By Daren Mueller, Extension Plant Pathologist
In 2004, the Soybean Rust Fast Track System was put in place to ensure rapid identification of soybean rust through First Detectors and Triage Team Members. Over the past four years, more than 700 individuals were trained as First Detectors or Triage Members as part of the Iowa Soybean Rust Fast Track System. While soybean rust did not infect fields in Iowa until late 2007, we feel that the Fast Track System training helped Iowa growers and agribusinesses through many of the unknowns surrounding soybean rust.
One lesson learned while scouting for soybean rust in the southern states and in confirming the first occurrences of soybean rust in Iowa in 2007 is that the identification of the disease in the field at low incidence (less than 10 percent of leaves infected) and severity is very difficult. To identify low levels of soybean rust, leaf samples must be incubated and observed in the laboratory using a microscope, not observed for lesions and pustules out in the field.
A microscope is required to identify low-levels of soybean rust on soybean leaves.
One of the main responsibilities of the First Detectors and Triage Team Members was to filter out samples suspected of being infected with soybean rust that were clearly infected with other foliar diseases, not rust. However, because of the difficulty identifying soybean rust in the field, the functioning of the Fast Track System is being changed. First Detectors and Triage Team Members will no longer be asked to filter out samples with other soybean diseases.
The new role of First Detectors and Triage Team Members is to serve as a conduit to get samples submitted properly to Iowa State University. If soybean rust is suspected in a particular field, samples should be submitted to the ISU Plant and Insect Diagnostic Clinic even if tell-tale lesions and pustules are not observed. We are in the process of writing a new publication explaining how to submit a sample for early and accurate diagnosis of soybean rust.
Daren Mueller is an extension specialist in the Department of Plant Pathology.