Drone Spraying: The Progress, Pitfalls, and Path Forward

The below X post includes a video illustrating the risks of poorly operated drone applications — in this instance, fungicide specifically.

On X throughout the 2025 season there have been images and videos conveying the inconsistency of drone swaths, specifically for quadcopters/rotary wing type drones (eg: DJI Agras T50) one of the major constraints of these kinds of drones moving from niche and spot spray focused to viable as a system for larger scale row crop farming.

The X posts are anecdotal, but the main point is that operator margin for error grows drastically when moving from ground sprayer to rotary/quadcopter type spray systems.

A few things to consider.

Note: I am expiclitly looking at rotary/quadcopter systems in the below.

Swath width and coverage consistency

The main problem comes back to swath width and spray coverage: with ground sprayers you know your swath. A 120-foot ground sprayer boom delivers essentially 120 feet under most conditions.

With rotary drones, swath width can be variable and unpredictable.

In one study highlighted in The Western Producer, a drone flying 3m above ground at ~30 km/h (~18.5 mph) and delivering 3 gallons/ac produced varying swaths:

• 21 ft swath

• 23 ft swath (30 minutes later)

• 16 ft swath (another 30 minutes later)

That’s a 25–30% swing in width within hours, producing striping from overlap and misses. Even great operators may struggle navigating settings and controls to account for subtle variations in temperature, humidity or wind that influence droplet deposition.

Multiple factors influence this inconsistency: flight height, speed, wind, rotor downwash, nozzle type, and even terrain undulation.

One study with a DJI T10 confirmed that:

• Higher altitude (4m vs 2–3 m) widens swath but increases drift.

• Lower volumes (1 US gal/ac) narrow swath and sometimes improved uniformity.

• Nozzle type changes distribution: very coarse droplets concentrate deposition in the center, finer droplets spread more, but then become higher risk to drift.

Every combination of conditions can produce a variable outcome.

The coverage can have significant impacts on ultimate performance and in a world of expensive input, low commodity prices and trying to squeak every dollar out of an acre, studies show a lot of room for error.

Consider this soybean trial finding where coverage and canopy penetration were lower than a ground sprayer:

The performance ultimately led to increased white mold severity in the soybean trial and decreased yield:

Some of that is coverage, other aspects might be product formulation related (more on that below).

Atomizers can help

I highlighted work from a Spray Expert Tom Wolf in Is John Deere Losing Ground in Drones or Is the Market Just Not Ready? surrounding atomizer capabilities.

Wolf shares:

Rotary atomizers allow droplet size adjustments through rotation speed, which can offset travel speed and pressure changes without compromising consistency. Many drones today do include a rotary atomizer, like options on the DJI T50.

Low water volumes

Payload capacity is a physical constraint. Most spray drones carry 3-8 gallons, forcing lower application volumes.

• Manned aircraft (200–600 gal tanks) typically run at 2–4 US gal/ac.

• Drones are often pushed lower, to 0.5–1.5 gal/ac.

Low volumes require finer droplets to maintain droplet density, which increases drift and evaporation. The flip side is that lower load capacity mean more refills at higher water volumes. At 2 gal/ac, a drone might only cover a few acres per load (eg: ~8 gal tank), managable for spot spraying, but unproductive for larger fields. This leads to an attempt to increase flight speed for efficiency to cover ground, which can reduce deposition uniformity even more.

For context, you might only end up doing a dozen acres per hour, where as a ground system with 90-120 foot boom and 800-1200 gallon tank is doing 80-100+ acres per hour depending on fill:

Product formulations and surfactants can help, too

Companies like Stepan are creating specific technology for low water volumes/drones, as are essentially every major crop protection company, albeit primarily for Asian based products, but the capabilities (with some adjustments, such as for humidity/temperature variation, would be viable for N. America).

BASF has talked about a new rice insecticide, Prexio® Active, designed for drone compatibility.

Bayer is pursuing similar efforts, investing in suspension concentrate formulations that perform under very-low-volume conditions, with additives and surfactants that help actives spread and penetrate at reduced carrier rates.

FMC has already had conditional approval in the Philippines for drone use of Prevathon® in rice.

Corteva is following a similar path, developing ultra-low-volume formulations optimized for drones and launching a drone-specific product designed for rice.

This can be done through multiple mechanisms.

• Concentrate AI without losing sprayability – smaller particle size (1–3 µm), dispersants plus have co-solvents to keep viscosity low and prevent nozzle plugging.

• Engineer droplet behavior – drift-control polymers and rheology modifiers to tighten droplet spectrum.

• Boost droplet performance on leaves – over optimize surfactants for spreading, stickers for retention, oils/penetrants for uptake.

• Slow evaporation / crystallization – humectants (glycol, glycerol, urea) and anti-crystallization aids to keep droplets liquid and bioavailable, particulalrly in lower humidity environments.

• Stabilize water chemistry – built-in buffers and chelants to manage pH and hardness at low carrier volumes.

• Match mode of action to formulation – contact actives optimized for coverage; systemic actives paired with penetrants, encapsulation, or solvents for uptake/persistence.

• Adapt to UAV hardware – low-foam, sedimentation-resistant systems that run clean in compact pumps and atomizers.

• Prevent fouling at low dilution – low-insoluble, dispersant-rich packages to stop screen plugging and ensure re-dispersion between fast refills.

The above are just some of the mechanisms but it reinforces the need for formulation technology.

Final Thoughts

Rotary drones still struggle with inconsistent swaths, low payloads, and narrow operator margins, making large-scale row crop spraying unreliable beyond spot spraying.

The industry is rworking to navi Rotary atomizers improve droplet uniformity, and majors like BASF, Bayer, FMC, and Corteva are engineering high-concentration, low-volume formulations to fit UAV limits. Meanwhile, fixed-wing drones from companies like Precision AI and Pyka aim to solve the scale problem with larger payloads and broader coverage.