The Basics About Drones for Fungicide Application

INSIGHTS

• Drone spraying can be a valuable option in areas where ground or aerial application is either cumbersome or not feasible.

• Agronomy in Action Research team found no difference in corn yield response between drone and ground fungicide application.

• There are several variables (e.g., cost, FAA requirements, etc.) that must be considered when evaluating whether to invest in a drone sprayer.

Introduction

Adoption of drones in agriculture continues to rise. Initially, most utilization was for field scouting. However, usage for pesticide application continues to rise. Multiple years of Agronomy In Action Research trials have demonstrated the value of R1 fungicide application in corn, even when disease pressure is low. Initially, nearly all applications were made using large scale aerial or high clearance sprayer equipment. However, as drone- specific spraying technologies continue to develop, and affordability improves, grower interest in purchasing and operating drones for pesticide application is growing. As adoption continues, there are still many questions about the effectiveness of spray applications as compared to traditional methods. This article discusses the basics of fungicide application by drones and how it compares to its traditional ground-based counterpart.

Spray Drone Basics

Exact spray width and capacity of spray drones varies by manufacturer, though spray patterns up to 35 feet and 10- gallon tank capacities are most common. Initial spray drones were equipped with booms (Figure 1). However, this design will likely decrease in popularity going forward due to less consistent spray coverage and drift potential.¹ New spray drones are now generally equipped with a boomless controlled droplet atomizer system (Figure 2), where spray droplets are produced by the rotational speed of a cup.² This creates more consistent droplet sizes compared to a range of droplet sizes that are produced by fan spray tips.

Figure 1. Example of a boomed spray drone equipped with flat fan nozzles.

A key difference between drone and traditional sprayers is spray volume. Most pesticides labeled for aerial application require rates of at least 2.0 gal/A, meaning maximum coverage area for a 10-gal spray drone tank would be five acres. Although the carrier volume is significantly less than other traditional methods, academic research has found that it produced more consistent vertical coverage within the canopy.³ Additional academic research has also shown that fungicide application by a drone was effective against foliar diseases. In Kentucky, Trivapro^® fungicide (13.7 oz/A rate) reduced grey leaf spot severity at three sites and increased grain yield by 4.4% (9.1 bu/A).⁴

Figure 2. Example of a boomless spray drone equipped with a controlled droplet atomizer system.

Trials Comparing Application Methods

Graph 1. Response of corn yield to fungicide application method at Slater, IA, in 2019 (left) and Waterloo, NE, in 2023 (right).

Agronomy in Action Research trials were conducted at Slater, IA, in 2019 and Waterloo, NE, in 2023 to assess the effectiveness of spray drone fungicide application on corn grain yield (Figure 3), and how it compared to ground application. Fungicide (Trivapro in 2019; Miravis^® Neo in 2023) was applied at R1 to multiple Golden Harvest^® corn hybrids (36 in 2019 and 2 in 2023). The drone application consisted of a carrier rate of ≤3 gal/A (3.0 in 2019, 2.0 in 2023) applied approximately 10-feet above the crop canopy. Ground application consisted of a rate of 20 and 15 gal/A in 2019 and 2023, respectively.

Yield increases of 5.0 and 5.8 bu/A were observed in 2019 and 2023, respectively when fungicide was applied with a spray drone compared to the untreated control (Graph 1). No significant foliar diseases were present in the untreated checks at or after the time of application, suggesting the yield response was likely driven more from plant health benefits of azoxystrobin + SOLATENOL^® fungicides within Trivapro and azoxystrobin + ADEPIDYN^® fungicides within Miravis Neo.

Although ground applications were 2.8 bu/A greater than drone applications in 2019, differences were not statistically significant. Ground and drone application method yields were similar in 2023, indicating both application methods were equally effective delivering active ingredients with systemic activity. Improvements in nozzles utilizing droplet atomization systems in 2023 likely improved drone performance over flat fan nozzles used in 2019. Research under high disease pressure is needed to assess how non-systemic contact fungicides perform when applied with drone sprayers.

Where Do Spray Drones Fit?

Drone sprayers are not meant to replace traditional ground or aerial options, although there are situations where they may have a better fit:

1. Field conditions do not allow for ground equipment traffic.

2. Small or irregularly shaped fields.

3. Uneven terrain (e.g., terraces, draws)

4. Areas or gaps missed by traditional application.

5. Fields where off-target movement poses a risk (e.g., near residential areas or vineyards).

Figure 3. Drone fungicide application over corn.

Drone spraying also creates an opportunity for site-specific pest management. For example, if field scouting identifies pockets within a field where insect or disease pressure has reached an economic threshold, drone spraying could be utilized to target application only in those areas, thus reducing overall cost (when compared to a blanket application across the entire field).

Important Considerations

Besides equipment cost, there are several other factors to consider when evaluating drone spraying:

1. Application efficiency: Because of the limited swath path and tank capacity, application efficiency is limited (<50 A/hour). In addition, battery life is relatively short (typically under 15 minutes, depending on weather conditions), also requiring frequent changes and charging.

2. Regulations: Drones used for non-recreational use require FAA Part 107 (Certified Remote Pilot) and 137 (Dispensing Chemicals and Agricultural Products with UAS) certifications. The drone plus cargo cannot exceed 55 lbs (unless an exception is granted).

3. Pesticide applicator licensing: State or local certification for aerial application of pesticides may be required.

4. Product label: Most labels currently do not provide restrictions with drone application because they are generally captured within aerial application restrictions at the time this article was written.

5. Insurability: Most general farm policies do not cover drones, so a separate policy may be necessary.

Summary

Fungicide application with drones has a fit in areas where traditional application via ground or aerial application is not feasible or is cumbersome. It can also potentially reduce input costs in fields where only targeted fungicide application is needed. There are significant factors that must be weighed when assessing the decision to adopt this application method. However, the capabilities would complement any disease management program.

Reference

¹ Okzan, E. 2023. Drones for spraying pesticides – opportunities and challenges. Ohio State Univ. https://ohioline.osu.edu/factsheet/fabe-540

² Kness, A. and E. Crowl. 2020. Evaluating efficacy of aerial spray applications using drones. Univ. of Maryland. https://blog.umd.edu/agronomynews/2020/11/10/evaluating-efficacy-of-aerial-spray-applications-using-drones/

³ Fulton, J., A. Leininger, and C. Lee. 2023. Fungicide application in con with ground machines and spray drones. Ohio State Univ. https://ocj.com/2023/03/fungicide-application-in-corn-with-ground-machines-and-spray-drones/

⁴ Wise, K., N. Roy, P. Hardesty, R. Arnett. 2021. Drone fungicide applications in corn. Univ. of Kentucky. https://plantpathology.ca.uky.edu/files/ppfs-ag-c-11.pdf

⁵ Wang, G., Y. Han, X. Li, J. Andaloro, P. Chen, W.C. Hoffmann, X. Han, S. Chen, and Y. Lan. 2020. Field evaluation of spray drift and environmental impact using an agricultural unmanned aerial vehicle (UAV) sprayer. Science of the Total Environment. https://www.sciencedirect.com/science/article/abs/pii/S0048969720333131#f0005