Current Situation:
Red crown rot (RCR) is a new soilborne fungal disease of soybeans in Illinois, and last year, infected fields suffered an approximate 25 bu A-1 yield loss (see supplement, ISA webinar). This disease historically has only been an issue in peanut/cotton/soybean rotations in the Deep South. RCR produces symptoms very similar to sudden death syndrome (SDS), and can be easily misidentified as SDS if not properly diagnosed. Consequently, our knowledge of the
distribution of this pathogen in Illinois is unknown as it may have been misidentified as SDS in some areas. No resistance to RCR is available in soybean cultivars. Furthermore, the efficacy of fungicide active ingredients and utility of fungicide seed treatments for managing the Illinois RCR pathogen is unknown. To date, RCR has not been detected in any other Midwest or great lakes states.
Approach:
We will work with entities such as UIUC Extension, the Illinois Certified Crop Advisors, Growmark, and ISA to establish a collaborative network to survey soybeans throughout the state for RCR. Fields with interveinal chlorosis starting at the reproductive stage in growth will be targeted for sampling. Plant samples will be acquired at R5/R6 from each field, and sent to the Kleczewski lab, where they will be processed for presence of the pathogen following established protocols. A second season of the survey will be beneficial, as environmental conditions can mask disease symptoms from year to year, and fields infested with the pathogen may not be planted to soybeans during the first season. A distribution map will then be generated and published on the ISA website, the Illinois Field Crop Pathology Website, and print copies
developed and made available to clientele at outreach meetings and events.
The Kleczewski lab has 8 isolates of the RCR pathogen collected from the 2018 crop. We will screen at least 7 commonly used fungicide active ingredients for activity against these isolates in the laboratory using a poison plate assay. Each isolate x fungicide a.i. combination will be replicated at least twice and the experiment replicated twice. Data will be statistically analyzed, and shared with clientele and industry at extension outreach meetings. Data will also
be published in a peer-reviewed journal for posterity and to validate the results.
Industry representatives will be contacted and asked to provide soybean seed treatments commonly used in Illinois, as well as new or upcoming seed treatments that have not been assessed for efficacy for managing RCR. Seed treatments will be screened in the lab and greenhouse for their ability to minimize pre- and post-emergent damping off (i.e. germination) caused by the Illinois RCR pathogen. Seed treatments will also be assessed for efficacy in mitigating foliar symptoms and protecting yield using an inoculated small plot trial at the UIUC plant disease farm. Plots will be irrigated to ensure adequate wetness and infection. A second small plot experiment will be conducted near Pittsfield, Illinois in a field with a history of severe RCR. Disease and yield data will be collected. All trials will be replicated and randomized, and data statistically analyzed. As environmental conditions may not be favorable at every site every season, a second year of field trials would help ensure that sufficient disease is present to adequately justify our conclusions. Data will be summarized and published at ISA and UIUC outreach venues as described previously. At least one field day held at UIUC plant disease farm will include this project. A webinar on RCR in Illinois will be developed and presented through
ISA and UIUC, and a factsheet on RCR published in the Crop Protection Network.