(Updated Aug 19, 2026)

Remote Piloted Aerial Application Systems (RPAAS) or Unmanned Aircraft Spray Systems (UASS) are generally referred to as drones. They are an increasingly common tool for pesticide delivery in modern agriculture. They offer flexibility and access to difficult terrain, are capable of broadacre and patch applications, and facilitate air-assisted applications over perennial canopies. As with all application technologies, careful attention to fundamentals, safety, stewardship, and regulatory compliance remain the cornerstones of responsible use.

This document summarizes the state of the Canadian legal environment at the time of writing, and current best management practices for pesticide handling and application using drones. It is intended to support training and adoption for operators from a wide range of backgrounds. Given the rapid evolution of drone design and the changing regulatory landscape, key considerations are addressed without being overly prescriptive.

Categorization and the Canadian Legal Environment

Drones can be divided into three design categories (Figure 1):

• Rotary-Wing: Single or multi-rotor, these drones employ vertical take-off and landing (VTOL) and can hover during spraying. They have relatively short flight times and low volumetric capacity.
• Fixed-Wing: Resembling crewed airplanes, these drones require a runway for take-off and landing. They have relatively long flight times, operate at higher speeds and have more volumetric capacity.
• Hybrid: Encompassing a range of designs including, for example, parasail-wing and VTOL-wing, this design combines aspects of rotary drones with the speeds, flight times and volumes of fixed-wing designs.

Drones are also categorized by weight, which is used to define their legal use:

• Small Drones (250 g to 25 kg): Typically have tank sizes up to 12 liters and speeds less than 25 km/h (10 m/s).
• Medium Drones (25 kg to 150 kg): Typically have tank sizes ranging from 12 to 70 liters and a maximum speed of 25 km/h (10 m/s).
• Large Drones (>150 kg): Typically have tanks >70 liters and a maximum speed of 72 km/h (20 m/s).

Pesticide use is regulated by both federal and provincial governments to protect human health and the environment. Anyone applying pesticides must ensure they are registered for use in Canada and must comply with all applicable federal and provincial/territorial requirements. Provincial rules vary, and it is the responsibility of the drone operator to understand and follow the requirements in their jurisdiction. 

Transport Canada: Certification

Drone pilots must follow Canadian Aviation Regulations (CARS) Part IX. Drones must be registered and marked, and the pilot must carry valid pilot’s certification.

Table 1 lists each pilot certification (that is, Basic, Advanced, and Level 1 Complex) and permitted category of operation for small, medium and large drones. It is based on Transport Canada’s “Drone Operation Categories and Pilot Certificates: Overview (2025-11-04)”.

Table 1 – Drone Operational Categories and Pilot Certificates

Health Canada: Pesticide Labels

Health Canada is responsible for approving the registration of pesticides across Canada. Pesticide labels are legal documents and set rules on how a pesticide can be used. They define application rates, equipment settings, mixing instructions, environmental precautions, personal protective equipment (PPE), restricted-entry intervals, and disposal instructions.

On June 30, 2026, Health Canada released Science Policy Document SPN2026-02, Allowing pesticide application by drones for products currently registered for aerial application. Users are required to follow all label directions for aerial application, with no changes to spray volume, application rate, droplet size, spray buffer zones, or any other conditions of use specified on the label, with some clarifications regarding nozzle placement, and PPE and safety measures for drone pilots.

Before using drones to apply pesticides, pilots and crew members must ensure they understand provincial requirements, complete any training and certification required and obtain any applicable licenses, permissions and permits for pesticide use that are required by provincial or territorial regulators.

Questions regarding product label interpretations and uses can be directed to the Pesticides Information Service at pesticides-info@hc-sc.gc.ca.

Drone Mission Planning

Proper field mapping and mission planning leads to safe and successful flights. Map obstacles, no spray zones, buffer zones, sensitive area/crops, areas of human activity, terrain, etc. Be aware that these conditions may change if planning occurs too far in advance of the spray day. Always check for relevant Notice to Air Missions (NOTAM), ensure the airspace is not restricted, and be aware of any other aircraft operating in the area.

Staging Area

Ideally, the staging area should be identified and prepared prior to the spray day. Select and clear a location for filling, take-off and landing that is safe for the operator, crew and equipment.

• The staging area should present clear lines of sight and support efficient operations.
• Drones should never fly over, or too close to busy roads.
• The staging area should be upwind of the target site to reduce operator exposure to drift.
• Bystanders must be at a safe minimum distance, as defined by the nature of the operation.
• The operator and crew must be a safe distance from the drone during take-off and landing. Flying over crew is prohibited.
• When spraying large fields, moving to an alternate staging area can save unnecessary ferry time, increasing efficiency and reducing battery strain.
• Identify and be prepared to use connecting points and perform a manual landing when needed.

Tendering System

A drone tendering system is a required component. At minimum, they achieve four things:

• They supply onsite power.
• They store water and chemicals.
• They have a mixing and dispensing capability.
• They transport the drone(s).

Drone tendering systems vary in size, complexity, cost and capacity, depending on the nature of the operation. For example, licensed exterminators (that is, those paid to spray properties other than their own) may have additional needs beyond what is listed here.

Mixing

Drone tanks are small and lack agitation. Therefore, most tendering systems include a nurse tank for pre-blending and agitating batches of spray mix. This helps ensure that active ingredients dissolve and disperse fully, that suspension products stay mixed and that the target site receives a consistent mix.

Water quality determines pesticide effectiveness; hardness, bicarbonate, pH, and turbidity can antagonize or degrade products. Water quality testing allows operators to correct potential problems before spraying. Higher spray volumes (that is, liters per hectare or gallons per acre) enable proper mixing and have been shown to improve spray coverage.

The act of mixing (and filling) carries the highest risk of operator exposure and environmental contamination. PPE requirements must be observed, and operators should avoid distractions or hurried work. Mix only the amount required for the task; leftover pesticide mixes create disposal problems and safety risks.

1. Fill the nurse tank halfway with clean water. Backflow prevention (for example, a valve or air gap) protects the water source.
2. Measure and add the pesticide, following the mixing order on the label and allowing time for each tank mix partner to dissolve and disperse. Tank mixing must be permitted on the label of each tank mix partner. Mixing multiple products at high concentration greatly increases the possibility of physical and/or chemical antagonism. If compatibility is in question, contact the manufacturers for guidance and conduct a jar test well in advance of spraying.
3. Rinse jugs and measuring tools into the nurse tank.
4. Top up with water and maintain agitation throughout the operation.
5. Transfer the spray mix into the drone tank using the most closed system available.

Filling and Battery Management

Rotary-wing drones carry relatively small spray volumes, so refills and battery swaps occur frequently. Large models, for example, might have a 10-minute flight cycle, where the refilling and battery swap processes are simultaneous and comprise less than 2 minutes.

Filling

Haste and inattention increase the chance of spills, overflows and leaks during refilling. This represents unnecessary point source contamination and operator exposure and must be avoided. While drone refills currently involve quarter-turn-valved faucets, or gas-station-style automatic fuel nozzles, neither are ideal. It is inadvisable to remove or otherwise modify the tank lid to expedite filling. Ensure filling is performed with the most closed system available.

Batteries

Batteries, like the drone, carry spray residue and must be handled using PPE. Some battery chargers feature water baths, misters or air conditioning. If water-cooled, treat the water as pesticide‑contaminated and dispose of accordingly. Batteries charge more efficiently and last longer if charged in a cool, ventilated location. Charge according to the manufacturer’s instructions.

Note: At the time of writing, there are new developments in drone tendering that permit autonomous charging and loading. This will reduce the potential for operator exposure and environmental contamination.

Operator Comfort

Drone operations are physically and mentally taxing. Attention to operator comfort improves safety and efficiency. Even seemingly minor accommodations have positive impacts:

• Folding chairs combat operator fatigue.
• RV awnings, umbrellas, foldable Bimini-style tops or flip-up doors provide shade.
• Wear ear protection and consider lower-decibel equipment (for example, inverter gas generators are comparatively quiet, and electric pumps are even quieter).
• Enclose or locate loud components far from the filling area to reduce noise and emission exposure.

Elevated Platforms and Flight Decks

Line-of-sight and Connectivity

While “beyond visual line-of-sight” operations are allowed under specific, authorized conditions, most current regulations require operators to maintain a visual line-of-sight with the drone. This supports swath alignment, obstacle avoidance, an ongoing assessment of drift risk, and general operational safety.

Operating from an elevated platform can help maintain visual line-of-sight and improve connectivity between the flight controller and the drone. Real-Time Kinematic (RTK) is a satellite positioning technique that enhances GPS/GNSS data to provide centimeter-level accuracy in real time. An RTK platform will improve connection reliability and drone accuracy. Satellite internet providers can supplement connectivity in regions with unreliable cellular coverage. Be aware that network latency varies with provider.

The safest approach is for the pilot to control the drone from an elevated platform while a loader performs refill and battery-swap procedures on the ground. However, if operating off a flight deck:

• Long flight decks keep landings and lift-offs at a safer distance.
• Decks with pull-out platforms or hydraulic wings can increase the operating area and can be adjusted to account for adjacent roads and the slope of the ground.
• A security rail around the landing area can prevent a drone from slipping off; A falling drone is expensive, but falling or sliding into an operator is a disaster.
• An enclosed operations area can improve operator safety and comfort.

Remember, the operator should be focused on the drone/controller when flying; Flight is not an opportunity for performing other tasks.

Cleaning

Proper cleaning prevents cross‑contamination, maintains equipment lifespan, and avoids crop injury from residues. Perform cleaning away from open water and ensure rinsate is disposed of responsibly. Follow the pesticide label and adhere to the manufacturer’s instructions on allowable cleaning methods. The following recommendations do not supersede either resource.

Triple‑Rinse Procedure

Multiple, small-volume rinses are more effective than a single, large-volume one. Follow the triple-rinse procedure:

1. Ensure the drone tank is as empty as possible.
2. Fill the drone tank 1/4 full of clean water and, with a partner, agitate by rocking the tank (if removable).
3. Flush the rinse water through the plumbing and nozzles.
4. Repeat the process twice more.

Employ a similar procedure to remove residues from the nurse tank plumbing systems. Important reminders when cleaning:

• Use a cleaning agent in the second rinse if recommended by the label. Soaking may be required.
• While the drone exterior should be rinsed, avoid pressure washing (to protect electronics) unless explicitly permitted by the manufacturer.
• Cameras and Lidar will not function if they are covered in residue. 
• Commercial drone residue removers are available to assist in keeping the drone clean.
• Wash or dispose of PPE according to label and local regulations.

Operational Use Case

Swath Width

For now, consider swath width to be the width of the area sprayed in a single pass. Swath width is a fundamental variable for mission planning, ensuring the pesticide is applied at the correct rate and (in the case of broadacre operations) as uniformly as possible. A rotary-wing drone’s swath width is highly variable and affected by several factors, collectively referred to as the “Operational Use Case”. These factors include:

• Downwash
• Operational settings (for example, altitude and travel speed)
• Meteorological conditions (for example, wind speed, wind direction, relative humidity)

Downwash

When a rotary-wing drone hovers, each rotor draws air from above and accelerates it downward in a high-velocity blast. The result is a vertical component referred to as the “downwash” and the turbulent splash of air that hits the ground and spreads laterally is the “outwash”. Droplets released beneath a drone at hover are almost completely entrained by the downwash. The majority get driven to the ground and then move laterally along the outwash, while a small portion (generally smaller droplets) recirculate back up through the rotors (see Figure 2a).

Most rotary-wing drones have fixed-pitch rotors, so the entire drone must tilt forward to enter low-speed flight. This causes the column of downwash to tilt backward. While the downwash is created by lift, “wake turbulence” is created at the tips of the rotors as high-pressure air beneath the rotor wraps around to the low-pressure area above.

As the drone flies at low speed (~3 m/s) the wake can be visualized as a pair of counter-rotating, cylindrical vortices that trail behind. Spray is still mostly entrained by the downwash on a downward and rearward vector with deposition aligning closely to the flight path. However, a portion will get caught in the wake (see Figure 2b).

The effects of higher flight speeds have not yet been fully characterized. While the additional thrust required at higher speeds may increase downwash energy, the downwash is also carried farther behind the drone and distributed over a larger area. As a result, it becomes less effective at entraining spray droplets and directing them to (or into) the target. Droplets remain suspended for longer, making them more susceptible to wind displacement and increasing the proportion of spray carried within the rotor wake. Overall, these effects tend to widen the deposition pattern and increase swath width.

Evidence suggests that beyond a certain flight speed, swath width reaches a plateau. However, deposition within the swath continues to decrease while displacement/drift continues to increase. Therefore, higher flight speeds can reduce deposition on the target and increase drift potential, making them generally undesirable.

Operational Settings

When configuring a rotary-wing drone for a mission, pilots select operational settings through the controller. Of these, droplet size, flight speed, and altitude (specifically, the distance between the nozzles and the target) have the greatest influence on droplet behaviour and, consequently, swath width. Although the interactions among these factors are complex, some general trends have emerged. These trends can be used to predict how changes in a setting are likely to affect both swath width and drift potential (Table 2).

Table 2 – Effect of rotary-wing drone operational settings on swath width and drift potential.

Meteorological Conditions

Spray released from a drone is highly susceptible to environmental conditions. Drift potential increases when:

• conditions are calm (inversion risk)
• windspeed is too high (physical drift)
• conditions are changeable (gusting and fluctuating wind direction)
• conditions are hot and relative humidity is low (droplet evaporation)

Operators must observe label recommendations, local laws, and use good judgment to minimize drift potential. At minimum, operators should adjusting settings for passes along the downwind field margin to account for swath offset. Practical methods include:

• reducing flight speed
• increasing droplet size
• increasing volume
• reducing altitude (and compressing route spacing)
• halting operations when conditions favour movement toward sensitive habitat / crop / residential areas.

Be aware that certain drift-reducing adjuvants have an unpredictable impact on the droplet size produced by current rotary atomizer designs. Until rotary atomizer design is standardized and tank mixes can be evaluated, do not assume adjuvants will work as intended.

Droplet Deposition

Consider the following operational use case: A rotary-wing drone spraying back and forth over rolling topography will experience changing wind speed and relative direction. The drone will respond by changing drone pitch, rotor speed and pump flow to maintain the desired altitude, travel speed, and application rate. Meanwhile, the drone gets lighter as it sprays, reducing the magnitude of the downwash. Ultimately, this results in a swath width that expands and contracts and may shift back-and-forth or be consistently offset along the flight path (Figure 3).

Deposition studies using vertical targets have shown that when a drone sprays into a headwind, deposits spread laterally to either side of the flight path due to rotor outwash. Deposit density decreases with increasing distance from the flight path. Spray is also carried downward and rearward by the downwash, resulting in greater deposition on vertical surfaces that face the drone as it moves away (revisit Figure 2).

In contrast, a tailwind, even as light as 7 km/h, can carry suspended droplets forward and the deposit cumulatively on vertical surfaces facing the drone’s direction of travel. Similarly, a crosswind shifts the spray plume laterally in the downwind direction.

In summary, when the wind is strong enough to overcome the drone’s downwash, most spray deposits occur downwind of the flight path, regardless of the drone’s direction of travel. This is especially true for smaller droplets.

Evaluating Swath Width

A drone’s swath width for a given operational use case must be determined through testing. The drone is first calibrated according to the manufacturer’s instructions. Swathing methods vary, but generally the drone is flown into the prevailing wind over a series of samplers (for example, discreet samplers like water sensitive paper or continuous samplers like string or bond paper). This creates a cross-section of the spray deposition (Figure 4).

Multiple passes are required to capture the variability that occurs along the flight path. Swath width is calculated for each pass and then averaged, as opposed to averaging deposition data and calculating a swath width. The later practice conceals variability, resulting in a larger swath width and a more uniform distribution than can be consistently achieved in practice.

Acceleration and Deceleration

Swath width produced by a rotary-wing drone varies with flight speed, up to an estimated (but not yet confirmed) limit of approximately 10 m/s. As a result, swath width increases as the drone accelerates at the start of a pass and decreases as it decelerates toward the end.

Unlike crewed aircraft—which reach and maintain target speed before spraying—current software limitations prevent drones from separating flight and treatment zones. Further, some drones will climb into the turn, ostensibly to reduce the impact of downwash on delicate canopies, but this did not appear to diminish the affect on swath width.

To maintain uniform coverage, additional headland passes may be required at the beginning and end of each flight pass (see Figure 5).

Route Spacing and Overlap

A rotary-wing drone does not deposit spray uniformly across its swath. Deposition is typically greatest beneath the drone and decreases with distance from the flight path, creating a bell-shaped distribution (revisit Figure 4). In the presence of a crosswind, this distribution becomes skewed in the downwind direction.

Route spacing, which is entered into the flight controller, determines the distance between adjacent flight passes, but it does not influence the swath width itself. For example, if testing indicates a swath width of 9 m, entering a route spacing of 10 m will not increase it.

When uniform broadacre coverage is the objective, adjacent swaths should be overlapped to create the flattest possible combined distribution. For a series of similar, near-normal deposition curves, this occurs when neighbouring swaths overlap at approximately the full width at half maximum of the distribution. In practical terms, the centres of adjacent passes are spaced so that deposition from each pass has declined to about 50% of its peak value at the point where the two profiles meet.

It may seem that a crosswind would improve uniformity by spreading deposits over a wider area. However, crosswinds produce skewed deposition patterns rather than symmetrical bell curves. Modelling shows that when these asymmetric profiles are overlapped at regular intervals, their steep leading edges and long trailing tails do not balance. Instead, they create areas of excessive and insufficient deposition, resulting in pronounced peaks separated by broad, shallow valleys. As skew increases, uniform coverage becomes progressively more difficult to achieve, and no single route spacing can fully compensate for the asymmetry of the deposition pattern.

Agronomic Use Case

Effective Swath Width

We must now refine the concept of swath width. Some drone manufacturers define swath width as the distance between the furthest detectable spray deposits. However, detecting a deposit during testing does not necessarily mean enough product has been deposited to achieve the desired result. As a result, application efficacy can vary across the swath, even within the measured limits of detectable deposition.

A more practical definition is the Effective Swath Width (ESW), which is the maximum pass spacing that achieves the desired biological result while minimizing over- and under-dosing between adjacent passes. Determining the ESW requires establishing a minimum threshold dose, or put simply, “how much is enough?” Traditional aerial application methods often assess deposit uniformity using the coefficient of variation (CV) and estimate the efficacy threshold as 90% of the maximum deposition. Online tools are available to help calculate ESW from measured deposition patterns.

The need for an ESW becomes apparent at the outer edges of the swath, where deposition is often too sparse to provide reliable control. Therefore, the Effective Swath Width is influenced by the Agronomic Use Case, which includes factors such as:

• Minimum Effective dose: This is a complex relationship between coverage, spray mix concentration and pesticide mode-of-action. It is a threshold or narrow range that elicits an effective result while minimizing waste.
• Target location (for example, a pest within a dense canopy or a weed on relatively bare ground)
• Spray mix rheology (that is, the interaction of spray mix viscosity and atomizer design on droplet size)

Minimum Effective Dose

Consider a systemic herbicide and a contact fungicide. A herbicide mixed according to the label will kill weeds with less volume per hectare and less target coverage than is required for most fungicides and insecticides. Therefore, a herbicide can still be effective at the extremes of the swath, whereas a fungicide may not.

Somewhere towards the middle of a drone’s steep deposition curve, the dose becomes excessive. If uniform broadacre coverage is the objective (as opposed to a directed application into a perennial, three-dimensional canopy), this represents waste. In exceptional circumstances, such as certain horticultural crops or GMOs with stressed metabolisms, it could potentially cause phytotoxic damage.

Therefore, two missions with identical operational use cases, but different agronomic use cases, can present the same swath width during testing, yet have different Effective Swath Widths. This distinction is important when establishing route spacing, which should match the effective swath width (see Figure 6).

Target Location

Spray coverage diminishes with canopy depth. The degree depends on crop morphology and planting architecture, as well as certain operational settings such as volume, droplet size and flight speed. Simply put, a plant canopy filters out spray droplets, and this occurs both vertically and laterally. This is not represented during typical swath measurements, which tend to take place on bare ground.

Spray Mix Rheology

Most conventional hydraulic nozzle designs adhere to an international standard. This allows the operator to determine the size of droplets produced for a given operating pressure and flow rate. Droplet size is a not only a critical factor in mitigating drift and improving spray coverage, but also affects product efficacy (for example, droplets that stay wet longer tend to improve herbicide efficacy).

Currently, most rotary-wing drones use rotary atomizers positioned within the rotor downwash. Rotary atomizer designs are not standardized, and their performance can vary considerably. Some atomizers are prone to “flooding” when the liquid flow rate exceeds their capacity. When this occurs, the atomizer produces a greater proportion of large droplets, which can reduce coverage quality and overall application efficacy.

As a result, the droplet size selected in the controller does not necessarily reflect the droplet size actually being produced. Research has shown that factors such as atomizer design, flow rate, spray mix composition, product concentration, and the use of adjuvants can significantly alter droplet size, producing droplets that are either much larger or much smaller than intended.

This variability creates a practical challenge for operators. When a pesticide label specifies a particular droplet size, it can be difficult to verify that the spray being produced by the drone is actually within the required range. Until rotary atomizers are standardized (or there is a return to conventional nozzles), operators can only select the desired size and infer the results based on in-flight behaviour and observing the size of the stains left on samplers during swath width testing.

Practical Impact

Taken collectively, research has shown a 20 to 30% reduction in ESW for corn, wheat and soybean fungicide applications compared to swaths measured on open ground. It is presumed that any complex canopy will reduce ESW to some degree.

Conversely, research and field observation suggest that herbicides sprayed on bare earth or sparse vegetation can produce an efficacious response wider than the measured swath width (see Figure 7). This is not a constant because it is a function of the dose, the prevailing wind direction and a possible underestimation of calculated swath width from 2D sampling methods.

The impact of agronomic use case on ESW must be considered during mission planning, as this may warrant further adjustments to route spacing.

Record Keeping

Detailed record keeping will help operators better understand how operational and agronomic use cases affect the outcome of a spray mission. Quality records also help mitigate against any allegations of misapplication, such as a drift complaint. The following items should be recorded, but the list is not exhaustive:

• Product name(s), rate(s) and water volume.
• Sprayer operational settings (altitude, speed, route spacing, droplet size to supplement a digital record of the mission)
• Swath measurements
• Weather conditions
• Note of buffers and sensitive areas
• Crew names and roles
• Unusual events or corrections
• Results (return to site to assess efficacy)

Conclusion

Drone technology is advancing rapidly, and best management practices will continue to evolve with new research and more experience. However, the principles in this document—proper preparation, careful mixing, responsible application, diligent maintenance, environmental awareness and swath testing—apply regardless of model or agronomic use case.

Operators must ensure they are properly licensed and comply with all applicable federal and provincial requirements, including those related to the sale, use, transportation, storage and disposal of pesticides. With thoughtful planning, practice and record keeping, drones can be a safe and effective means of crop protection.

Thanks to Dr. Steve Li (Auburn University, College of Agriculture) and Dr. Michael Reinke (Michigan State University Extension) for their review of, and contribution to, this article.

Resources

• Airblast101 – Your Guide to Effective and Efficient Spraying. 2nd Edition. Deveau, J., Ledebuhr, M, Manktelow, D. Jan. 2021. ISBN 9781006916335.
• How to Calibrate a Drone. Wolf, T., Deveau, J. Apr. 2023.
• RPAS Coverage and Drift in Field Corn. Deveau, J., Ledebuhr, M. Jul. 2023.
• Best Management Practices for Safe and Effective Application of Pesticides Using Unmanned Aerial Spray Systems (UASS). Unmanned Aerial Pesticide Application System Task Force, Sep. 2024.
• RPAS swathing in broad acre crop canopies. Deveau, J. Nov. 2024.
• Characterizing RPAS coverage at four cardinal points on a vertical plane: Practical implications for spraying wheat at T3. Deveau, J. Jun. 2025.
• The Carvalho Boom and the Stages of Quadcopter Flight. Deveau, J. Feb. 2026.
• Drone Tendering – Considerations before Buying or Building. Deveau, J. Feb. 2026.
• Drone-Based Herbicide Application: Opportunities and Challenges Olumide S. Daramola, Thomas R. Butts, Simerjeet Virk, Bholuram Gurjar, Ubaldo Torres, Muthukumar Bagavathiannan, J. Anita Dille, Augustine K. Obour, Koffi Badou-Jeremie Kouame. Weed Technology. Feb. 2026.
• The Hidden Shape of a Drone’s Spray Swath: What 2-D Imagery Reveals. Falk, K. Mar. 2026.
• Droplet trajectories from rotary spray drone application: Implications for swath width measurements. Deveau, J., Wolf, T. Mar. 2026.
• A Drone’s Swath Width Tapers with Speed. Deveau, J. May 2026.