Entomology and Plant Pathology, Oklahoma State University
127 Noble Research Center, Stillwater, OK74078
Vol. 11, No. 30
Jun 6, 2012
Soybean Rust Update
John Damicone, Extension Plant Pathologist
Rick Grantham, Director, Plant Disease and Insect Diagnostic Laboratory
Soybean rust (SBR) (Fig 1) is an invasive foliar disease of soybeans. The disease causes premature defoliation and can reduce yields by up to 50% when severe. The disease overwinters along the Gulf Coast on kudzu during mild winters. Due to the mild winter this year, soybean rust survived the winter well on kudzu in several Gulf Coast States. However dry conditions this spring along the Gulf have limited disease development thus far in 2012 and until last week, no reports of the disease on soybean had yet been made. Soybean rust now has been reported on soybean in the Rio Grande Valley where it has been found at moderate levels on soybeans at the R1 (first bloom) stage (Fig 2). The disease could threaten soybeans in Oklahoma later in the season depending on weather. Apparently there are only about 300 acres of soybeans in the Rio Grande Valley this year, which will limit the spore load released from this area. The disease will likely have to increase on soybeans further north in Texas before it threatens the Oklahoma soybean crop.
Fig 1. Soybean leaf infected with soybean rust.