Field incidence and Sporecaster prediction of Sclerotinia stem rot ascospores and apothecia in various crops and rotations

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2021-01-01
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Straka, Shannon
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Daren S. Mueller
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Plant Pathology and Microbiology
The Department of Plant Pathology and Microbiology and the Department of Entomology officially merged as of September 1, 2022. The new department is known as the Department of Plant Pathology, Entomology, and Microbiology (PPEM). The overall mission of the Department is to benefit society through research, teaching, and extension activities that improve pest management and prevent disease. Collectively, the Department consists of about 100 faculty, staff, and students who are engaged in research, teaching, and extension activities that are central to the mission of the College of Agriculture and Life Sciences. The Department possesses state-of-the-art research and teaching facilities in the Advanced Research and Teaching Building and in Science II. In addition, research and extension activities are performed off-campus at the Field Extension Education Laboratory, the Horticulture Station, the Agriculture Engineering/Agronomy Farm, and several Research and Demonstration Farms located around the state. Furthermore, the Department houses the Plant and Insect Diagnostic Clinic, the Iowa Soybean Research Center, the Insect Zoo, and BugGuide. Several USDA-ARS scientists are also affiliated with the Department.
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Plant Pathology and Microbiology
Abstract

Sampling ten similar fields for Sclerotinia sclerotiorum ascospores and apothecia was done to determine if different crops and crop rotation history had an effect on incidence of Sclerotinia Stem Rot inoculum. All fields were near Livingston, Wisconsin with similar soils, were within five miles of each other, and had some recent history of Sclerotinia Stem Rot. During the previous five years, each field had corn, soybean, and small grains in varied rotations, utilizing different management strategies for each crop. The forecasting application, Sporecaster, also was used to record the Sclerotinia Stem Rot risk level for all fields during the 2019 growing season to evaluate if Sporecaster risk levels matched apothecia development and ascospore release in actual field conditions. To trap ascospores, eight plates of potato dextrose agar supplemented with bromophenol blue and antibiotics were placed in each field sample area weekly during July and August, 2019. At the same time each week, multiple visual observations were conducted in each sample area for apothecia. Throughout the four week study, Sporecaster showed “low” risk for Sclerotinia Stem Rot, zero apothecia were observed, and zero confirmed colonies of S. sclerotiorum were isolated. This study revealed that Sporecaster worked as designed, but we were unable to properly evaluate the effects of crop rotation on the incidence of S. sclerotiorum apothecia and ascospores because of the lack of disease inoculum.

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Fri Jan 01 00:00:00 UTC 2021