ISU Extension to Agriculture and Natural Resources

Know Your Spots: Hands-on Training on Foliar Disease Identification in Soybeans

Alison Robertson, Assistant professor, Plant Pathology

Asian soybean rust (ASR) is a devastating foliar disease of soybeans, which results in premature defoliation and reduced yields. ASR was discovered in Louisiana on November 10, 2004. Within a few weeks, the disease was found as far north as the boot heel of Missouri. There are a number of common foliar diseases in Iowa that can be confused with ASR because they cause similar leaf spot symptoms. Therefore, there was concern that the Iowa State University (ISU) Plant Disease Clinic would be flooded with look-alike diseases with the heightened concern of ASR occurring in Iowa. For this reason the Rust Fast Track System was initiated to filter through the possible ASR cases in Iowa.

Objective

To provide hands-on training on the identification of common leaf spot diseases of Asian Soybean rust and to pass these samples onto educated Iowa Soybean Rust Team Triage and First Detectors.

Activities/Output

Six clinics were held at the Field Extension and Education Laboratory (FEEL) in Boone, Iowa during June 2005. Soybean plants were inoculated in the greenhouse with brown spot, bacterial blight and bacterial pustule pathogens. Resin-embedded leaves infected with ASR were provided to ISU Extension by the North Central Soybean Research Program. Alison Robertson gave a PowerPoint presentation, Know Your Spots, to participants highlighting the identifying characteristics of each foliar disease that occurs in Iowa on a macroscopic and microscopic scale. Likely conditions for the development of each disease were also discussed. After the presentation, attendees had the opportunity to practice on live material. Dissecting scopes afforded a microscopic view of the disease symptoms. Attendees also learned how to use hand lens in the field. Two ISU Extension publications (Pm1985, Triage Identification Guide for Asian Soybean Rust and Other Diseases and Pm1992, Identification of Common Soybean Leaf Diseases and Asian Soybean Rust for Iowa First Detectors), were provided to Triage and First Detectors.
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Impact/Outcomes

No ASR was reported in Iowa in the 2005 growing season.
Reports were received of First Detectors and Triage being called out to fields suspected of ASR infection; however, they were able to identify the disease and confirm it was not ASR.
The ISU Plant Disease Clinic only received 2 samples via the Rust Fast Track System. This translates to a considerable amount of time and expense saved in the clinic.
Many of the First Detectors and Triage reported back to Alison Robertson on the usefulness in their respective publications.

2005
142 - Integrated Pest and Crop Management

Page last updated: July 9, 2006
Page maintained by Linda Schultz, lschultz@iastate.edu