1. Validation, Optimization, and Deployment of Fungicide Advisories for Soybean Virginia Soybean Board 2014 Project Report & 2015 Project Proposal Dr. Hillary L. Mehl, Plant Pathologist Dr. David Holshouser, Soybean Agronomist Tian Zhou, MS Student Virginia Tech Tidewater AREC March 12, 2015

2. Integrated Disease Management - Soybean Know your target disease so you can select the best cultivar and fungicide – foliar fungi Plant resistant/tolerant cultivars (or be aware of susceptibility to specific diseases) Optimize fungicide timing and chemistry for target disease

3. Do Foliar Fungicides Pay? Points to Consider How susceptible or resistant is your cultivar? Yield potential – what are you protecting? Crop growth stage and timing of fungicide applications Previous crop and cropping system (e.g. no till) Disease pressure Weather

4. 2014 Objectives 1.Validate and optimize a weather-based disease advisory model for timing of foliar fungicide application in soybean 2.Evaluate profitability of different fungicide spray schedules based on yield response and input costs 3.Initiate development of a web-based disease advisory alert system for soybean

5. Fungicide Spray Window Growth stage-based fungicide applications

6. Foliar disease risk model: “Favorable days” for disease development

7. Soybean Weather-Based Fungicide Advisory: Validation Trials 2014 Eastern Virginia AREC (Warsaw) Tidewater AREC (Suffolk) 7 on-farm trials 2 small plot studies (ARECs) Weather station Treatments

8. Fungicide timing vs yield response Single application Multiple applications Each % yield response = 0.6 bu/A TAREC (Suffolk) – Cercospora blight *Weather advisory and growth stage- based sprays were made on the same date EVAREC (Warsaw) – Frogeye leaf spot

9. CountyVarietyTreatment Spray DateFungicide & RateYield (bu/A) OrangeAsgrow AG4633ControlNA 47.4 B R3July 29Priaxor - 4 oz/A52.6 A Decision AidAug 4Priaxor - 4 oz/A52.0 A CulpeperNK S41-J6ControlNA 61.0 A R3Aug 11Priaxor – 4 oz/A59.7 A Decision AidAug 20Priaxor – 4 oz/A57.2 A StaffordPioneer P39T67ControlNA 67.8 A R3Aug 7Quadris Top - 11 oz/A69.7 A Decision AidAug 16Quadris Top - 11 oz/A70.2 A AmeliaArmor 5363ControlNA 41.4 C R3Aug 15Quadris Top – 10 oz/A47.7 A Decision AidAug 20Quadris Top – 10 oz/A46.1 B Nottoway ControlNA 45.4 B R3Sept 16 46.7 A Decision AidSept 26 46.7 A SussexHubner H53-12R2ControlNA 30.0 B R3Sept 3Stratego YLD – 6 oz/A34.2 A Decision Aid Sept 16 (Sept 9)Stratego YLD – 6 oz/A32.7 A AccomackChannel 4206ControlNA 54.7 A & 4306R3Sept 11Stratego YLD – 4 oz/A53.6 A Decision AidSept 15Stratego YLD – 4 oz/A48.8 A

10. “Favorable days” vs yield response +4-6 bu/A

11. Yield response needed to offset cost of fungicide application in soybean Treatment cost/A Soybean price/bu $9$10$11$12$13$14 $15.001.71.51.41.31.21.1 $17.501.91.81.61.51.3 $20.002.22.01.81.71.51.4 $22.502.52.32.01.91.71.6 $25.002.82.52.32.11.91.8 $27.503.12.82.52.32.12.0 $30.003.33.02.72.52.32.1 $32.503.63.33.02.72.52.3 $35.003.93.53.22.92.72.5 Favorable days for disease development: < 8 days after R3  4-6 bu/A yield response > 8 days after R3  1-2 bu/A yield response (or less)

12. Virginia Ag Pest and Crop Advisory Blog http://blogs.ext.vt.edu/ag-pest-advisory/ The weather-based advisory needs to be further validated, but preliminary fungicide advisories for soybean will be posted on the Virginia Ag Pest and Crop Advisory Blog in 2015.

13. Collection of weather data Hourly weather data are needed to run model for advisory Currently using weather stations at a limited number of locations Considering a weather data service ($100-$200 per site per year)

14. 2014 Conclusions Fungicide applications are more likely to result in a significant yield response if favorable conditions for disease development occur within 7 days of the R3 stage. Fungicide applications made when weather conditions are favorable for disease development are likely to be profitable. Additional years of data including ranges of environmental conditions and detailed assessments of crop and disease development are needed.

15. 2015 Objectives 1.Validate and optimize a weather-based disease advisory for foliar fungicide application in soybean 2.Survey soybean fields for fungicide resistant pathogens

16. Objective 1: Validate and optimize weather-based disease advisory Collect second year of data to validate and optimize weather-based parameters for timing fungicide applications Repeat small-plot and on-farm trials comparing growth stage and weather-based fungicide applications Collect more detailed information on disease and crop development over time

17. Objective 2: Survey soybean fields for fungicide resistant pathogens Control/management Resistant cultivars (best) Rotate out of soybean Foliar fungicides Generally not a problem in VA High severity in some fields in 2013 & 2014 (defoliation) Potential for up to 30% yield loss in some fields Frogeye leaf spot (FLS) Causal agent = Cercospora sojina

18. Virginia - fungicide resistant isolates of FLS confirmed in 2 out of 4 fields sampled in 2014 Strobilurin resistant frogeye leaf spot

19. Fungicide Resistance Quinone outside inhibitors (QoIs)/strobilurins are highly effective, broad-spectrum fungicides BUT fungicide resistance can occur rapidly within pathogen populations leading to disease control failures

20. Inhibit mitochondrial respiration of fungi by binding to cytochrome bc1 enzyme complex at Qo site (site specific mode of action) G193A mutation: Glycine  Alanine at codon 143 (complete resistance) Single base change in DNA sequence: GGT  GCT Sensitive Resistant DNA sequence from cytochrome b gene in Cercospora sojina (frogeye leaf spot fungus) Strobilurin / QoI fungicides

21. A DNA-based assay can be used to identify strobilurin resistant FLS Fungal isolate or infected plant tissue Extract DNA Amplify DNA by PCR (target sequence conferring sensitivity / resistance to strobilurin fungicides) Visualize DNA (PCR product) on agarose gel Resistance mutation Wild-type (sensitive) Determine frequency and distribution of strobilurin resistant FLS in Virginia

22. Why Monitor Resistance? Resistance  control failures  crop losses Use of ineffective fungicides may increase resistant strains of fungi

23. Fungicide trade name Fungicide common name Fungicide class* Production rate per acre Quilt Xcel azoxystrobin + propiconazole strobilurin + triazole 14.0 ‑ 21.0 fl oz Quadris TOP azoxystrobin + difenoconazole strobilurin + triazole 8.0 ‑ 14.0 fl oz Stratego YLD trifloxystrobin + prothioconazole strobilurin + triazole 4.0-4.65 fl oz Priaxor pyraclostrobin + fluxapyroxad strobilurin + carboxamide 4.0-8.0 fl oz Aproach Primapicoxystrobin cyproconazole strobilurin + triazole5.0-6.8 fl oz Pre-mix fungicides are recommended for fungicide resistance management. However, if strobilurin resistance becomes widespread in Virginia, different fungicide modes of action or rates may need to be recommended. Fungicides Pre-mixes for Resistance Management

24. 2015 Budget Request ItemAmount requested Graduate student (100%) Salary $ 22,021 Fringe benefits $ 1,486 Wage employee Salary (2 months) $ 4,000 Fringe benefits $ 310 Materials/supplies $ 2,000 TOTAL $ 29,817

25. Questions?