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Evaluating the return on investment of optical sprayers for horticulture
Investing in an optical sprayer for horticulture is not a straightforward financial decision. Compared with a conventional boom sprayer, the upfront capital cost is substantially higher, often by an order of magnitude, and most commercial systems require an annual software or service subscription to operate. Despite these barriers, adoption is accelerating, and many growers who have made the investment report very positive outcomes.
To help clarify when and where this technology makes financial sense, I developed a calculator to estimate the return on investment (ROI) of optical sprayers under a range of production scenarios. The goal of this tool is not to promote the technology, but to provide growers and advisors with a structured way to evaluate whether it fits their specific operation.
Note: This calculator was designed for onion and carrot production in Ontario, Canada. Model parameters can easily be adjusted reflect other production systems. However, if you need assistance making these changes you can contact me by email.
New versions may be uploaded as the calculator evolves through experience and based on user feedback, so check back. You can download Version 1.1 (April, 2026), HERE.
How to use the calculator
At first glance, the calculator may appear overwhelming because it requires a fair amount of information to be entered. This is the minimum data required to reflect real-world conditions while avoiding an oversimplification that could lead to misleading conclusions. Cells shaded in yellow are meant for user input. All other values are calculated automatically based on those inputs.
For convenience, the calculator is pre-filled with generic values derived from grower discussions and informal benchmarks. These default numbers are meant only as placeholders and to provide general reference. They are not sufficiently accurate on their own to support financial decisions.
Users should replace all default values with operation-specific data whenever possible. As with any economic model, the quality of the output depends entirely on the quality of the inputs.
The calculator is organized into three spreadsheets (see tabs at bottom).
1. Introduction
This tab provides general instructions and contact information. No data entry is required.
2. Sections Explained
This is a reference tab that explains each section of the calculator in detail. It is intended to help users understand how different inputs affect the results and the intention of each section (small table) withing the sheet. No values should be entered here.
3. Calculation Sheet
This is the main working tab. All data entry occurs here. To prevent accidental changes that could break formulas, the sheet is protected. For most input fields, a brief explanation is provided immediately to the right of the cell. In the results section, short interpretations are often included, such as: “Decrease of 36% ($101,250/year) in hand-weeding cost with optical sprayer.” Within this tab, scenario tables are also provided. These tables are designed to illustrate how different acreages of the two crops analyzed affect each of the calculated financial indicators.
Insights from scenario testing
Even using rough approximations, several consistent patterns emerge from adjusting the calculator inputs:
Herbicide savings alone rarely justify the investment
In high-value horticultural crops, herbicide costs are often a relatively small portion of total production costs compared with labor, equipment, and the overall value of the crop. In many cases, any reduction in herbicide expenditure is largely offset by increased tractor hours resulting from slower operating speeds and narrower effective spray widths typical of optical sprayers.
Labor savings can be decisive
When the technology results in meaningful reductions in hand-weeding, the financial impact can be substantial. This is especially true in crops such as onions, where hand-weeding is both costly and difficult to source reliably. In these situations, labour savings alone can drive a favorable ROI.
Yield protection may outweigh cost savings
Several growers report stand losses and weakening associated with herbicide phytotoxicity as a major production risk. By limiting spray exposure to crop plants, optical sprayers can significantly reduce or even eliminate this issue. In high-value systems, relatively small yield gains resulting from improved crop safety can translate into revenue increases large enough to justify the technology, even if other savings are modest.
Scale matters
When evaluating advanced sprayer technologies, scale becomes a decisive factor. The high capital investment and ongoing service fees may be difficult to justify for small, and in some cases, even medium-sized operations.
What about herbicide resistance?
The long-term implications of optical sprayers for herbicide resistance management are still uncertain. Recent research from the University of Arkansas has raised concerns in field crop systems, suggesting that poorly optimized optical spraying can result in short term gains, but these can be outweighed over time by higher weed escape rates compared with broadcast applications. If these escapes are allowed to grow and set seed, rapid seedbank replenishment and accelerated resistance development may occur.
This highlights an important limitation of short-term ROI calculations. A single-year economic benefit may look attractive, but if the system allows even a small number of weeds to consistently escape and reproduce, the long-term consequences can be severe.
On the other hand, optical sprayers may eventually enable new resistance-management strategies. It is possible that new active ingredients, higher labelled rates, or novel use patterns could be registered specifically for targeted spraying in horticultural crops that would not be feasible with broadcast applications. Such developments could significantly improve resistance management tools. As always, it is essential to remember that the label is the law: only registered products and rates may be used, regardless of perceived crop safety.
ROI implications beyond herbicide spraying
Optical sprayers can deliver value beyond herbicide applications, even though weed control is their primary use. These additional uses may improve overall ROI. However, because their economic impact is still difficult to quantify, they have not been included in the calculator.
Depending on the model, additional value-generating capabilities can include:
- Creation of weed maps: Some systems can generate weed maps automatically while spraying, at no additional operational cost. These maps can support future management decisions.
- Application of fertilizers and other pesticides: Although optimized for herbicides, optical sprayers may also be used to apply other inputs, such as fertilizers or non-herbicide pesticides.
- Crop thinning: Certain manufacturers have developed algorithms for automated crop thinning, particularly in crops like lettuce.
Conclusion
Even using approximate inputs, it is clear why optical sprayer adoption is expanding rapidly in Canada.
- For medium to large-scale operations, the ROI can be highly attractive, and the range of potential benefits continues to grow.
- As the technology matures, more equipment options are emerging to serve a wider diversity of crops and farm sizes.
- Manufacturers are introducing wider and more flexible platforms, and Ontario-based companies are actively developing alternative machines and service-based business models that may better suit smaller operations.
It is difficult to argue that optical spraying is a passing trend. While it’s not a universal solution and must be implemented carefully, the technology is clearly here to stay. It will reshape weed management and production economics over the long term.
January 16, 2026
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.
December 8, 2025

Comparing Fluorescent Dyes for Spray Coverage Evaluation

I work in agricultural extension and I’m always on the lookout for new methods to help me achieve my goals. A big part of my job is to research and teach efficient, effective and safe crop protection practices, so it follows that I have to be able to evaluate the quality of a spray application. Fundamentally, there are two ways to do it:

Wait to see if the pesticide did its job and protected the crop from weeds / bugs / disease.
Don’t wait. Confirm your spray is depositing where you want it before committing to the application.

Three guesses which approach I advocate. So, how do you check spray coverage in a way that’s quick, cheap, easy and informative? Again, there are choices, but rather than simply list them I’ll add a little insight in the form of pros and cons.

Method	Pros	Cons
Water sensitive paper	Relatively cheap, available, clean, easy, repeatable, supports a photographic record, simple to analyze.	Does not accurately reflect coverage on plant surface, slow to place and retrieve, can be spoiled by dew, humidity and physical contact.
Inspecting for residue / wetness	Cheap and fast.	Not proactive, too subjective, not repeatable, pesticide many not leave visible residue, requires re-entry soon after spraying.
Inspecting spray pattern (e.g. shoulder check)	Cheap and fast.	Not proactive, not indicative of coverage, not repeatable.
Watching for run-off	Just don’t.	Just don’t.
Fluorescent dyes	Reflects actual, whole-canopy coverage and off-target coverage at same time.	Expensive, hard to find, messy, time-consuming, hard to photograph, not repeatable, leaves unwanted residues (or can’t be used on edibles), may have to take place at night, may fade quickly… *or is any of this actually true?*

I’ve never been a proponent of spraying dyes because of the reasons I listed in the table. If I already have difficulty convincing a grower to leave the sprayer or tractor cab to place and retrieve water sensitive papers, what are the odds of them mixing a messy and expensive tank of dye and waiting until twilight to see the results?

On the other hand, dyes are compelling. Particularly if we change the perspective a little. What if we consider the use of dyes, not as a tool for a grower, but as a tool for agricultural extension or consultation (really, anyone that wants to research or teach the safe and effective use of crop inputs)? Several of the cons are minimized or even eliminated. Additionally, this new lens reveals several uses for dyes beyond spray coverage. This is not an exhaustive list:

Off-target (primarily drift) evaluation
Dermal exposure / PPE evaluation
Rinsate / sprayer cleanout evaluation
Sprayer loading / point source contamination evaluation

I decided to compare a few of these dyes. I enlisted the help of a local blueberry operation. Being October, all the berries have been picked so we could spray the bushes without any risk to the fruit. Plus the sprayer was clean and the growers were curious to evaluate their spray coverage.

Having secured a location, spray equipment, and operator, I needed dyes and some criteria for choosing them. First and foremost, I chose fluorescent dyes that glowed under UV (aka black lights). My thinking was that they would be more interesting in demos, and given that we might be spraying horticultural operations, I didn’t want obvious and persistent stains on the produce. At least not something easily seen in daylight before it broke down and/or was washed away.

My UV dye candidates had to be:

Moderately inexpensive.
Non-toxic (i.e. had an SDS that clearly permitted human exposure, were environmentally friendly and could be sprayed on edible crops).
Readily available in Ontario (e.g. quickly and cheaply shipped from within Canada or perhaps the US).
Available in formats that facilitated small volume batches (anywhere from 50 mL squirt bottles for indoor demos, up to 50 L volumes for field demos).
Clearly visible on plant tissue.

I found five likely prospects for the study. I won’t list prices, but none of them were over $100.00 CAD. Number 3 was a free sample and number 5 was gifted to me by a colleague more than 15 years ago. I looked up the SDS for that last one and was surprised that it was relatively inert. So, I used it.

Dye number	Name of dye	Commercial size	Manufacturer	Location
1	IFWB-C81PT	1 pint	Risk Reactor	California, USA
2	UVTRACER-G1PT	1 pint	Risk Reactor	California, USA
3	Eco Pigment Blaze Orange SPL15JX	Sample size – 100 grams	DayGlo	Cleveland, Ohio, USA
4	Fluorescent Yellow Tempura Paint	1 liter	Tri-Art Manufacturing	Kingston, Ontario, CA
5	Phosphor Powder (Zinc Orthosilicate: Manganese CAS#11-47-2)	1 kg	Global Tungsten and Powders Corp.	Pennsylvania, USA

I also purchased UV lights. When I was bequeathed the phosphor powder it came with heavy, ancient, black lights. They made an unsettling humming noise and required a power source, making them unwieldly for field work. I opted to try three battery powered versions instead. Again, I won’t list prices, but they weren’t unreasonable.

UV flashlight number	Name of light	Manufacturer	Wavelength / wattage	Batteries
1	Super Tac	Risk Reactor	395 NM / 850 µW/cm² at 5 inches	Rechargeable battery provided
2	Mini Zoom	Risk Reactor	395 NM / 1 watt	1 AAA
3	V3 UV Flashlight with 68 LEDs	Amazon.ca	395 NM / 10 watts	3 AA

Regarding the recipes, one of my criteria was that the dyes could be mixed in relatively small batches. I chose 50 L as the high end because the airblast sprayer we were using (Turbo-Mist 30P) could still prime when only 50 L was added to the tank. This allowed us to mix as small a batch as possible, while still having enough to spray a row of berries from both sides. We left three rows between treatments to serve as buffers.

Turbo-Mist Model 30P before the dye-job.

I also had to consider the nature of the dyes. The Eco Pigment (Dye 3) is a hydrophobic powder and two colleagues warned me that it was notorious for plugging filters. So, it had to be mixed with a non-ionic surfactant (NIS) to help “wet” the powder prior to adding it to the tank. In fact, NIS seemed like a good idea for all my dye candidates, so I included Activate Plus (Sollio Agriculture, Winfield Solutions) in each recipe.

I added the dye, NIS, and a small amount of water to a Pyrex measuring cup on a digital scale, then rinsed the cup into a final volume of 50 L while filling the tank. I didn’t always follow the advice I received, so I’ll show you the ratios I was told and (right or wrong) what I ultimately did.

Dye number	Manufacturer- or colleague-suggested ratio	Amount of dye	Amount of NIS	Amount of water
1	1 part dye : 10,000 parts water	125 mL	65 mL	310 mL
2	1 part dye : 10,000 parts water	125 mL	65 mL	310 mL
3	1 gram dye : 1 mL NIS : 200 L water	65 grams	65 mL	425 mL
4	1 part paint : 100 parts water	500 mL	65 mL	0 mL
5	1 gram dye : 1.25 L water	65 grams	65 mL	425 mL

It took roughly 15 minutes to fill, prime, spray, and rinse out each dye. We started at 5:00 p.m., were done at 6:15, and then waited for sunset at 7:30.

50 L tank mixes going through circulation and paddle agitation.

Draining the remains and rinsing the tank. It looks terrible, but these dyes are intended for environmental projects like tracing water courses.

We used a smartphone (Google Pixel 9a – 48 megapixel camera) to photograph each combination of dye and flashlight. It was tricky to find an angle where the black light illuminated the residue, but didn’t wash out the photo. In those cases where the dye was evident, it was always far more vibrant in person than through the lens of a camera. As for the results?

Lets start with the lights. We found that the high wattage of Light 3 showed dye more easily. This also happened to be the cheapest light, which was a pleasant surprise.

Dye 1 and 2 were disappointing. We couldn’t see anything on the plants. This dye is intended for monitoring plumbing and water courses, and the manufacturer states that the colour will disappear if the solution is mixed with chlorine. Perhaps mixing it with city water caused it to fade, but that’s likely to happen, so these dyes failed.

Dye 1 – Light 1, 2 and 3. A sad, single drop showed up for Light 3.

Dye 2 – Light 1, 2 and 3. Again, a solitary deposit illuminated under Light 3.

Dye 3 was spectacular. Not only was it evident with every light source (including day light to some extent), but we were able to find it several rows downwind, on the sprayer nozzles, all over the tires and on the floor of the cab (which surprised the operator). I may have mixed this one too strong; It seemed to clump on the leaves, but perhaps that’s because they were exceptionally waxy.

Dye 3 showed up everywhere… whether we wanted it there or not.

Dye 4 came in second place. It wasn’t amazing, but it was visible. This is children’s tempera paint, used in daycares for finger painting and at universities for raves. I’ve used it in the past with mixed results, not only to spray canopies, but in classroom demos on cabbage leaves and as a surrogate tracer to hunt down where pesticide hides in sprayer plumbing. It’s OK in a pinch if you mix it at least 2x more concentrated than I did here.

Dye 5, like dyes 1 and 2, was a disappointment. I’ve seen it used in powder-form to demonstrate how dermal exposure can spread as you touch clothing, doorknobs, your face, and places where the occasional adjustment is required. But in a liquid solution, it wasn’t any good at all.

Persistence

We followed up after the application to see if the dyes would persist. Twenty four hours after application, Dye 4 (our runner-up) was gone. This was no surprise given it was a water soluble paint and wasn’t terribly showy to begin with. However, Dye 3 (our winner) was still clearly in evidence. This is a hydrophobic, micro ground powder (~0.1 micron). That’s one reason it had to be mixed with a non-ionic surfactant. The following photos shows little or no change after 24 hours and a respectable dew:

Three days after application (DAA), we had a rain event. Four DAA this (blurry, sorry) image was taken:

We see that the deposits did redistribute to drip points and the overall coverage was reduced, but it was still holding on. This means it likely shouldn’t be used on any horticultural crop that isn’t going to be washed. Or at least used long before any fruit, leafy green or vegetable contacted by the powder will be harvested. Not because it is unsafe (see safety data sheet) but because of the optics to buyers.

Conclusion

And so, I hope you have been inspired by this process. I’ve learned that the use of dyes for education and research is potentially powerful, relatively cheap, and more accessible than I originally thought. Certainly the growers were impressed by what they could suddenly see and it’s led them to reassess some of their practices. Just bear in mind the possible persistence, and remember to wear gloves when mixing.

Thanks to Mark Ledebuhr, Helmut Spieser, David Manktelow, and Ben Werling for the helpful advice. Thanks to Brandon and Jordan Falcon for use of their spray equipment and their blueberry operation.

October 2, 2025

Ecorobotix’s ARA Sprayer: A targeted sprayer that’s finding its place in Ontario vegetable fields
Targeted spraying is a technology that enables the site-specific application of plant protection products and liquid fertilizers based on sensor readings. Some of the latest machines incorporate computer vision and processing capabilities that can distinguish between different types of weeds and crops based on multiple adjustable criteria.
The Swiss-made ARA Sprayer by Ecorobotix, has recently generated significant interest among Ontario growers. This article provides a technical overview of the machine, including a detailed explanation of its main features and capabilities.
The Sprayer
The sprayer is a two-component system, mounted directly onto the front and back of a tractor. The front unit consists of two separate tanks: one dedicated to the chemical solution and the other to fresh water, which can be used for rinsing or refilling the chemical mixture tank. The front component also includes the pump and processing unit (Figure 1).
Figure 1- Front-mounted unit.
The boom section is mounted via three-point hitch to the rear of the tractor (Figure 2). The shrouded boom folds for transport and storage and features 156 individually controlled nozzles (Figure 3).
Figure 2- Rear unit deployed.
Figure 3- Closeup of the boom.
The unit can be controlled and monitored from a tablet or smartphone connected through the machines’ own Wi-Fi. External data connection through internet is only required for occasional maintenance and updates but not for regular field operations. Regardless of the complexity embedded in the smart operating system, the interface is intuitive and easy to manage. Most of the parameters are automatically optimized by the software (Figure 4).
Figure 4- Tablet interface.
Capabilities
Since the intelligent vision system acts as the central controller for each individual nozzle, it enables a wide range of operating modes and potential applications. Depending on user needs, the system can process information and respond in various ways. The following list outlines the currently available and tested features, which may be expanded in the future.
Banded Spraying
In this mode, parallel bands of variable width are sprayed, which might include or exclude the crop (Figure 5), depending on the objective. The lines are defined based on AI detecting a planting pattern, which will lead to the automatic definition of the spraying swaths.
Figure 5- Banded application options: in-row or inter-row.
Size-Exclusive Spraying
This option allows targeting the spray based on the plant size. It can either be used to:
- Detect and spray weeds larger than a small emerging crop.
- Detect smaller emerging weeds in an advanced-stage crop. Weeds similar in size or larger than the crop will be missed in this case. (see figure 6 – left).
- Spray only the crop with fertilizers or pesticides when no-specific algorithm has been developed to differentiate it from the weeds. The crop must be significantly larger or smaller than the weeds for this mode to work efficiently. (see figure 6 – right)
Figure 6- Only plants smaller (left) or larger (right) than a specified target are sprayed.
Green on Brown Spraying
The machine will spray all detected green material (Figure 7). This is particularly useful for improving chemical use efficiency in stale seedbed and insecticide applications. It also offers an interesting option to reduce the risk of herbicide carryover in pre-plant, post-weed-emergence control, especially when weed cover is low and the product may persist in the soil long enough to affect the crop.
Figure 7- Green on brown spray.
Green on Green Spraying (Six Scenarios)
The vision system and processing capabilities can identify the crop, distinguish it from weeds, and selectively target either, regardless of plant size. Additionally, a variable safety buffer can be defined to determine how close a spray can be applied to the nearest crop leaf. If this feature is inactive, any overlapping weeds will be sprayed, even if the herbicide contacts the crop. If active, the sprayer will avoid targeting weeds that are closer than the defined safety buffer distance, which can be set up to 16 cm (6.3”).
The parameters can be configured to cover six difference scenarios:
1. Selective herbicides when no safety buffer is required
All weeds will be sprayed, regardless of their proximity to the crop. If they’re very close, the crop might receive part of the spray (Figure 8). This mode is suitable for selective herbicide applications.
Figure 8- Herbicide application with zero safety buffer.
2. Non-selective herbicides when the contact with crop canopy should be minimized
In this case, depending on the potential damage caused by the chemical contacting the crop, a variable buffer can be programmed. Only weeds that can be sprayed while maintaining the defined buffer distance from the crop will be targeted (Figure 9). Inevitably, weeds in very close proximity or overlapping with the crop will be missed.
Figure 9- Weed target spray with a safety buffer.
3. Crop-targeted spray
The machine will detect the crop and will not spray anything else (Figure 10). This can be useful for insecticide or foliar fertilizer applications.
Figure 10- Crop-targeted spray.
4. Application of weed pre-emergence herbicides post-crop-emergence
In this case the entire surface, except the crop canopy is sprayed (Figure 11). It can be utilized to spray herbicides with soil residual activity post crop emergence.
Figure 11- Pre-emergent herbicide application excluding the crop/
5. Monocots vs dicots weeds differentiation
This mode is limited only to onion fields for now. It can be configured to spray only monocots weeds (grasses, sedges) or only dicots weeds (broadleaf). This can be useful to increase the efficiency of post-emergence broadleaf or grass selective herbicide applications.
6. Specific weeds targeted
In this mode only the target weeds will be sprayed. As of now, it’s only available for thistles, docks, and common ragwort. It can be used when a specific herbicide is used to target hard-to-control species.
Speed and Accuracy
For all applications, the company claims to have a spray accuracy of 6 cm by 6 cm (2.4”x2.4”). The speed of operation will be dependent on the weed size. The larger the weed size, the lower the recommended speed to allow for an optimal spray coverage of the weeds, increasing the treatment efficacy. The speed operating range is 0 to 7.2 km/h (0-4.5 mph).
Weed coverage or density does not affect the maximum recommended speed, as the machine can process images at such high rates that it is capable of scanning and spraying 100% of the area when moving at full speed. In other words, the processing unit does not need to slow down to detect, differentiate, and target weeds, even when they are present at very high densities.
Ecorobotix claims the machine can cover 2.8-3.2 ha (7-8 acres) per hour under typical conditions and can run 24/7 independent of light conditions.
Crop Portfolio
As of August 2025, the company has developed the following algorithms for specific crop recognition:
Vegetable Crops:
- onion
- carrot
- lettuce
- endive/chicory
- beans
- spinach
- broccoli (beta)
- cauliflower (beta)
- leek (beta)
- other cabbages (beta)
- potatoes
- sweet corn
Field Crops:
- sugar beet
- rapeseed (canola)
- corn
- soy (beta)
- cotton (beta)
- wheat (beta).
For the crops not listed, the equipment can still be used but not with the features that required crop identification for targeted sprays.
Technical Specifications
- Minimum weed size required for weed detection: 4 x 4 mm.
- Maximum plant height: 40 cm.
- Minimum crop size for proper identification: at least two true leaves.
- Minimum tractor power: 90 HP
- PTO: 540 RPM, 4 HP (3 kW) max
- Three-point hitch: cat 2 front and back.
- Weight:
  - Front unit: 705 lb or 320 kg (empty), 2,645 lb or 1,202 kg (full)
  - Rear unit: 2,257 lb or 1025 kg
- Dimensions (Figure 12):
  - Front unit: 5’7” x 4’7” x 5’7” (W x D x H)
  - Rear unit: 21’4” x 8’10” x 4’3” (W x D x H)
Figure 12- Dimensions.
Cost of Purchase and Operation
At the time of writing, the purchase cost for a complete unit is around $300,000 USD, depending on the algorithms purchased and shipping fees. In the following years, there is an annual fee associated with the operating system maintenance and development. The basic subscription includes algorithms for three crops, as well as access to all beta-stage models currently in development. Additional crop algorithms can be purchased. For accurate pricing, contact their Canadian partner, Univerco.
According to the manufacturer, the equipment does not require regular replacement of expensive components beyond standard sprayer preventative maintenance. While some components are standard and readily available, the company also keeps a regular stock of specialized parts at its warehouse in Pasco, WA, available for immediate shipping. Comprehensive service and maintenance support is provided locally by Univerco.
Testimonial
Wendy Zhang is the head agronomist for Keejay farms. She oversees more than 5,000 acres of diverse vegetable crops, predominantly carrot and onions. In her own words, the machine is “easy to operate, very accurate, and fast enough for a large-scale farm.” She also highlighted substantial savings on chemicals and the significant advantage of being able to safely spray close to the crop using products that cannot be broadcasted due to the risk of unacceptable crop damage.
The most important benefit, she says, is the ability to apply treatments very close to the crop canopy, using effective rates and chemistry without compromising crop safety. No other practical tool offers this capability. A clear demonstration of its effectiveness is that no other spray equipment is currently being used for their large onion operation.
The Grower Magazine published an excellent article about this machine, featuring other grower testimonials.
Thanks to Olivia Soares de Camargo, Business Development Manager at Ecorobotix, for providing much of the information used in this article.
August 26, 2025