Progress report for ONE24-443
Project Information
We aim to quantify the most effective management strategies that sustainably reduce the impact of white mold on soybeans in Pennsylvania. Participatory on-farm field trials will assess the benefits of selecting shorter-maturity group soybean varieties and using biological seed treatments, paired with unmanned aerial vehicle (UAV) fungicide applications. Using UAVs to apply fungicides will enable spot spraying of white mold hot spots, reducing fungicide use and environmental impact. UAV fungicide application spray coverage will be compared with traditional ground applications in replicated strip trials. The adoption of UAV applications is increasing, yet many questions remain about their use and effectiveness. Soybean growers across Pennsylvania are interested in testing these management strategies due to annual yield losses from white mold. Our farmer partners have expressed interest in participating in these trials, which will use known white mold-infested fields and drone technology. The objectives are i) to determine if a shorter soybean relative maturity group results in lower white mold severity, ii) to test the efficacy of a biological seed treatment against white mold, and iii) to determine if UAV-applied fungicides can effectively minimize the amount of chemical and number of applications needed to manage white mold. Results from these trials will be incorporated into extension talks and handouts. We will conduct soybean grower breakfast meetings to share trial results and highlight more sustainable strategies for controlling white mold in soybeans.
- To determine if a shorter soybean relative maturity group results in lower white mold severity.
- Test the efficacy of biological soybean seed treatment compared to traditional fungicides.
- To determine if UAV-applied fungicides can effectively minimize the amount of chemicals and number of applications needed to manage white mold compared to current practices.
- To communicate results to our farmer partners and other local growers through grower meetings and extension materials.
Hypotheses
- We hypothesize that the use of shorter maturity soybean varieties will decrease white mold disease incidence and severity. In a wet year, with conducive conditions that allow for high levels of white mold development, shorter maturity soybeans will have a short flowering period, reducing the infection window, thus leading to increased yield.
- The Heads Up seed treatment will have a lower disease severity index than the untreated check, but the application of fungicide at R2 will outperform the seed treatment. Application timing is key in white mold management, and we hypothesize that the seed treatment will not sufficient residual activity compared to a well-timed fungicide application.
- Finally, drone application of fungicides will be more effective against white mold because the propellers help to push the product into the soybean canopy to protect flowers better. In particular, the DJI Agras T40 should perform better because its nozzles produce finer droplets for better coverage.
- The Esker Lab and Penn State Field and Forage crop team will present recent white mold disease management data at crop days and other extension meetings. We will provide growers with the best information on cultural, biological, and precision management to more sustainably manage white mold.
Problem
Soybean farmers face numerous diseases that affect plant health and yield. White mold is a fungal disease caused by the pathogen Sclerotinia sclerotiorum. It is the second most yield-limiting disease of soybean in Pennsylvania, causing approximately USD 5.3 million in annual losses (Bandara et al., 2020). The pathogen is a generalist that affects many other crops, including legumes, canola, sunflowers, and weed species.
White mold in soybeans is a difficult pathogen to manage. The overwintering fungal structures, called sclerotia, can survive in the soil for up to 5 years (Heffer Link and Johnson, 2007). Once a grower has white mold in a field, driving the inoculum down to zero is challenging. In addition, spores from the fungal fruiting bodies can travel up to one hundred meters from the point of inoculum (Ben-Yephet and Bitton, 1985). The pathogen also spreads on equipment and gets harvested along with the seed, causing contamination. Weed species that act as hosts of the pathogen can help increase the
inoculum in the soil. S. sclerotiorum prefers cool, humid, wet weather during soybean flowering. These conditions promote disease development during soybean flowering.
Growers with a history of white mold often apply preventive fungicides to protect soybean flowers from fungal spores. Growers commonly applied one or two fungicide applications during the primary soybean flowering period (R1 through R3 growth stages). Because the primary fungicides for white mold are preventive, the presence of symptoms indicates that it is too late to apply them. This presents the problem of growers applying fungicides when environmental conditions do not warrant it, and of applying them across the entire field.
Solution
While management tactics exist for white mold, growers must adopt an integrated management strategy that includes scouting fields to identify hotspots. White mold is not uniformly distributed across a field but tends to be more aggregated in cool, wet spots. The spatial knowledge generated by scouting enables farmers to adopt more site-specific (precision) disease management.
Many IPM practices can help reduce the impact of white mold. Growers can plant shorter-maturity varieties and disease-tolerant varieties. There are no completely resistant soybean varieties, though some are less susceptible. Cultural practices, such as growing a less bushy variety, help open the soybean canopy and prevent wet and humid conditions. Other cultural tactics for management include wider row spacing and lower seeding rates to reduce disease risk. Some biological approaches are available. Growers can spray biological agents, such as Coniothyrium minitans (Contans), to reduce white mold in a field, although the cost and efficacy limit their use.
We hypothesize that integrated disease management that integrates tolerant varieties, shorter maturities, and 30-inch row spacing can reduce the impact of white mold. Despite this, our stakeholders have indicated that applying certain methods to their farm operations may not be feasible. For example, production practices such as lengthening the crop rotation by adding a small grain would reduce viable inoculum in the soil. However, growers who typically do not grow small grains may lack the equipment to implement this practice on their farms. As such, they must rely on other cultural controls, such as variety selection and planting date. Evaluation of different management strategies is crucial for many growers who need assistance to afford investments in other production practices or to avoid reliance on chemical applications. Incorporating several cultural management strategies to control white mold is critical, given the lack of complete varietal resistance.
UAV pesticide application technology is advancing rapidly. Ongoing tests with agricultural drones, such as DJI Agras T40, are being conducted to assess their crop coverage and drift risk (Thompson et al., 2024). The Agras T40 applies chemicals using dual centrifugal atomizing discs rather than the Agras T30's traditional hydraulic Teejet nozzles. Atomizing discs produce finer droplets and are easier to apply variable rates than hydraulic nozzles (Gong et al., 2019). These advancements in spray nozzles may improve coverage and efficiency for controlling white mold in soybeans, given the need to spray flowers lower in the soybean canopy.
Integrating scouting to identify white mold hotspots with drone technology could enable farmers to reduce prophylactic sprays across soybean fields. This has the added advantage of reducing fungicide, chemical, and labor costs, thereby providing the applicator with a safer method (Gibbs et al., 2021; Kim et al., 2023). Precision applications are more manageable with drones, which offer better rate control and easier maneuverability than ground rigs. Pennsylvania’s hilly terrain and diverse soybean field shapes require increased mobility in pesticide applications. Recent advances in drone technology have encouraged farmers to consider their use to make fungicide applications more efficient. During winter meetings in 2024, there has been an increase in inquiries from growers regarding the safety and regulations on drone application of fungicides. Agricultural drone technology is advancing rapidly, and growers need clear, up-to-date information to determine its fit within their farm operations.
Cooperators
- - Producer
- - Producer
Research
2024 and 2025 Annual report notes for the methods:
This is an in-progress report. Beginning in 2024 with our soybean breakfast meetings, we identify farmer cooperators in Cambria, Centre, and Lawrence counties in Pennsylvania. These on-farm trials enabled us to explore questions related to planting date and the use of Heads-Up seed treatments. Each trial had a slightly different focus, but followed our baseline structure as defined in the methods section.
For 2025, we established four on-trials in Centre, Lawrence, and Lebanon Counties. We also had a small plot on-farm trial established in Lebanon County in fields with a known history of white mold (plus a field we have previously mapped to identify potential inoculum densities)
Furthermore, we continue to hold winter breakfast meetings, where results and discussions are shared. One of the topics at many of these locations focuses on our drone work and how to address concerns about soybean white mold.
During Fall 2025 through Winter 2025-2026, we also established a new working group within Penn State Extension focused on the use of drones for agronomic and horticultural crop production and management. Much of this effort was driven by the current project. We expect to share more results in the next report.
More details are provided in corresponding sections regarding results and lessons learned.
Methods as proposed:
Field trials will consist of a randomized strip-trial design with two years of testing. In Centre County, the additional factor will be the soybean relative maturity trial. The additional factor in Cambria County will be the Heads Up biological seed treatment. All three locations (an additional location is in Lawrence County) will incorporate a drone. Please see the attached maps and treatment lists in the Supporting Materials.
At the Centre County location, the maturity group trial will be planted in strips by our farmer cooperator, Mountain Edge Farm, using a split planter with 6 rows planting a 2.6 maturity group variety and the other 6 rows will be 2.8 maturity group. Another planting strip will compare two different 3.3 maturity group varieties (6 rows each) to compare varieties with the same maturity group, but different white mold tolerance ratings. These planted strips will be separated into four plots using bamboo stakes and flags. These plots will each have disease assessments completed, with strips harvested separately. All other production practices will remain the same.
The biological seed treatment trial will be set up using a split planter by our farmer cooperator in Cambria, with half the planter with Heads Up seed treatment and the other half without Heads Up. The rest of the field will be planted using Heads Up. Plots will be set up using bamboo stakes and flags to mark the untreated area. These plots will each have disease assessments completed and be harvested separately. At the R2 growth stage, half of the untreated area will be sprayed with Aproach at 9 ounces per acre, and the remaining will remain the untreated check. If our farmer cooperator has time during planting, he will plant this trial at two different planting dates to address the question of early versus late planting dates on white mold development.
The comparison between UAV and ground rig application methods will take place at all three locations and consist of four treatments. Fields will be planted and follow typical production practices until the R2 growth stage. Treatments will be replicated four times, and the sixteen plots will be sprayed in strips by the drone and the backpack sprayer. Each of the thirty-two plots per location will be 50 feet long. Plots sprayed by the drone will be 27 feet wide, and the backpack-applied plots will be 15 feet. Backpack plots will be sprayed with the CO2 backpack prayer using traditional TeeJetÒ flat fan nozzles. The drone application at the Lawrence County location will be done using a DJI Agras T30 at 3 gallons per acre by our farmer cooperator Rick Telesz. The Centre and Cambria locations will be applied using a DJI Agras T40 at 3 or 6 gallons per acre by Tyler Fleck, a local custom applicator. During fungicide applications, weather data will be recorded, and wind speed and direction will be recorded prior to each treatment.
Fungicide treatments in the application comparison trial will include an untreated check for drone and backpack strips. Treatments will include 9 ounces per acre Aproach at R2 growth stage, 5 ounces per acre Endura at R2, and Aproach at R2 and 10-14 days after. An adjuvant of 0.25% v/v NIS will be used for all applications.
Data Collection
In the seed treatment trial, initial stand counts and Canopeo/Greenseeker data will be collected from the Heads Up-treated and untreated areas. Throughout the growing season, photos will be collected regularly to note the canopy closure across all trials.
Fields will have Sporecaster risk monitored throughout the flowering period to assess disease risk across all trials. Weather data will be collected from Bushel Farm, which provides precipitation and growing degree days from planting. Growth stages will be monitored closely to ensure accurate fungicide applications are made at R2.
At the time of fungicide application, water-sensitive paper will be placed in the middle three rows of each plot receiving a drone or backpack application. SpotOn paper will be used, and the plot number, row number, and height of the paper will be written on the back of the card. Cards will be attached to plot stakes at the appropriate height- 6 inches or 2 feet above ground level. Immediately after the fungicide application, papers will be retrieved and photographed while wearing proper PPE.
Disease assessments will be conducted at the R5 growth stage (beginning seed). Fifty plants in each plot will be assessed on a scale of disease severity between 0 and 3. “0” is no disease; “1” is disease on lateral stems; “2” is disease on the main stem; and “3” is dead plant/pod abortion. The disease severity index percentage will be calculated for each plot.
Harvest
At harvest, plot yields will be weighed using a weigh wagon. Weight will be divided by plot sizes to get pounds per plot. Test weights will be used to calculate the bushels per acre. A subsample from each plot will be collected to test for moisture and test weight. Notes will be made on grain quality based on the number of sclerotia in the seed lot.
Analysis
WSP images will be analyzed using ImageJ, which provides higher-resolution data than the SnapCard app used in the preliminary study. Each image will have the region of interest identified to reduce imperfections (tears, drift, fingerprints, etc.) from being analyzed. ImageJ will identify pixels representing droplets and measure their size and overall coverage on the WSP image. These data will be analyzed to compare application method treatments.
Disease assessment data will also be used to further validate the Sporecaster mobile application for forecasting white mold. The disease assessments for untreated checks in each field will be averaged and compared with Sporecaster risks and weather data to assess the accuracy of the Sporecaster models. Weather data will be summarized and reported for each location to note the general disease pressure.
All disease and yield data will be analyzed using a generalized linear mixed model in R using the lme4 package. Means for each treatment (maturity group, seed treatment, fungicide application method, fungicide product, and possibly planting date) will be compared to untreated checks and separated to determine significant differences among treatments. Data from all location-years will be analyzed together where applicable.
Economic analysis will be completed after year two to determine whether drone application of fungicide is cost-effective compared to traditional ground rig applications. This analysis will evaluate current product costs and custom applicator rates for drone and ground-rig applications. These results will better inform growers about the economic feasibility of drone application of fungicides. The costs and payoffs of fungicide application will be compared with those of other cultural methods, such as seed treatment, maturity group, and planting date.
In 2024 and 2025, the most important factor affecting trial results was the weather. Different combinations of wet and dry periods affected growth an development. As such, individual trial results varied, and factors such as planting date yielded novel findings (e.g., in 2024). Also, our focus was on addressing farmer-centric and localized questions. This focus means that each trial addressed a different aspect of the questions outlined in the objectives and methods. Nonetheless, we have been able to observe several important trends:
- Although the results did not meet our expectations for testing the efficacy of drones in reducing soybean white mold, we did not observe any adverse effects from their use, and we continue to explore how best to improve drone application protocols.
- Farmers continue to question the utility and necessity of drones in soybean production. Winter breakfast meetings have been successful in discussing various technologies and their pros and cons.
- We have leveraged this project and integrated our efforts with those of others in Penn State Extension. The aim is to develop a framework for education, training, and long-term drone technology programs in the Northeast.
2024 Trial Results.
Locations: Cambria, Centre, Lawrence, and Lebanon counties.
General results: Disease severity index was relatively low across the four trial locations. We observed an effect of drone application on late-planted soybeans in Centre County. This location was wet early (during the typical planting periods), dry in June, and then received substantial rainfall for the remainder of the growing season. In this situation, we observed a reduction from moderate white mold levels, with a corresponding yield improvement with the spray. In Cambria County, we also test the use of Heads-Up seed treatment, marketed as a biological seed treatment that can suppress diseases such as white mold. We observed no differences in white mold disease intensity or yield in this trial. Further trial work is warranted under more favorable conditions.
2025 Trial Results.
Locations: Centre, Lawrence, and Lebanon counties.
General results: A combination of large strip and small plot on-farm trials was established in 2025. Dry weather throughout much of the growing season reduced the intensity of white mold disease. Overall, large strip trials showed no differences in disease intensity for white mold or in yield. Small-plot trials in a field previously mapped for white mold and the pathogen showed that all treatments reduced white mold disease severity index, even though the trial had low-to-moderate disease intensity. Yield trends were observed in this trial, but no statistically significant differences were noted. These trends are an important finding as we continue to explore the scenarios in which drones may be most effective. In this situation, understanding the spatial distribution of white mold at the larger field scale is vital to translating that knowledge into spray maps that emphasize where risk is highest. Furthermore, yields at several locations were lower than those we typically observe, according to discussions with our farmer cooperators. Although still high relative to statewide averages, these locations often have the highest yield potential in Pennsylvania.
Extension and outreach.
We leverage this project with another one funded by the Pennsylvania Soybean Board to facilitate our winter breakfast meetings. During 2024-2025, we hosted seven meetings across Pennsylvania. White mold and drone technology have been incorporated into discussions, particularly to consider the value-added aspects of drone technology beyond white mold management. For example, one of our farmer cooperators (a father-and-son team) will purchase a drone and obtain training and certification. They see this as a valuable component of their farm operations, particularly to improve the timeliness of production and management applications. These goals align with our cooperator in Lawrence County, who emphasized the value of being able to perform farm operations at their convenience.
In late 2025, we also began discussions with members of the Agronomy, Horticulture, Pest Ed, and Farm Safety Teams, through Penn State Extension, regarding the use of drones for crop production and management. There is recognition that we need to develop an internal (professional development) and external educational program. We will continue these efforts as part of our 2026 program.
Looking Ahead to 2026.
Our goals for this year include: (1) establishing additional trials to continue to explore the year-to-year variation in white mold risk; (2) explore combined analyses in our current trial database; (3) leverage our current effort to expand further our extension team efforts (internal and external) regarding the effective use of drone technology; and (4) develop a draft best management recommendations for using drones for white mold of soybean in the Northeast.
To date, results have been variable regarding the use of drones to apply fungicides for the management of white mold of soybeans. The weather has been the primary driver of reduced disease incidence. Small-plot trials further confirm the need for spatially explicit information at the field scale to improve efficacy in disease control, yield, and economics. Nonetheless, these efforts have yielded substantial value, as we have learned from our farmer cooperators that they are exploring the purchase of drones to improve their overall farm operations. Furthermore, our efforts have positioned our team as leaders within Penn State Extension in developing new programs for both internal training (professional development) and external education.
Education & outreach activities and participation summary
Participation summary:
This proposal includes funding to host two breakfast meetings with our cooperators. The 2023 growing season was one of the worst years for white mold incidence in Central PA. Therefore, many growers have an interest in learning new management strategies for white mold. The small breakfast meeting style has allowed the best conversation between growers and researchers to receive valuable feedback and grower needs. With just a few growers participating, growers tend to be more open about their production practices and disease management on their farms. This project includes ideas from our farmer partners, and we want to provide trial organization and data collection to measure differences among the treatments they suggested. We have already established good relationships with these farmer partners, and we want to continue to get feedback on our research so they can improve their disease management practices and bottom lines.
These discussion meetings will be conducted at local cooperative extension buildings or restaurants. Since growers tend to be available during breakfast or lunch, a meal will be provided to those who participate. During the meetings, our team will present results from the previous year’s trial, and participants will have the opportunity to ask questions and voice comments and concerns about the research. Grower discussion meetings will be conducted using open-ended questions to determine their priorities and needs in future research projects. The meeting will focus on growers’ perspectives on white mold incidence and risk, and white mold management strategies will be evaluated against each grower's situation.
Beyond our partner farmers, this project will produce data relevant to soybean growers across Pennsylvania, and results will be shared at various extension meetings and Penn State crops days. Growers are often presented with various data about the effectiveness of fungicides and new UAV technologies. We need to provide unbiased third-party results they can trust to determine which management tactics to use. Using our trial data, our extension team has developed presentations on white mold in soybeans over the past several years. These results are shared with the entire Penn State Field and Forage crop team to be disseminated across the state. This research is valuable for informing growers about the latest management techniques from year-to-year.
Learning Outcomes
Farmer cooperators: Importance of understanding how drones may or may not fit into their operation. This includes consideration by one of our cooperators to purchase a drone and have his son (father-son team) obtain certification and the necessary licenses to be a drone pilot and applicator.
Extension impact: Leveraged research and outreach efforts have led to the development of a core team within Penn State Extension to expand drone education and training. This also includes internal programming and programming for our core stakeholders. We expect these efforts and their corresponding impacts to increase in 2026.