Final report for ONC24-142
Project Information
Unnecessary fungicide applications affect our ability to sustainably manage crop diseases. They provide opportunity for fungal pathogens to develop fungicide resistance due to routine chemical exposures. We need to conserve our use of fungicides now, so that products are available in the future as disease pressure is predicted to increase with a changing climate. Loss of fungicides will increase our reliance on techniques like tillage to bury diseased crop residue.
The recent emergence of two corn diseases in the north central US has led to even more concern about stewardship of fungicides. Tar spot and southern rust of corn can reduce yields by 45 to 50 bushels per acre in certain conditions. In 2023, some farmers in northwest Missouri chose to make three fungicide applications to manage tar spot. Success of those applications in protecting yield remains unknown. The general lack of information to assist these farmers and others in making application decisions can be addressed through on-farm strip trials.
The proposed partnership will allow University of Missouri Extension Specialists and Missouri farmers to compare single and multiple fungicide applications to corn. Reducing unnecessary fungicide use is an important component of sustainable integrated disease management.
We plan to carry out on-farm strip trials to provide information on economic and sustainability benefits (and costs) of multiple fungicide applications to corn. We will utilize the following types of data for this analysis:
- Agronomic input data like seeding rate, row spacing, irrigation, total number of active ingredients in products, growth stage at application
- Economic input costs for products and application
- Environmental data, such as topography and weather
- Yield data
Findings generated from this study will be applicable to farmers and agriculture professionals in the north central region and to technical audiences working to find sustainable disease management solutions.
Cooperators
- - Technical Advisor (Researcher)
Research
On-Farm Trial Locations: During the summers of 2024 and 2025, 15 on-farm research trials were initiated in cornfields across 15 Missouri counties. Trial locations included both river-bottom fields (adjacent to the Mississippi or Missouri Rivers) and non-irrigated upland fields to capture regional environmental conditions. Of the 15 sites, 13 were successfully completed and analyzed. Two trials were excluded: one due to logistical constraints that prevented aerial fungicide application at the VT/R1 growth stage, and a second due to data loss from GPS interference during harvest.
Fungicide Treatments and Application Timing: Each location included a blanket application across the field at the tasseling/silking growth stage (VT/R1) with the producer's preferred commercial product. The second application, both product and timing, were determined by the producer's preference. One producer opted for an early vegetative application (near the V5 stage), while the remaining producers chose a late-season application 3 to 4 weeks post-VT/R1.
Experimental Design and Plot Dimensions: The second fungicide application was carried out using either a strip-trial layout or randomized complete block design (RCBD), which was adapted to field dimensions and equipment limitations. All late-season applications were applied via an unmanned aerial vehicle (UAV/drone) with a delivery volume of 2 gallons per acre (GPA) at a height of approximately 11 feet above the canopy. To account for variability across the field, treatments were mapped in advance using topography data and farmer's knowledge of yield history to minimize effects of the environment. Specific plot measurements were:
- Plot Width:40 to 120 feet (matched to commercial field layout and combine harvester header widths).
- Plot Length:300 to 500 feet.
- Replication:5 to 7 replications per site, depending on total field size.
Data Collection
Disease Assessment: Disease severity was assessed by estimating the percentage of symptomatic leaf area on five representative plants per treatment. A minimum of 25 plants were rated for the 1-pass control and 25 plants for the 2-pass treatments per trial. The ear leaf, the leaf immediately above the ear leaf, and the second leaf above the ear leaf were evaluated for southern rust (Puccinia polysora) and tar spot (Phyllachora maydis).
Agronomic and Harvest Data: Late-season lodging were recorded as percentages based on the push test of 10 plants per plot. Yield data were obtained via combine yield monitors
Disease Severity
Across the evaluated environments, the 2-pass fungicide program consistently reduced foliar disease severity compared to the 1-pass application when evaluated at the R4/R5 growth stage.
- High-Pressure Environments: Severe disease pressure, defined as greater than 5% of the ear leaf covered in lesions, occurred at two sites. At the site evaluating an early application, the sequential V4/V5 followed by VT/R1 treatment, reduced ear leaf disease severity from 5% (1-pass) to 2% (2-pass). At the second high-pressure site, the 2-pass program, a VT/R1 application followed by a 21 days post-VT/R1 application, reduced disease severity substantially from 11% in the 1-pass to 1% in the 2-pass program.
- Low-Pressure Environments: At the remaining locations, disease pressure was very low(less than 5% ear leaf coverage). Even under low pressure, the sequential 2-pass treatment consistently minimized visible symptoms from 0.8% in the 1-pass plots to 0.4% in the 2-pass plots.
Lodging
Lodging incidence was minimal across locations, with no distinct differences observed between the 1-pass and 2-pass fungicide programs.
Grain Yield and Return on Investment
Yields generally trended higher in the 2-pass application compared to the 1-pass control, with yield difference ranging from 1 to 3 bushels per acre depending on local disease pressure. These minor yield differences were not statistically significant. 2026_FieldDay Handout
To evaluate the economic feasibility of a multi-pass strategy, return on investment (ROI) was calculated based on a market corn price of $4.50 per bushel against two input cost scenarios:
- Standard Fungicide Program: Based on a total application cost of $35.00 per acre ($25.00 for a premium fungicide product and $10.00 for the aerial application), a yield increase of 7.8 bushels per acre is required to break even on each fungicide pass.
- Low-Cost Fungicide Alternative: If a less expensive product is utilized at $15.00 per acre (bringing the total application cost to $25.00 per acre), the break-even threshold drops to approximately 5.6 bushels per acre.
While these on-farm trials demonstrated that a 2-pass fungicide program can reduce foliar disease severity, the reduction in disease did not translate into a sufficient yield response (1 to 3 bushels per acre) to cover input costs for a second application.
Outreach and Extension Impact
These findings are actively being disseminated to producers and industry stakeholders across Missouri to guide data-driven input decisions.
Additionally, project investigators have partnered with the Missouri Corn Growers Association to build upon this data and conducting additional projects to optimize the most cost-effective 1-pass fungicide application timing for regional corn production.
Educational & Outreach Activities
Participation summary:
Completed Outreach and Presentations:
Conferences and Trainings: Presented project findings at the MU Crop Management Conference (2024, 2025), the Commercial Pesticide Applicator Training (2025, 2026), and the Illinois Certified Crop Advisors Conference.
Regional Engagement: Shared data through winter meetings, local field days across Missouri, and teleconferences with regional extension agronomy specialists.
Academic Recognition: Graduate student Hailey Emanuel presented project data at the 2026 North Central American Phytopathological Society (APS) meeting and earned second place in the student presentation competition.
In-Progress and Upcoming Activities:
Publications:Hailey is currently finalizing data analysis to conclude her master’s thesis and is drafting a peer-reviewed manuscript for submission.
Future Outreach:We plan to continue disseminating these results throughout the rest of the 2026 growing season and during the upcoming 2026–2027 winter meeting circuit.
Learning Outcomes
Survey feedback at winter meetings and the Crop Management Conferences indicates that farmers would reconsider their approaches to managing tar spot, specifically, as it relates to tar spot of corn.
Project Outcomes
Economic Outcomes
The economic viability of the 1-pass fungicide application was demonstrated under real-world, commercial stresses, due to the engagement of farmer partners. Participating farmers dedicated acreage to test the fungicide applications against their standard calendar-based spray schedules and were involved in coordinating the VT/R1 fungicide application, product selection, and second pass timing. This direct partnership allowed us to track yields across a range of farm management styles and microclimates. The partnership demonstrated that eliminating one fungicide application improved the net return per acre by reducing inputs without sacrificing yield and equips Certified Crop Advisors (CCAs) and agronomists with concrete, localized data.
Environmental Outcomes
Reducing chemical footprint of modern crop protection requires strategies that work at a landscape scale. Over-applying fungicides accelerates chemical resistance among target pathogens. The partnership successfully demonstrated that a reduced localized chemical load can lead to similar disease suppression and yield protection. Reducing the chemical input in turn reduces the risk of non-target chemical exposure in the environment.
Social Outcomes
Farmers trust other farmers. Growers who partnered in this research serve as the best advocates to carry the message forward. By sharing their firsthand experiences, they can accelerate the regional trust and adoption of these practices going forward.
One example of the project's real-world impact involves a long-time row-crop farmer from central Missouri. Historically, this producer relied on a standard, calendar-based schedule that automatically included a second-pass fungicide application as an insurance policy against southern rust and tar spot.
Through his partnership with our project, the grower saw the data from his own acreage, and it demonstrated that the decrease in disease severity from the second pass did not correspond to added yield protection. This research has shifted his mindset and made him mindful of skipping a second application.