Author: Jason Deveau

  • The Carvalho Boom and the Stages of Quadcopter Flight

    The Carvalho Boom and the Stages of Quadcopter Flight

    The Hypothesis

    The results of a recent herbicide deposition study performed with the DJI T100 led us to observe that after ~13 m/s, swath width and drift were no longer directly related to travel speed; They appeared unaffected. The result was completely unexpected as it was counter to several years of prior study with smaller drones. This led to a hypothesis that the aerodynamics of this new generation of quadcopters might be similar to that of a helicopter, and it was impacting spray deposition in a similar fashion.

    Let’s use the stages of quadcopter flight to set up the premise.

    1. Hover

    When a drone hovers, each rotor draws air from above and accelerates it downward in a high-velocity blast. The cumulative effect 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”.

    The initial strength of the downwash depends on the degree of “disc loading” which is the weight of the drone divided by the rotor area. The intensity of the downwash wanes with distance from the rotor, spreading out in three dimensions until it impacts the ground and becomes the outwash.

    During hover, the drone recycles some of its downwash. This turbulence affects the stability of the drone, requiring a great deal of power to stay aloft, especially when it’s full.

    2. Low-speed flight

    A helicopter achieves forward thrust by changing the pitch of its rotor blades. Most 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 is visualized by a pair of counter-rotating, cylindrical vortices that trail behind. Some journal articles suggest the downwash for medium-sized drones (e.g. < 50 L capacity) detach from the ground at speeds as low as 3 m/s.

    3. Effective Translational Lift (EFT)

    As the drone accelerates it continues to angle forward, likely not exceeding 30°. At some point (~15 m/s?), we suggest it enters a state of “effective translational lift”, becoming more stable and therefore more energy efficient. This speed is notably slower than is commonly reported for a helicopter.

    During the transition, the drone behaves more like a wing as it essentially outruns its downwash, moving undisturbed air over the rotors. This horizontal air provides some lift, making flight more energy efficient, at least until drag begins to pull on the drone.

    The Possible Effect of Flight Stage on Spray Behaviour

    Droplets released beneath a drone at hover are completely entrained by the downwash. The majority get driven to the ground and then laterally along the outwash, while some small portion (likely smaller droplets) recirculate back up through the rotors.

    At low-speed flight, the downwash begins to tip backwards and the downwash trails behind and at some point detaches from the ground. Spray released beneath the drone is still entrained and will trail on a downward and rearward vector in that downwash. However, a portion will get caught in the wake. We can sometimes see this spray separation occur when lighting conditions are just right.

    As speed continues to increase, much of the spray would still be entrained in the downwash, but a greater portion would get caught in the wake, appearing as spray curling at the extremes of the swath. At some point, perhaps if and when the drone enters EFT, the the downwash might be less chaotic and behave more like laminar air. In which case some spray would still curl in the wake, but much of it would fall in a more stable sheet. Further increases in speed would not affect spray behaviour appreciably.

    Taking Advantage of ETL

    If this is the case, it is conceivable that rotary atomizers positioned under the front rotors could fling some droplets beyond the leading edge of the downwash. What if instead, it were a horizontal boom positioned out in front of the rotors, transecting the chord line?

    As the drone tipped forward during high-speed flight, so too would the boom, bringing it closer to the ground and releasing droplets ahead of, and below, the leading edge of the downwash. This should produce a more uniform swath, perhaps subsequently pushed down as the drone passed over.

    It’s an interesting idea that is only made possible when drones are capable of high-speed flight.

    Reception

    In January 2026 I presented this concept during a lecture at the 4th annual Drone End-User meeting in Kansas City. The response was polite, but skeptical. I then shopped the idea around the trade show floor where drone manufacturers suggested a front-mounted boom would interfere with obstacle avoidance sensors, or shift the centre of gravity, making the drone difficult to fly and to land. And what about the impact of wind speed and direction? All good points. Then, Nino Carvalho introduced himself.

    The Carvalho Boom

    Nino Carvalho and his son, Emilio, own and operate NC Ag Spraying in the Central Valley of California, USA. Emilio was inspired to modify his drone after discussing matters with his mentors; one who owns and operates a fixed wing aerial business, and another that pilots a Huey helicopter. In late 2025, they designed and built a horizontal boom which I’ve dubbed “The Carvalho Boom”.

    Their first attempt was with a DJI T50, but the boom mount interfered with the stacked rotors, and the atomizer cables were difficult to extend. The XAG P150 had fewer cables and only top-mounted rotors, so it was a better fit. After experimenting with various materials (PVC was too flimsy, steel too heavy) they mounted a length of ½ inch metal conduit directly under the drone.

    In California, aircraft booms must be limited to 90% of the rotor width (because of rotor tip vortices). The greatest span of the rotors was 312 cm (122.8 in), so they made the boom 275 cm (~9 ft) long. They spaced the rotary atomizers evenly along the boom every 69 cm (~ 2 ft 3 in), extended the original 30.5 cm (12 in) nozzle cables to 305 cm (10 ft) to reach their respective electronic speed controllers, and plumbed them using 1.25 cm (0.5 in) diameter tubing.

    They flew this first prototype over water sensitive papers. Dropping from a 3 m (10 ft) altitude to 2 m (6.6 ft) improved coverage uniformity and resulted in a 10.3 m (34 ft) effective swath width. They could see the downwash was interfering with deposition, and while increasing to a larger droplet size helped, it didn’t help enough. Then they made some design changes, extending the boom 30.5 cm (12 in) beyond the rotors, and they saw they had something. They reached out to Agri-Spray Consulting (Nebraska) and arranged to run a series of Operation S.A.F.E. fly-ins.

    There were more than 25 flights that day, so we’ll focus on three specific load-outs. The critical parameters are listed in the following table in the order that they flew them. The first load-out (N7696-01) was deemed the best, and was the only one with the boom extended out front, beyond the rotor tips. This information is italicized. The other two are included here for interest. N7696-03 attempted to shift the boom back under the drone for cosmetic reasons, but also for ease of transportation. N7696-04 was the same configuration as the last, but with coarser droplets in an attempt to battle the downwash. The first fly-in report (N7696-01) is shown below, but all three reports can be downloaded by clicking the links above.

    Load-OutBoom PositionVolume Speed Droplet Size (µm)Altitude Wind VelocityEffective Swath WidthC.V. (Race Track / Back & Forth)
    N7696-01Beyond Rotors50 L/ha
    (5 gpa)    		16 m/s
    (36 mph)    		2302.75 m
    (9 ft)    		10.7 kmh
    (6.7 mph)    		10 m
    (33 ft)    		10%/10%
    N7696-03Beneath Rotors50 L/ha
    (5 gpa)    		16.5 m/s
    (37 mph)    		2302.75 m
    (9 ft)    		12.5 kmh (7.7 mph)7.6 m
    (25 ft)    		9%/11%
    N7696-04Beneath Rotors50 L/ha
    (5 gpa)    		14.3 m/s
    (32 mph)    		4002.75 m
    (9 ft)    		8.5 kmh
    (5.3 mph)    		8.5 m
    (28 ft)    		18%/11%

    Observers said it looked like the swath was rolled with a paintbrush and that there were no observable vortices – just a sheet of spray. The following videos show some of the passes from that day. Actually, you can see vortices, but only in the passes where the boom is positioned beneath the rotors and not when it’s extended out front.

    A 10% CV is spectacular, and the profile of each pass (even before averaging) was far flatter than any drone deposition I’ve seen previously. This design has not yet been used for custom application because there are still questions about how flight speed and pump flow will affect performance. But, the Carvalhos are already discussing the next design, constructed with carbon fibre tubes.

    Impacts and Musings

    Perhaps our description of how the air is moving over the drone is correct, or perhaps it isn’t quite right. Dr. Fernando Kassis Carvalho (no relation to Nino and Emilio) (AgroEfetiva, Sao Paulo, Brazil) recently shared that he also observed swath width no longer changed at speeds exceeding 13 or 14 m/s (personal communication). So, whatever the aerodynamic cause, the result seems clear.

    Does this mean we’ll see a new generation of quadcopters with front mounted booms? It’s certainly possible, and kind of poetic as some early drone designs featured a centrally-mounted boom that extended beyond the rotor tips. Emilio wondered aloud about possible wear on the front motors, and likely there will be other issues as they experiment, but it’s early days and they’re enthusiastic about pursuing the design.

    Nozzle Design

    Should we also consider a return to hydraulic nozzles? The rotary atomizers on a drone currently leave a lot to be desired. Dr. Ulisses Antuniassi (Prof., Sao Paulo State University) studied the spray quality produced by rotary atomizers. He ran atomizers from a DJI T40 and from a XAG P60 in a wind tunnel spraying WG and SL formulations with either MSO or NIS adjuvants and found no logical trends in VMD, relative span or DV 0.1

    Further, work by Dr. Steven Fredericks (Land O’Lakes) showed that the rotary atomizer from a DJI T40 created droplets roughly one ASABE category smaller than the software indicated. Conversely, common knowledge is that the XAG P100 version produces a coarser spray quality than anticipated, and slow motion video produced by Mark Ledebuhr (Application Insight LLC) and Dr. Michael Reinke (Michigan State University) clearly showed the flooding issue reported by Dr. Andrew Hewitt (University of Queensland), where excessive flow to the disc interferes with its ability produce a uniform droplet size.

    I photographed no less than nine different rotary atomizer designs while at the End-User meeting. So, perhaps we should embrace a standardized design, or perhaps hydraulic nozzles should make a comeback. If the later, it would be a great opportunity to include PWM to increase their flow range.

    Acceleration and Flight Pattern

    And what of kinematics? A drone’s “acceleration time” is calculated by dividing the change in velocity by the acceleration rate. We’ve seen that a DJI T100 must travel up to 100 m before it reaches target velocity. Admittedly, it was full and attempting to fly at high speed. Kevin Falk (Corteva Agriscience) noted a 25 m acceleration distance and a 15 m deceleration distance for a T50 flying mostly-full at 6 m/s. That’s a not-insignificant distance to achieve target flight speed.

    What happens to the spray from a quadcopter drone with a front mounted boom as it transitions through the stages of flight? We don’t know for sure, but we can infer an inconsistent swath. Perhaps the prolonged acceleration time is sufficient reason for drones to start flying racetrack flight patterns like planes and helicopters, where they reach sufficient speed before passing over and spraying the target area. Current software does not allow that practice.

    All this to say that as drone design continues to evolve, we must continue to challenge and test assumptions surrounding best practices. It has been fascinating to see how spray drones are finding their place in Western crop protection systems.

    Acknowledgements

    Thanks to Mark Ledebuhr (Application Insight LLC), Dr. Michael Reinke (Michigan State University), Kevin Falk (Corteva Agriscience), Dr. Tom Wolf (Application Research & Training), Adrian Rivard (Drone Spray Canada), and Adam Pfeffer (Bayer Crop Science) for insightful discussions.

    Special thanks to Nino and Emilio Carvalho (NC Ag Spraying) for sharing their experience and practical approach to improving drone spray deposition.

    Additional Resource

    In early February, 2026, I gave a short interview with RealAgriculture. We discussed the state of spray application by drone in Canada as well as some of the possible impacts of higher speeds.

  • Wanted: A New Technology for Assessing Spray Coverage – The Spray Doctor

    Wanted: A New Technology for Assessing Spray Coverage – The Spray Doctor

    “If you can’t measure it, you can’t improve it”. While the source is nebulous (Peter Drucker, Lord Kelvin, or Antoine-Augustin Cournot), the sentiment is clear.

    The status quo

    In the world of crop protection, considerable resources are expended to distribute a pesticide over a target. And yet, sprayer operational settings and spray coverage are rarely assessed. As a result, too much time elapses between the application and observing the biological results to evaluate and correct equipment performance. The damage (be it waste or an inconsistent and sub-lethal dose) is done. All sprayer operators know this to be true, so why do precious few perform these assessments?

    Perhaps, dear reader, you have personal experience assessing coverage and already know the answer. Perhaps you’ve performed the iterative dance that is placing, spraying, retrieving, assessing and re-placing water sensitive paper (WSP). Perhaps you’ve sprayed fluorescent tracers and hunted for faint glows at twilight using UV lights. Perhaps you’ve looked for residue from diatomaceous earth or fungicides. Or, perhaps, you’ve trusted in the falsely-comforting “shoulder check” and assumed dripping must mean you’ve hit the target.

    Existing methods are complicated, subjective, messy and time-consuming. We need an alternative.

    The alternative

    Consider a permanent, solar-powered sensor that supplies real-time spray coverage data to your smartphone via a cellular connection. The output could be visualised in a simple and intuitive way, and immediately available to both sprayer operators and farm managers. If the sensor was relatively inexpensive, sufficiently hardy, and easy to deploy, its utility would only be limited by your imagination:

    • Stakeholders could confirm the correct functioning of their equipment before committing to the application. Decisions could be made to change operational settings, repair equipment, or delay until conditions improved.
    • The sensors would provide coverage data specific to their location and orientation. Units could be installed in difficult-to-spray regions such as treetops, or canopy-centres, or fruiting zones. Sensors could be placed where pest/disease pressure has been historically high, or where wind is a known issue.
    • Large operations could install them in a test-row, where sprayer operators would perform a gauntlet-style calibration run prior to a day of spraying.
    • Spray records could inform compliance audits, supplement insurance or CanadaGAP traceability requirements, or be used in agronomic assessments.

    In 2025 I was approached by an Australian developer who claimed he had a device that did all of this. And, if that weren’t enough, it could also monitor certain meteorological factors such as pre-spray moisture levels and temperature and report post-spray evaporation rates. I could barely contain my excitement. A prototype was in my hands a few weeks later.

    Prototype, 8-sided sensor located in a blueberry bush.
    Solar panel powering three, 8-sided prototype sensors spanning 10 meters of highbush blueberry.

    Benchmarking the sensor

    The Spray Doctor (working name for the prototype) started its life as a leaf wetness sensor, evolving into a spray coverage sensor piloted in 2023/24 in Australian and New Zealand grape production. The history of earlier iterations and company schisms is convoluted, and fortunately immaterial to our purposes. All I needed to know was that we weren’t starting from scratch. Several of the questions regarding how accurately the surface could detect spray deposition were already addressed by independent research.

    The sensing surface is impregnated with an array of capacitive wetness sensors. The sensor responds to the surface area covered and not deposit density. Researchers reported a reliable response range between ~10% and 50% surface coverage. Given the arguable “ideal” coverage standard of 10-15% surface area, this includes the range of interest for most sprays.

    Benchmarking against WSP was part of the foundational assessment. A droplet of water deposited on WSP produces a high angle of contact and very little spread, while the same droplet deposited on plant tissue tends to produce a lower angle of contact and more spread. This means the stain produced on WSP is smaller than would be produced on plant tissue, depending on how smooth, vertical or waxy the tissue surface was.

    It was therefore surprising that WSP were found to report a higher degree of spray coverage during water-only sprays than the sensor. It seemed droplets more easily coalesced and ran off the sensor surface. This was ultimately interpreted as an advantage, because the sensor would better emulate how a leaf surface would respond to the influence of surfactants and spray quality.

    Adding a surfactant to a spray solution improves droplet adherence, and/or reduces surface tension, improving the degree of contact on plant surfaces. Likewise, it was found that surfactants increased the degree of coverage reported by the sensor, and when actual chemistry was sprayed (e.g. sulphur powder or copper sulfate) there was an effect on the degree of coverage reported. This is unlike WSP, where adjuvants and chemistry do little to increase the spread.

    And so, like every method for assessing spray coverage, the sensor has limitations and caveats. If you have some doubt as to the sensor’s accuracy, do not get distracted by the fine detail. Remember, most operators currently have no feedback whatsoever; even a binary response (e.g. hit or miss) would be welcome. The sensor is sufficiently sensitive and consistent to resolve coverage in a range relevant to most sprays, and therefore worth field testing.

    The experiment

    My role in this story was to work with a grower to evaluate the sensor’s ability to report coverage information in a clear and actionable way. There were three questions:

    • Does data from the sensor influence a sprayer operator’s behaviour?
    • Does that change in behaviour lead to improved spray coverage (implying more efficient and effective crop protection).
    • Could we “dial in” the hardware and the interface based on the grower’s feedback?

    In part two, we share our experience installing and using the Spray Doctor, as well as supply answers to these questions. Stay tuned.

    Thanks to Brandon Falcon (Falcon Blueberries) for volunteering his time and farm for this evaluation, and the developer for the in kind donation of the prototype Spray Doctor.

  • Crop-Adapted Spraying in Highbush Blueberry: Nine years of pesticide savings

    Crop-Adapted Spraying in Highbush Blueberry: Nine years of pesticide savings

    This case study is taking place on a 15 acre highbush blueberry operation in southern Ontario. In 2016, considerable pressure from spotted-wing drosophila (SWD) prompted the growers to make changes to their crop management practices and their spray program. They employed a three-pronged approach to improving crop protection:

    1. Significant changes to canopy management and picking / culling practices
    2. Investing in a new sprayer
    3. Adopting the Crop-Adapted Spraying (CAS) method of dose expression

    We have been tracking pesticide use, water use and yield compared to historic values. We also monitored spotted-wing drosophila catches both in crop and in wild hosts along the border of the operation for three years.

    Canopy Management

    In 2016 the operation made the following changes to their canopy management practices:

    • They performed their first-ever heavy pruning and planned to to maintain an ideal crop density by removing ~30% plant material annually. This more-or-less took place.
    • They regularly collected and buried culled and dropped berries.
    • They picked cleanly and more frequently.
    Heavy pruning in 2016.
    Most years, bushes were pruned ~30% to maintain an ideal size and shape.
    Pickers were educated in how to pick cleanly and dropped / culled fruit was collected and buried.

    There were initial concerns that such dramatic pruning would reduce production per acre and require trellising to prevent berries weighing down the smaller bushes. However, in 2017 (and thereafter) they found that the quality of the berries was greatly improved and noted fewer hours spent culling berries during packing. Financially, the growers felt they came out ahead.

    Application Technology

    In 2018 they replaced their old, inefficient KWH sprayer with a low profile axial with conventional hydraulic nozzles to permit greater control of the spray. The KWH design was intended for standard fruit trees. It produced >100 mph air and an Extremely Fine spray quality and was therefore a bad fit with the planting architecture and canopy morphology of highbush blueberry.

    They considered a cannon-style sprayer hoping to spray multiple rows in a single pass but given the desire for improved coverage and reduced waste, they elected to drive every row using a low-profile axial.

    Fore: An old KWH air shear sprayer. Rear: Low profile axial sprayer with conventional hydraulic nozzles.

    The new sprayer was more reliable, quieter, and more fuel efficient. Further, the old sprayer leaked and the air-shear nozzles did not respond when shut down at the end of rows. Eliminating these sources of waste represented a savings of ~20% of the spray volume traditionally used per acre.

    Crop-Adapted Spraying

    The redundancy inherent to product label rates for three-dimensional perennial crops has long been recognized. In response, rate adjustment (or dose expression) methods have been developed to improve the fit between rate and canopy coverage (e.g. Tree-Row Volume, PACE+, DOSAVIÑA). Each has value, but their adoption has been slow because they are region- or crop-specific and they can sometimes be quite complicated.

    CAS lends structure and repeatably to the informal rate adjustment methods already used to spray three-dimensional perennial crops (e.g. Making pro rata changes by engaging/disengaging nozzles in response to canopy height or altering travel speed in response to canopy density).

    The CAS method relies on the use of water sensitive paper to confirm a minimal coverage threshold of 85 deposits per cm2 as well as 10-15% area covered throughout a minimum of 80% of the canopy. Using this protocol, we calibrated air energy and direction, travel speed and liquid flow distribution. This process is covered in detail here and in the new edition of Airblast101. In that first year we reassessed coverage every few weeks between April and June using water-sensitive paper.

    Spray volume / Pesticide

    By matching the sprayer calibration to a well-managed canopy, the growers were able to go from ~1,000 L/ha to ~400 L/ha of spray mix. The ratio of formulated product-to-carrier remained the same, but less spray was warranted per acre. Stated differently, the grower mixed the spray tanks per usual, but drove further on a tank.

    This also saved an estimated 15 hours of filling/spraying time per year, which translates to reduced operator fatigue and exposure as well as reduced manhours and equipment hours.

    The decision of what and when to apply was at the growers’ discretion. Chemistry was rotated and applications were made according to IPM in early morning (if there were no active pollinators) to avoid potential drift due to thermal inversions. The following image shows what those papers looked like in June of the first year.

    Example of water sensitive paper coverage on a windy day (worst case scenario) in June, 2018.

    Note how little spray escapes the target rows in the following video. The wind was too high for spraying, but we were only using water and saw it as an opportunity to test a worst-case scenario. Air-induction hollow cones were used in the top nozzle position on each side so droplets were large enough to fall back to ground if they missed the top of the canopies.

    SWD monitoring

    SWD represents a serious economic threat to blueberry operations. Traps were placed in the operation (three in the crop and one in an unmanaged wild host along a treeline) and monitored weekly. Traps were also placed in surrounding horticultural operations which were employing standard pest control practices. This not only provided regional information about SWD activity but allowed us to compare the level of SWD control from the Crop-Adapted Spraying approach.

    • In 2018 the comparison included up to 16 other sites that were berry and tender fruit.
    • In 2019 the comparison included 10-12 sites (depending on the week) and they were berry and tender fruit sites.
    • In 2020 the comparison included 4 other sites (blueberries, raspberries and cherries).

    2020 & 2021 – Covid 19 and Heavy Rain

    In agriculture, every year is an adventure, but 2020 and 2021 were exceptionally difficult and the circumstances should be considered when deciphering the results. Covid-19 has had a significant impact on global agriculture.

    In 2020, fearing a reduction in the availability of seasonal labour, the operation pruned their bushes heavily. This was done to reduce the yield in order to make harvest manageable.

    In 2021, labour was once again secure. Given the heavy pruning the year previously there was no need to prune again, so the crops densified. This coincided with abnormally high levels of precipitation to create significant anthracnose issues. Additional fungicide applications took place that raised costs, but the grower maintained CAS-optimized rates and sprayer settings.

    Quantitative Results

    Prior to replacing their sprayer, and adopting CAS, the operation sprayed about 78,260 L/yr. Their average savings in spray volume (water) has been 54,720 L/yr, or 70%.

    In terms of pesticide savings, we compare each year to the 2017 baseline. In order to make for a fair comparison, we update pesticide prices each year using current costs. Therefore, the 2017 total has increased by about $2,600.00 (wow). Their average savings represents $5,575.00 CAD/yr or 62.5%.

    Yield is more difficult to interpret due to mitigating circumstances in 2019 and 2020:

    • In 2016, prior to any changes, they harvested 12,076 flats (about 9lb of fruit each).
    • In 2017, following the canopy management changes, harvest increased to 18,335 flats (~50% increase).
    • In 2018, using CAS, harvest was essentially unchanged compared to 2017, which was excellent.
    • In 2019, harvest started a month late compared to previous years. Further, blueberry prices were low, and the operation elected to stop harvesting a month early. However, when those issues are factored in, the harvest was comparable.
    • 2020 was particularly challenging for agriculture and with the possibility of reduced labour due to the pandemic, the operation elected to prune heavily and reduce their yield.
    • 2021 saw unpruned bushes (following the heavy pruning in 2020) and abnormally high levels or precipitation which created anthracnose issues. As a result, more applications were made than any other year on record, but maintained the CAS-optimized rates and sprayer settings.
    • 2022 was (thankfully) fairly typical. Low SWD, average anthracnose and no drama.
    • 2023 was very much like 2022 with low SWD, average anthracnose and no drama.
    • 2024 saw a LOT of rain. The season started and ended early, but yields were par. “Pivot” replaced “Tilt”.
    • 2025 was pretty average all things considered. No drama whatsoever. “Inspire-Super” was added to product list.

    Trap counts for SWD were only performed during three years of the CAS study, so we are only able to present 2018-2020 data. It should also be noted that while the presence of SWD in an operation represents an impact on yield, there is not necessarily a correlation between the number of SWD captured the amount of damage.

    In 2018 and 2020, average counts were higher in the surrounding operations employing standard practices (STD) compared to the CAS trial. In 2019, average counts were higher in the CAS trial. When total average counts are compared, the difference is negligible. Berries were tested regularly by the growers and the damage due to SWD was within acceptable limits. It should also be noted growers monitored and reported satisfactory disease control throughout the study.

    We have not applied any statistical rigor, but the trend suggests that the level of control provided by the CAS method was comparable to conventional methods. This conforms with our previous results in Ontario apple orchards and similar evaluations of optimized application methods world wide.

    Qualitative results

    Beyond the quantifiable results, the growers reported qualitative benefits:

    • Customers of the U-pick portion of the operation regularly enquire about pesticides. The operation’s reduction in pesticide use became a positive speaking point and aligned with the grower’s philosophy about reduced environmental pesticide loads.
    • While many blueberry growers experienced a market shortage of certain fungicides in 2018, this operation returned unused product to the distributor.
    • Growers reported less early-season disease damage, which saved considerable time on the packing line because there was less fruit to cull. Disease levels rose to typical levels later in the season, but there was still a net savings in labour.

    Conclusion

    The success enjoyed in this berry operation was a result of several canopy management and crop protection changes. This is a situation where the whole equaled more than the sum of its parts – it could only be achieved by making holistic changes to the operation. At the end of three years the growers themselves stated:

    “Based on my experience losing multiple crops to SWD, I can say with absolute certainty it works. <The results are> superior to what I expected. What we are doing is successful.”

    Here’s a narrated PowerPoint presentation of this study (includes data up to 2020):

    The monitoring portion of this project was funded by Niagara Peninsula Fruit and Vegetable Growers Association, Ontario Grape and Wine Research and Ontario Tender Fruit Growers in collaboration with private consultants.

  • The Micothon M2 – The Benefit of Air-assist Spraying in a Vegetable Greenhouse

    The Micothon M2 – The Benefit of Air-assist Spraying in a Vegetable Greenhouse

    I’ve experienced a few spectacular failures trying to build niche sprayers. Until now, I haven’t had a reason to write much about them. But I decided the contrast, and confession, would be a fun way to set the scene for a discussion about an excellent niche sprayer.

    Failed Attempts

    First, the ill-fated “Hops Sprayer”. We used an adjustable ladder to position 20 feet of arborist guns between hop rows. The nozzles could be raised and engaged to match the growing crop canopy. While it left decent coverage on the adaxial surfaces, we quickly realized it needed air-assist to get under the leaves and battle high winds at the top of the trellis. It’s since been cannibalized for parts, and the rusted remains haunt me whenever I drive by the outdoor storage area at our ag research station.

    The Hops Sprayer. A 3 point hitch, vertical boom that could adapt to match canopy height.

    Later, encouraged by a minor success ducting a backpack mist blower with PVC and Coroplast, I tried building an air-assisted spray cart for a floriculture operation. It featured commercial, high-volume radial fans paired with hollow cone nozzles positioned in front of the air outlets. With respect to GreenTech and Croplands Equipment in Australia, I tried to build a bargain-basement SARDI-style head.

    When it wasn’t threatening to tip over, it managed decent coverage over almost 2 meters. Almost.

    As it turns out there’s a very good reason engineers use computational fluid dynamics to design air-assisted sprayers. We were ultimately beaten by an uneven greenhouse floor crowded with obstacles, a stiff canopy of geraniums, and the inverse square law, which states: “The farther away an object is from an effect, the less change can be observed in the object”. This rig now has a new life circulating hot air in a boiler room.

    And I once built an air-assisted, tow-behind sprayer to spray troughs of tabletop, hoop house strawberries. That unit laid down an excellent, uniform spray on all foliar surfaces, but it was frustrating to use. There was almost no clearance in the hoop house, which changed height with the topography, and the alternator couldn’t keep the battery sufficiently charged to run the pump and fans. I felt we could overcome these small difficulties, but sadly the operator ended this experiment halfway through the season. I can only assume the sprayer is now an interesting piece of lawn sculpture.

    This sprayer had potential, but limited resources prevented it from getting beyond the beta stage.

    The Micothon M2

    Despite my inability to build a decent air-assisted sprayer, I have always maintained that air-assist is the secret sauce for efficient, uniform spray coverage. Lucky for me, Great Lakes Greenhouses (GLG) agreed. No stranger to innovation, the company recently purchased a first generation, air-assisted Micothon M2 greenhouse sprayer and invited me to come see it. This was a proper sprayer designed by engineers, and not a delusional plant physiologist, so I was excited to assess and calibrate it. This article will describe what we learned and perhaps in some small way, validate my failed attempts.

    A quick walk around before we got to spraying.

    The M2 features a vertical boom design supported by a portable tender unit, but that’s where the similarities to a classic “tree” sprayer end. Rather than riding on the hot water pipes, or tipping onto two wheels like a hand cart, this version rides on self-leveling wheels. It is drive-assisted but still has to be guided by an operator, like a self-propelled walk-behind lawn mower.

    Drive-assist, self-levelling wheels.

    The mast features 18, three-position nozzle turrets (nine to a side). GLG requested a bespoke spring-loaded break-away section at the top of the boom. This allowed the top nozzles to “duck” under an annoying section of greenhouse infrastructure that would have otherwise prevented it from being positioned between the rows.

    A spring-loaded, break-away boom section (with guard) to prevent impact damage.
    The break-away section in action.

    The air is generated by a centrifugal fan powered by a Honda motor. The air travels up the ducted mast to a manifold of narrow air outlets. When the sprayer is moving, the air outlets precede the nozzles, which initially seemed wrong as the spray would be released outside the air stream. But, upon closer inspection, we saw that the air outlets are not only angled up by 45 degrees but are also angled back so the air can transect the spray.

    Air outlets and nozzles – front view.
    Air outlets and nozzles – side view.

    It was suggested that the blade of air acts like an airfoil, creating an area of low pressure and sucking small droplets into the airstream. This is Bernoulli’s principle and it describes how wings create lift. Personally, I think it behaved more like a Venturi. I’m open to debate since, as evidenced by my attempts at building a sprayer, I’m no engineer. What matters is that we didn’t see any droplets hanging in the air as the sprayer passed. It works.

    Calibration and Optimization

    We followed the same greenhouse sprayer optimization protocol I’ve outlined in this article. Go give it a quick read and come back so I won’t have to reiterate why we took the steps we did.

    Travel speed and air settings

    The sprayer was set to speed “3” of a possible “5”, as recommended by Micothon. Travel speed dictates dwell time, which is the duration the air is focused on the target. Observers stood in the drive alley and in the two adjacent alleys to see how the air moved leaves. The upward angle of the outlets combined with the volume produced by the centrifugal fan wafted and twisted leaves on their petioles. This created sufficient movement throughout the canopy, but not so much that it caused the canopy to louver shut. It was a Goldilocks situation so there was no need to alter anything.

    Preparing to guide the Micothon M2 through the cucumbers under red LED lights. This image gives perspective of canopy height, density and the sprayer clearance.

    Pressure and nozzles

    The tender system regulator was set to 41.5 bar (600 psi) and that pressure dropped to 5.5 bar (80 psi) according to the gauge on the sprayer. While we didn’t test it, I’m certain the pressure at the furthest (aka highest) nozzle would have been closer to 5 bar (~70 psi). With observers in place, we started spraying water using the Albuz 025 (lilac) hollow cone tips.

    We saw the highest nozzle positions were spraying over the canopies and did not need to be on. We also saw drip points form at the tips of the leaves and the bottom of the cucumbers. There was evidence of yellowed (possibly damaged) tissue at the leaf tips, suggesting they were often sprayed to drip. This is wasteful and tends to redistribute deposits in undesirable ways. While it’s hard to avoid on the waxy, vertical cucumbers, it can be prevented on the leaves.

    Note the drip point formed at the bottom of the fruit. This is hard to avoid, but can at least be minimized.

    We turned off the top nozzles, swapped to Albuz 02 (yellow) hollow cones, moved to an unsprayed canopy and tried again. Effectively this was a 20% cut in water and product, but there were no more drips on leaves and less evidence of coalescing deposits. The cucumbers still had drip points, but without an adjuvant that was the best we could do. That’s assuming there would be value in spraying the fruit in the first place – these sprays were targeting the foliage.

    Coverage

    With the subjective part of the assessment complete, it was time to quantify spray coverage. Water sensitive papers were oriented co-planar with the leaves and essentially parallel to the ground. We clipped them 2-3 cm below the leaves by affixing them to the petioles. This way they would move with the leaf and represent a very challenging target (reminiscent of a sucking insect on the abaxial leaf surface).

    This is a difficult target to hit. The spray must get up between the leaf and upper side of the water sensitive paper, which is not in line-of-sight of the nozzle.

    We divided the canopy into quarters, placing one target in each section. This spanned the height of the canopy, but we also positioned them along the canopy depth: One on each of the four plants in the row. This left us with a diagonal cross-section. Read it again – you’ll get it.

    Then we sprayed the row from one side and inspected the results. We saw excellent coverage on the abaxial surfaces of the two plants closest to the sprayer. We expected that. But we were pleasantly surprised to see the spray got in under the umbrella-like leaves and deposited on the adaxial surfaces. This was not line-of-sight for the nozzles, and there wasn’t much room between the paper and the underside of the leaves, so this was clearly the result of air-assisted droplets.

    There was also respectable coverage on the two plants on the far side of the row. These targets were greatly improved once we travelled down that alley and saw the cumulative coverage. This is why you should (almost) never perform alternate row spraying.

    Abaxial side of the water sensitive papers. From left to right, papers ascended from the lower quarter of the nearest plant to the upper quarter of the farthest plant in the row.
    Adaxial side of the water sensitive papers. From left to right, papers ascended from the lower quarter of the nearest plant to the upper quarter of the farthest plant in the row.

    Compared to a tree

    Since I was in the neighbourhood, we decided to see what a conventional, hydraulic tree could do by way of comparison. Frankly, there was none.

    A typical greenhouse tree. Note the 1/4 turn drain near the pressure gauge, the lack of check valves, and the uneven distribution of the nozzle positions (i.e. more at the top) likely intended to direct more flow higher in the canopy.

    The tree was nozzled with Albuz 04 (red) hollow cones angled upwards. There were only a few check valves, so it leaked when it was turned off and had to be drained at the end of each row using a quarter turn valve. Coverage was generally excessive (i.e. coalesced droplets and lots of run-off) and non-uniform (we randomly missed both adaxial and abaxial surfaces).

    Run-off was so pronounced that it washed the dye off the water sensitive papers.

    We re-nozzled to my favourite load out: TeeJet TwinJet fans alternating back and forth by 45 degrees from centre. Using 03’s (blue), we observed improved uniformity, but still saw misses and suspected we were still using too much water. When leaves are drenched they get heavy, causing them to hang lower and obscure the other parts of the plant. This is the contradiction that limits a strictly hydraulic system: Pressure motivates droplet movement, so you need slightly larger drops and more volume. However, too much water causes run-off and weighs leaves down, obscuring the rest of the canopy. Catch 22.

    I proposed getting a set of 02 (yellow) tips in the hopes there would still be enough spray for better uniformity. I hope they tried it.

    A few beefs about the M2

    There’s always room for improvement. Before you think I’m selling these sprayers, here are a few observations from the owners and from what we saw that day. No deal breakers, just some nice-to-haves:

    • The diesel exhaust from both the sprayer and the tender cart is not ideal. Applicators wear respirators, and the greenhouse fans tend to dilute the exhaust, but a battery system (perhaps like a drone) would be preferable to power the drive electrically.
    • There was a latency with the self-leveling wheels and with air build-up in the tower portion of the sprayer. You simply need to be patient before you start down a row.
    • The tower section gets hot to the touch, likely because of the position of the exhaust pipe.
    • The alternator on board recharges the battery, but if you let it sit the battery is depleted (sounds like the same trouble I had with my sprayer, which is somehow gratifying).

    I’m sure you’re asking “How much?”

    Well, at the time of writing, it was almost $70,000.00 CDN, but don’t judge it too harshly! Bear in mind that our assessment saw a reduction of 20% water and crop protection product that would otherwise have ended up on the greenhouse floor. Not only is that a big savings in water and inputs, but it’s fewer refills and it produced far better spray coverage that a hydraulic system. While improved coverage is not always linked to improved efficacy, they certainly go hand in hand. And when we’re considering “softer”, biorational greenhouse chemistries, improved coverage is the best bet we have for pest control.

    All in all, this was an excellent sprayer that I hope is the first of many to grace Ontario’s greenhouses.

    Thanks to Great Lakes Greenhouses for the invitation, and thanks to all the other grower cooperators (names withheld to protect the innocent) that took a risk on building budget, niche sprayers with me. Sometimes, you just have to throw money at it.

  • Canada Gazette Part II – Recent and upcoming changes to Canadian rules for operating RPAS

    Canada Gazette Part II – Recent and upcoming changes to Canadian rules for operating RPAS

    Editor’s Note: This article was posted in June 2025, and as of November 4th all rules have now come into effect.

    Summary

    The Government of Canada introduced the first set of Remote Piloted Aerial Systems (RPAS) rules in 2019, which addressed safety concerns and created a flexible and predictable environment for small RPAS flown within visual line-of-sight (VLOS). On March 6, 2025, amendments were made to the Canadian Aviation Regulations (RPAS – Beyond Visual Line-of-Sight and Other Operations): SOR/2025-70 Canada Gazette, Part II, Volume 159, Number 7. According to the Impact Analysis Statement in the document, the changes:

    • permit RPAS <150 kg to be flown within visual line-of-sight;
    • introduce rules for routine beyond visual line-of-sight (BVLOS) operations for RPAS <150 kg
      • over sparsely populated areas,
      • at low altitudes, and
      • in uncontrolled airspace;
    • remove the requirement for a Special Flight Operations Certificate (SFOC) for these operations;
    • include requirements for
      • new pilot certification,
      • new technical standards for the aircraft and supporting systems,
      • new operational procedures, such as increased distances from airports, heliports, and people, as well as
      • new requirements for individuals and organizations to operate BVLOS.

    In addition, the Regulations will update existing service fees and introduce fees for existing services that are currently provided for free and the new services that will be provided to the RPAS sector.

    These regulatory changes are driven by agriculture, but also increasing utility in package delivery, use in emergency response (e.g. fire assessment), environmental impact assessment and infrastructure inspection.

    The original document is lengthy, so only those changes that relate to the use of spray drones are reproduced here. For more details, refer to the Regulations Amending the Canadian Aviation Regulations (RPAS – Beyond Visual Line-of-Sight and Other Operations) Canada Gazette, Part II, Volume 159, Number 7. Transport Canada has a summary of the changes here.

    At the time of writing, there are no agricultural, terrestrial pesticides registered for application by RPAS in Canada. Health Canada’s Pesticide Compliance Program (PCP) is responsible for promoting, monitoring and enforcing the Pest Control Products Act (PCPA). Their factsheet can be downloaded here.

    Objectives

    There are three objectives to the new regulations:

    • Regulatory predictability, economic growth, and innovation
    • Safety risk mitigation
    • Fee modernization

    The regulations build upon Part IX of the CARs and introduce new requirements to reflect the increased risks of the two new categories of operation:

    • Medium drones that weigh above 25 kg up to and including 150 kg flying within VLOS near and over people, in both controlled and uncontrolled airspace; and
    • Drones that weigh 250 g up to and including 150 kg flying BVLOS in unpopulated and sparsely populated areas, below 400 feet above ground level, and in uncontrolled airspace.

    Grouping the new regulations – The 3 P’s

    The new regulations can be grouped into:

    • Pilot (pilot training and certification)
    • Product (aircraft and supporting systems)
    • Procedures (operational rules)

    In addition, there are new requirements for individuals and organizations operating BVLOS, such as appointing an accountable executive, and requirements to establish training programs and risk management processes, which are discussed in more detail below. These new requirements will allow for clearer organizational oversight with larger-scale operations, covering larger geographic areas, as well as an increase in the number and types of drones being operated.

    The Pilot

    Advanced Pilot Certificate

    TC has determined that the following operations may be added to the types of operations conducted by Advanced Pilot Certificate holders, without the requirement to obtain a new pilot certificate:

    • VLOS operations with a medium-sized drone (above 25 kg up to and including 150 kg).
    • Extended VLOS operations (EVLOS), using a visual observer to scan the airspace.
    • Sheltered operations, which allow the drone to be flown around a building or structure without the use of a visual observer.

    Advanced Pilot Certificate operators will be required to pay fees associated with the obtaining the certificate:

    • $10 exam fee, paid to the Government of Canada (GoF).
    • $25 certificate issuance fee, paid to the GoC.
    • $257 flight review fee, paid to the flight reviewer.

    Pilot Certificate for Level 1 Complex Operations (Lower-risk BVLOS)

    The Regulations will introduce a new pilot certification process for lower-risk BVLOS called Level 1 Complex Operations. A pilot must be at least 18 years old and have their Advanced operations certification.

    • Pilot must attend RPAS training (“ground school”).
    • Pilot will need to pass a new online multiple-choice exam delivered through TC’s DMP.
    • Pilot will need to visit a flight reviewer to do an in-person flight review.

    Every two years, pilots will need to do at least one training renewal activity recognized by TC (e.g. flight review, training activities, or retaking one of the pilot exams in the DMP.)

    CARs 901.19, Fitness of Crew Members, and the requirements of the RPAS Operator Certificate (RPOC) provide sufficient mitigations to maintain safety within the level of risk for BVLOS operations. However, a medical standard for operations outside the lower-risk category may be considered in future regulatory work.

    Commercial RPAS operators will need to hold a Level 1 Complex Certificate to conduct lower-risk BVLOS operations. To receive their Level 1 Complex Certificate, operators will need to pay a certificate fee of $125 to TC.

    Advertised Events

    Part IX of the CARs requires operators of RPAS of at least 250 g to obtain an SFOC to operate at an advertised event, which is defined as “an outdoor event that is advertised to the general public, including a concert, festival, market or sporting event.” The Regulations will expand this requirement to all RPAS, including microdrones weighing less than 250 g.

    The Product

    Drone registration is expanded to all drones 250 g and above.

    Declaration

    A drone won’t be permitted to fly in an operating environment unless the manufacturer supplies a Declaration (online form, Standard 992) or a Pre-Validated Declaration (PVD) for that respective operating environment. Operating environments include medium-sized drone in controlled, or uncontrolled airspace, or away from people, or BVLOS operation away from populated areas below 400 ft and in uncontrolled airspace.

    The PVD is a two-step process where the plan for the aircraft design is submitted in the context of Standard 922, and when approved, then they complete the Declaration. Operating environments include VLOS with medium-sized drones near and over people, and certain BVLOS operations over sparsely populated areas, below 400 ft and in uncontrolled airspace.

    Maintaining a PVD requires annual reports of the estimated number of flight hours, a description of any safety-related issues, and any relevant design changes.

    The Procedures

    Advanced Pilot Certificate holders can perform Extended VLOS (EVLOS) operations and sheltered operations if:

    • The drone is within a certain distance from the pilot, while a second person with a Basic Pilot Certificate scans the airspace and notifies the pilot of any other airspace users or hazards.
    • Performing a sheltered operation, the pilot may fly their drone around a structure without keeping the drone in direct line-of-sight, if they keep the drone within a certain distance to the structure (intended for building inspections).
    • The Regulations increase the minimum distance from people not involved in the operation and require additional planning considerations such as weather conditions that could affect the pilot’s ability to maintain line-of-sight.

    Lower-risk BVLOS

    Pilots will need to remain in uncontrolled airspace away from aerodromes, below 400 feet, and over unpopulated or sparsely populated areas (i.e. <25 people/km2 per Stats Canada and the Drone Site Selection Tool.

    RPAS Operator Certificate (RPOC)

    The new RPOC focuses on risk management and addresses the trend of larger fleets, longer flight times and BVLOS operations. The RPOC is an assurance there are policies and procedures in place that reflect the size and complexity of the operations. It is a Declaration to TC that the pilot or organization meets requirements in CARs (via the DMP) and there is no requirement for renewal.

    Fees for services

    Basically, the RPAS Operator Certificate fee is $125 CDN with the goal to lower the cumulative cost of BVLOS. The SFOC structure, which originally proposed two steps (Low-Complexity and High-Complexity) now has two new categories: Very-Low and Medium Complexity. Fees were revised to reflect the different levels of complexity and the related levels of effort that would be required by TC. These fees will be adjusted for inflation.

    Fines (Administrative Monetary Penalties)

    Under the Aeronautics Act, the Minister of Transport has the authority to issue administrative monetary penalties (AMPs) to anyone who violates designated provisions of the Act and the CARs. Most of the provisions in Part IX of the CARs are enforced through the assessment of AMPs imposed in accordance with sections 7.6 to 8.2 of the Act, which carry a maximum fine of $5,000 for individuals and $25,000 for corporations and include the potential suspension or cancellation of a person’s Canadian Aviation Document.

    When do the new regulations come into force?

    New regulations will be introduced in stages to give stakeholders the opportunity to become certified and to familiarize themselves with the new requirements before the 2026 season. Some regulations will come into force on April 1, 2025, but others will activate when they are published in the Canada Gazette, Part II, including:

    • the ability to register drones
    • submit declarations and take new pilot exams

    The remaining provisions will come into force on November 4, 2025, such as:

    • provisions relating operating medium-sized drones in beyond visual line-of-sight (BVLOS) in lower-risk environments.

    For more information, see the Regulations Amending the Canadian Aviation Regulations (RPAS – Beyond Visual Line-of-Sight and Other Operations) Canada Gazette, Part II, Volume 159, Number 7.

    Also see this short-and-sweet summary from RealAgriculture.