reported rust. All these cases moved northward from Louisiana, generally following the Mississippi River. Only in southern Mississippi and Louisiana did the disease get to soybeans in time to be a problem.
Even in these states, spraying for rust was at a minimal level.
Similar spread of the disease occurred in the Carolina’s and into south-central Virginia. Only in a few cases in South Carolina was one fungicide spray recommended for rust management. Though widely reported in Georgia, the disease did not create major problems in 2006, likely due to an extended drought in major soybean producing areas of the state.
By harvest time, rust was much more prevalent in the Carolinas than it was in Georgia.