Proposed Methods/Tactics
A graduate student will be recruited to lead these projects as part of her MS.C program. The student will work with industry, producer, and extension partners to collect FLS infected soybean tissue from across the state. In addition, fields will be surveyed in underrepresented areas of the state, for example central and Northeast Illinois. Samples will be placed in plastic bags on ice, and shipped to the UIUC pathology lab. Spores of C. sojina will be identified with the aid of a hand lens and single spore isolations carried out onto soybean/lima bean agar [3]. If no spores are present, sporulation will be induced using humidity chambers. Poison plate assays will be used to assess the sensitivity of individual isolates to technical grade pyraclostrobin, azoxystrobin, fluopyram, fluxapyroxad, solatenol, and other new SDHI active ingredients as determined by industry colleagues and availability. The values at which 50% of sporulation and growth is reduced relative to unamended controls will be determined using standard curve fitting procedures

[9-12]. Samples will be collected from at least 25 locations and a minimum of 50 isolates collected from samples. We will focus on fields with severe FLS or fields where fungicide applications have been made but the disease is present as these have a greater likelihood of having elevated fungicide resistant populations.

We will establish 5-8 locations throughout Illinois in 2021 to assess the impacts of cultivar resistance and fungicide on the likelihood for a particular management strategy to pay. Locations will be established on research and grower farms, in fields with a recent history of FLS. Two cultivars (one resistant, one susceptible to FLS) will be planted at each location in small plots, following our standard protocols. Efforts to plant into continuous soybean will be made, as the focus on this work will be fungicide and cultivar interactions. Cultivars will be overlaid with a fungicide treatment targeting FLS. Treatments will include a non treated check, Delaro, Veltyma, Lucento, Miravis Top, Aframe Plus, Domark, and Tilt applied at 15gpa over the inner 5ft of plots using a backpack C02 sprayer equipped with 4, Teejet 80v02 nozzles. All products will be applied with 0.250% NIS. These products represent a mix of newer “premium” products and an older, or generic cheaper fungicides, allowing us to calculate profitability indices over a larger range of price points. Additional fungicides could be added, but at the sacrifice of varieties. Each treatment will be replicated 4 times at each site, resulting in 64 plots per site and 384 plots in the season. In order to generate sufficient data for probability analysis, and to ensure a wide range of environmental conditions to broaden inference, a second year of data will be required.

The percent foliar severity for frogeye leaf spot will be assessed for all plots at V5/6, R3, and R5, and the aeea under the disease progress curve determined [13]. Although FLS will be the focus, other diseases will be rated if present. Yield for each plot will be obtained with a Masset 8xP small plot combine, and yields adjusted for population. Subsamples of seed will be collected and rated for infection by C. sojina, which can infect pods and seeds later in the season. Confirmation for C. sojina as the agent of discoloration will be made by surface sterilizing seeds, isolating fungi in standard media, and sequencing the ITS region of the fungal genome following standard lab protocols [14]. Surveys of industry and producers will be used to establish average application costs for the three fungicides used in this work. These values, as well as yields, will be used to determine the probability of a particular program to produce sufficient yields improvements to pay for product application and deductions due to potential grain quality issues following established metaanalytical methods

[15-17]. In addition, the probability of a given practice reducing FLS to a specified amount will be assessed. Exploration of this dataset will potentially enable us to approximate potential disease thresholds for FLS in Illinois soybeans. However, two seasons of data will be needed to produce sufficient data to conduct these analyses and ensure adequate environmental diversity.

Communication of Impact

Data will be summarized and published at ISA and UIUC outreach venues as described previously. A preliminary profitability calculator could be developed with at least two years of data, which may potentially lend itself to additional work to provide a profitability calculator for soybean foliar fungicides in Illinois in future years. Project information will be provided by the graduate student at university field days. The student will present data at either the North Central APS meeting or APS national meeting in 2022. A webinar on FLS and fungicide resistance in Illinois will be developed and presented through ISA and UIUC, and a factsheet on FLS and fungicide resistance developed. Results will be shared at UIUC Extension certified crop master sessions, industry meetings, the UIUC ag day, and online venues and webinars. Results will be presented by both PI Kleczewski and the MS student, depending on the venue. The student will be responsible for developing all extension materials and conducting all aspects of this work.

Results will be published in peer-reviewed scientific journals and presented at scientific meetings such as APS. ISA will be credited in all publications and presentations.

Lastly, in order to assess knowledge gained and utility of deliverables, pre and post surveys will be conducted when possible at webinars and in person meetings. Data will be shared with ISA. Data will be shared with ISA.


Timeline:

Quarter One activities: Begin planning 2021 field season. Request seed and chemical treatments. Locate collaborators to help identify locations and collect samples.
Quarter Two activities: Plant locations, rate and treat all locations. Start to collect FLS isolates.
Quarter Three activities: Harvest all plots purify all FLS isolates. Begin fungicide sensitivity assays.
Quarter Four activities: analyze all data and provide year one report to ISA and at extension events during winter.