Category: General Operation

All general hort articles on sprayer operation.

  • Working with an Arborist: Drive-Along Diaries #1

    Working with an Arborist: Drive-Along Diaries #1

    April 23rd, 3:45 am

    I was excited. Today would be my first in a series of drive-along experiences with Ontario sprayer operators. However, to get from my home in Southwestern Ontario to Newmarket, I would have to cross Toronto. This is not my favourite thing to do. But, Dean Solway, Plant Healthcare Supervisor with Shady Lane Expert Tree Care, was based out of Mount Albert and he liked to start at 6:00 am. So, a hot shower and a hot coffee (not necessarily in that order) gave me the emotional support I needed to throw elbows on the parking lot we call the 401.

    It was strangely unsettling to see Tim Horton’s closed, and equally odd to see only a handful of cars on the highways. That may have been the fastest, smoothest drive through Toronto that I’ve ever had.

    5:45

    I arrived at the 10-acre lot that has been owned by the company for the last 45 years. I walked past a small, 500 tree nursery they’d recently planted to find Dean in the office. He was busy checking bookings for the day and assigning jobs to his three Plant Health Care trucks (PHC1, 2 and 3). More on those later. After a few introductions, I faded into the background and let them get on with things.

    Dean was ensuring the routes made sense and that everyone was ready to go. He explained that the week’s bookings were set each Friday, but that things could always change at the last minute. Front-line administration would handle client calls and communicate with the trucks throughout the day. They also ensured the clients were given at least a day’s notice that someone would be coming to treat their plants. Interestingly, the company is also required to inform the client’s neighbours. Dean said it helped avoid potential conflicts such cars, sunbathers or laundry left in the path of potential overspray. Not that such things ever happen, of course.

    Operators kept referring to “The Board” which showed their daily assignments. With 2,800 clients scatted over Brechin, Barrie, Oakville, Pickering, Oshawa and downtown Toronto, thoughtful planning and clear communication were critical requirements.

    I eavesdropped as Dean talked to a new hire about safety. Filter checks/replacements, face shields, gloves and orange vests were assigned, and I’m confident that it wasn’t staged for my benefit. Operator safety was a theme that came up throughout the day and it was clear Dean took it seriously. As the trucks got ready to roll, he fielded random questions about pesticide rates, tank mixes, crop staging and general agronomy as he double-checked that each truck was properly loaded.

    I learned that standard operating practice was to regularly test the equipment and plumbing in each truck. Experience showed it was easier and less contentious to deal with minor leaks and similar issues in the yard than on a Toronto highway or even worse, at a client’s home. That took us outside.

    6:15

    Each truck was equipped with a tablet containing SDSs for all the products they use, PDFs of the pesticide labels and a hyperlink to Health Canada’s Pesticide Label Search website. Many of the products used by arborists are biorational / organic, either by choice or because labels do not permit the use of many conventional pesticides in urban environments. I felt a bit of team-pride when I was told that OMAFRA’s Pub 840 is a significant reference document for the company.

    As he checked the trucks, Dean noted that it was important to explain to clients that eradicating pests isn’t always possible. Most often it’s about maintenance. For example, today would predominantly be about fungicide applications. Ornamental fruit trees such as crab apple were at risk of scab infection and the window for protection was narrow. Far be it for me to bring up climate change, but Dean did mention that this was the earliest he’d had to apply these products in nine years.

    Protectant fungicide treatments need time to dry to be effective. If it were to start raining steadily inside two hours following the application, Dean said the client would be eligible for a re-application ASAP. According to OMAFRA Publication 840, four applications were permitted for this chemistry, and clients were scheduled to receive three at regular intervals over four weeks. That gave time for the applicator to rotate back around, and it left capacity for a possible re-application if required.

    Incidentally, I am a master of foreshadowing.

    The Trucks

    PHC1 and PHC2 were designed to apply plant protection products. PHC3 was strictly for fertilizer and carried an extra 450 L just in case it was needed throughout the day. To remain flexible and efficient, the fertilizer applicators had to be able to take advantage of opportunities if the schedule changed. Returning to reload would be a big loss of productivity, so a little extra onboard was reasonable insurance.

    Dean explained that all the trucks were filled either the morning of, or the night before, depending on the product. In the case of compost tea, it’s a three-day process that requires a lot of planning. It must be applied at less than 50 psi to prevent mechanical damage to the living component of the mix. It can be applied to the soil or as a foliar treatment.

    We’d be riding in PHC1, which had a single tank subdivided into four separate 170-gallon tanks. The reel was a 60 amp electric auto reel with 300 feet of high-pressure hose. The pump was an AR 813 diaphragm pump, and the motor was a 20 hp twin cycle Vanguard and capable of producing up to 300 psi which is sometimes needed to reach the tops of the highest trees. Dean helped design this system himself and grinned when he said that even as low as 150 psi, you can feel the pistol “kick” in your hand.

    Speaking of which, the hose terminated in a quick-connect that allows the operator to swap between a pistol for nearby targets, and a long-barreled rifle for more distant targets. There was also a manually pressurized two gallon bottle sprayer for when the hose-and-gun assembly simply wouldn’t reach.

    The last thing Dean checked was that each truck had cleanup equipment, including detergents for any overspray accidents. He explained that most clients want no sign of the trucks coming, going, or having ever been there. That might mean washing away speckles on cars and windows, or marks from the hose being dragged on stonework or past beds and gardens. I’ll share my observations on how urban spraying seems to be viewed by the general public later on.

    6:45

    We’re on the road, passing through Newmarket in the York Region before slipping into stop-and-go traffic on the 404. We aren’t five minutes out before Dean’s phone rings. PHC1 is essentially his office, and he remains in communication via a work phone and headset, relying on a dedicated GPS to guide him from client to client… when the maps are accurate, anyway.

    As we drive, Dean notes that rain is forecast so we’ll do as much as we can. He’s set up a linear route going to the furthest client first and working our way back. That way, if it does rain, it will be easier to reschedule because the clients are closer to the yard. He also designs routes that keep the trucks in single neighbourhoods. It’s more efficient and jumping on and off the 407 is an expensive proposition, so they use it judiciously.

    7:40

    According to the docket, we were slated to spray two 12-foot Siberian Crab-apples in the client’s back yard. We pulled up and hopped out. Dean walked us to the back of the house saying, “Let’s go find our patients”. I liked that.

    The Process

    Once located, he assessed the trees’ health to ensure the application was appropriate, and then scanned the area. He explained that an arborist had to be very mindful of the surroundings. He ensured nothing was in the path of the hose or the spray, established wind direction, and then (based on tree height and our distance from the truck) estimated the pressure we’d need for the pistol attachment to reach to the treetops.

    We returned to the truck and Dean opened the side to put on his PPE. At the same time, he gave me a short safety lecture. Basically, if I saw anything leaking (on or under the truck) I was to turn off the engine immediately and we wouldn’t go anywhere until we figured out and remedied the issue. Also, should something happen to Dean, I was to call 911. Rest assured, there were no such issues that day.

    He ensured the pressure regulator was completely backed off, opened the intake and return valves on the fungicide tank, attached the pistol to the hose and started up the motor. Then he adjusted the regulator to get us to 150 psi. It was obvious he’d performed this dance many times and as he went through the motions, he noted that it was important to get comfortable with the equipment but to always be respectful of it. Then he partially-closed the side panel to reduce the motor noise and started dragging out enough hose to reach his patients.

    Standing upwind some distance away, I watched Dean work that first tree. He started with a few, short “test shots” into the ground to get the product to the pistol, and to adjust the width of the spray cone. Then a couple more test shots to the top of the tree to gauge the wind and the pressure. I watched him adjust the nozzle to a tighter stream and start circling the tree, spraying in short bursts until he was satisfied he’d achieved the coverage he was looking for.

    Then he detached and drained the pistol before starting back to the truck. I asked what kind of coverage he was looking for and he said the standard was 90% of the canopy covered by at least 90%. That was startling to me given that our unofficial goal for most dilute applications in perennial tender fruit, pome, cane and berry is 100% of the canopy covered, but to a minimum threshold of ~15%. It’s likely due to the different chemistries (I noted earlier that urban applications tend towards biorational products). And, practically speaking, airblast sprayer operators cannot slowly circle a tree, aiming at trouble spots with an endless volume of water. Despite these differences, both methodologies seem to produce acceptable results.

    The Label Dilemma

    I’ve always been sympathetic of sprayer operators working in three-dimensional crops. Interpreting a North American label’s frustrating lack of guidance when it comes to water volumes for non-arable crops places a lot on the operator’s shoulders. I’ve discussed this disconnect (and proposed solutions) in several other articles. I’ve even co-written a book about it. The problem was particularly acute, here.

    Ideally, one would evaluate the target tree’s planted area (which may or may not include an associated portion of alley) and work out the amount of formulated product required for that area. Then, that product must be dissolved or suspended in carrier (typically water) and that gives us the spray mix. Finally, working from the rate the sprayer emits, the operator would determine how much time would be needed to cover the target tree without over- or under-dosing. A good example of the process is found here.

    But… how much water is the right amount? How do we reconcile having to achieve such a high degree of coverage? Does that mean using a more dilute spray mix depending on the canopy, or the chemistry, or the method of application? And what happens when the target canopy size can be variable by an order of magnitude, such as going from a small, sparse tree to a huge, full tree? Would the operator have to change concentrations for every job in order to have the right combination of water volume and chemistry to propel and deposit the product uniformly?

    There’s no easy answer. Yet I watched Dean deal with this problem at every job, working to keep as much spray on target and use only as much spray mix as required to meet his coverage threshold.

    Administration and Cleanup

    Back at the truck Dean shut off the pump and reeled in the hose through a hand-held rag to ensure the hose came back cleaned of anything it may have been dragged through. Overall, it took six minutes to complete the spray job, but then the clients came out to speak to Dean and that conversation lasted another 10. Client interaction / education is a big part of this job.

    By 8:10 Dean had posted a Notice of Service sign in the yard (which must stay there for 48 hours) and punched in the next address on the GPS. As we headed off, he said a big improvement in recent years is the ability to email a Notice of Service and send an invoice right from the client’s driveway, immediately following the service. What traditionally was a 1-2 week wait for payment is now less than a day. If requested, Dean could also write them out manually and leave them at the client’s door.

    8:25

    The next client had five weeping crab apples. These were low trees easily accessed by the roadside truck. Wind was light so low pressure was required. Dean noted that he takes the pressure off the pump between stops to relax the drive belt. He double checked that the pistol was empty and said the reason he drains it after each job was to prevent any possibility of puddles in the truck, on the road or in the client’s driveway. “Customers should never see puddles. It’s better for the environment and it’s professionalism.”

    There’s a lot of wash, rinse, repeat from here on, so I’ll only note anything unique to each spray job. In this case, I watched more closely to understand how Dean aimed. A stream of liquid can traverse a great distance without being deflected by wind, but it’s not the cloud of droplets we generally associate with spraying. I realized Dean was shattering that stream of liquid on the larger branches to create the droplets. That’s also why he occasional pulsed the spray by fluttering the trigger; Sometimes the distance warranted a longer throw (long stream shattering of a branch) and sometimes a series of short pulses (shorter throw and the spray broke up on its own). I watched him as he circled each tree, changing his vantage as required. It wasn’t as easy as he made it look, and he was fast.

    9:05

    This was a single, 20-foot high crab apple tree. Dean cranked it up to 225 psi and started with the pistol. Given the height, the wind was more of an issue, so he waited for lulls, using short pulses over short distances and holding the stream for longer distances. He widened the nozzle only when the wind was light and the target was particularly close, but eventually switched to the long gun to reach the treetop.

    10:10

    This time we were spraying a Magnolia tree. Dean inspected the flowers closely. This tree might bloom for 5-8 days and if the flowers are too open, the oil we would use in the treatment might damage them in high UV. Plus, the mechanical damage from the spray might knock them off. But the flowers were still closed enough for the preventative to be applied.

    You may have noticed that in this case we weren’t using the fungicide, but instead we’d protect the tree from scale using an oil. So how (I wondered) do we empty the pump and 300 feet of hose of fungicide and exchange it for horticultural oil? Thanks to there being no physical or chemical incompatibility with these two products, it turned not to be the “big deal” it would be for most other spray operations.

    Dean opened the draw valve for the oil and kept the return valve open on the fungicide tank. Then he started the pump and hopped up on the truck to spray the fungicide right back into the fungicide tank. When he saw the spray turn opaque, he knew he had primed the oil and stopped spraying. Then he shut off the return on the fungicide tank and opened the return on the horticultural oil tank. The swap took almost no time at all and the subsequent treatment was a breeze.

    10:52

    Stop five was in Snowball Corners in King City and Dean was a little surprised that the work order underestimated the job. We expected a couple crab apples but instead found 20 trees far into a large backyard. Dean took some time with this new client to explain the process, then we fed all 300’ of hose out to reach the trees. We hoped there was enough in the tanks to finish the day!

    Winds were high, but there was nothing around and Dean used short bursts and a tight stream shattered on the trees themselves to reduce the number of driftable fines that would be produced by a wide spray. Slowly, picking his moments, he worked in the up-to-downwind direction so any overspray hit the next target.

    11:37

    One small Crabapple.

    12:00

    Nine ornamental apples.

    Interfacing with the Public

    I used to think that operations like vineyards and orchards, which often suffer the dreaded urban-rural interface, had the hardest time explaining crop protection to the public. And that’s not just agritourism operations with farmgate sales, either. Throughout the day, however, I elevated arborists to the top of the heap. Case in point:

    Before the trucks left that the yard that morning, one of the operators asked Dean about a job in downtown Toronto for a major business on Bloor Avenue. The client did not want applications performed after 8:00 am because hoses on sidewalks are a tripping hazard. They were also restricted from spraying at night because of city noise bylaws (those pumps can be loud).

    Accessing the plants can be very difficult and working in downtown Toronto can be exceptionally challenging. Dean knew the spot by rote, saying they should “Come from the street, look to 1 o’clock and 15 m from the statue to find the boxwoods. Then pace the distance to ensure the 300 foot hose would reach. If not, transfer the chemistry to bottle spray. If so, bring the operating pressure up to compensate for the distance.”

    Dean explained that the crew-leader of each truck makes the call for the most effective and safest set-up. He went on to relate stories about angry neighbours that responded poorly to seeing staff in PPE, or the grief they would suffer when a flower bed or stone path was marred by the hose. He reiterated throughout the day how much of his job was explaining the spray application process to clients, their neighbours and anyone (read everyone) that might be watching.

    Dean said there would always be a way forward if you gave it some thought. “Work the problem. Don’t let the problem work you.”

    12:33

    One backyard crabapple.

    1:10

    Two crab apples in the backyard. This was the last stop and it was perhaps the most complicated. One nearby tree was vibrating with honeybees. The wind was blowing into the neighbour’s yard and the two tall trees were on the property line. Dean really took his time here, rapidly pulsing the pistol whenever the wind died down and directed away from the pollinators. Some overspray moved to the next yard, but it couldn’t be helped. At least it was minimized. All in all we were pleased at the accuracy.

    Then the clients, who were new, came home and Dean once again spent time with them explaining the process. We got back in the truck after posting the sign and as Dean emailed the Notice of Service and the invoice, the first few drops of rain started to hit our windshield. All that patience and effort on the last stop and the client would likely need a re-application the next day. Dean was unflappable: “You can’t control the weather.”

    Epilogue

    We grabbed a late lunch and Dean drove us back to the yard. I’d learned a lot and really enjoyed Dean’s company. He headed back into the office to see how the day went for the other operators and plan for tomorrow. As for me, it had been a long day and I was loathing the punishing drive ahead of me… so I sprang for the 407 toll highway.

    Take Homes

    Upon reflection, and having written this article over about two weeks, I think I’ll end each article with a few observations. Bear in mind that I do so based on a sample size of one. That means what I did and what I saw may be unique; It should not be taken to represent an industry, a company, or even the typical practices of a single operator given that we only spent one day together.

    • Generally, label direction does not adequately inform sprayer operators working in three-dimensional crops. I have noted this in fruit protection systems and greenhouse systems, but it may be particularly relevant for arborists.
    • The classic urban-rural interface can cause friction between agricultural production and surrounding residential areas. Not only as a function of pesticide drift, but also noise, dust, odour, etc. Arborists work in urban environments, are scrutinized constantly and are quite often misunderstood by well-meaning people. As such, their job is far more than product application – they spend a considerable amount of time educating and answering questions, making them front-line ambassadors for crop protection processes.
    • The concept of threshold spray coverage (or minimal effective dose) continues to be a difficult and elusive thing. Factors such as mode of action, the nature of the target (surface structure and location), environmental conditions, application equipment and spray quality/concentration are already tricky to say the least. Having watched the relatively dilute, saturating, and highly mechanical applications performed by an arborist I continue to reassess what I think of as “good coverage”.
    • We sprayed 42 trees in roughly seven hours. Productivity, refill time, travel time and the economic considerations common to all spraying have different standards in each agricultural space. Efficiency is, obviously, important to any operation, but this experience reinforced just how different each operation can be. An orchardist may grumble about having to drive between blocks using county roads but imagine doing that on the 404! It’s all relative.

    Stay tuned for the next installment.

  • The Drive-Along Diaries: Prologue

    The Drive-Along Diaries: Prologue

    I feel it’s important to occasionally remind myself why I do what I do, and who I’m doing it for. With that, let me tell you a story.

    I was recently asked to give a presentation about spray coverage and drift mitigation to an arborist organization. I agreed but harboured reservations. I’ve given talks of this nature many, many times, but I rarely work with arborists. In preparation I looked back through my files and discovered I’d spoken to them 10 years ago. Coincidently, that was also the last time I’d encountered an arborist.

    So, what value could I possibly offer? My concern was that all I’d leave them with was a few “factoids” and the vague sense that they’d been entertained. But would I leave things better than I found them? What could I say that would move the needle and give them something actionable?

    Fortunately, I was paired with a veteran sprayer operator and together we worked out a presentation / demonstration. It went over very well, and I was relieved that people were engaged and asked insightful questions. Crisis averted.

    I believe the reason it worked was because I asked the operator about the real-world challenges (however unpopular) that he faced. We discussed and agreed upon a few lesser-of-two-evils solutions to share with the group. It was authentic, it was pragmatic, and it was appreciated.

    As a result, I decided to dedicate some time this spring/summer to riding along with a variety of sprayer operators as they perform their jobs. If they’d have me, I’d promise to stay out of their hair, acting only as an observer. I wouldn’t make suggestions and I wouldn’t criticize. I would ask the occasional question and I’d watch to see where policy and reality crossed paths.

    I was hoping for a few educational experiences that would inform my research trajectory and teach me a few tips and tricks to share at winter meetings. Perhaps I’d reinforce my understanding of spray application, or maybe I’d be forced to re-evaluate my position on what is a technical truth and what is a practical truth. At the very least I would get to see how professionals did their jobs, and which best practices got sacrificed when things didn’t go to plan.

    And, while I was at it, I decided to keep a journal to create articles in the vein of “A Day in the Life”. You’re reading the first one right now and I hope you find it as interesting to read about as I did to live it. It’s unlikely you work in all the agricultural spaces I’ll be writing about in this series but keep an open mind. The potential for cross-pollination is enormous; Perhaps your “cousin” sprayer operator has solved a problem you face in your own operation.

    And so, given our recent success, my first victim will be my new arborist-friend. You can read all about it here.

    A quick selfie in suburbia as I’m guided through a day in the life of an arborist.
  • Airblast Sprayers for Small Operations

    Airblast Sprayers for Small Operations

    Did you come here looking for advice on which sprayer is best for your small operation? Are you looking to ditch the backpack mist blower? Do you want to avoid repeatedly mounting and dismounting a 3-pt hitch sprayer from your only tractor? Are you concerned you’ll have to sell an organ to be able to afford one? We hear you, and we’ll try to help. Let’s set the stage with a few facts.

    Airblast sprayers stay in service for a long time; more than twenty five years is not unheard of. The majority of them are the generalist, PTO-driven low profile radial design with capacities ranging 150 to 1,200 gallons. Typical fan diameters are around 30″ and can produce >40,000 m3/h of air, making them a good fit for most pomme, citrus and tender fruit canopies. These sprayers come with a horsepower price tag of perhaps 45 hp or more. Many of these sprayers eventually enter the used sprayer market, making them an affordable option for small acreage specialty operations. But, affordability should not be the sole motivation when choosing a sprayer.

    Ontario, c.1980 and probably still out there spraying somewhere!

    The key to optimizing sprayer performance is to match the air settings to the the canopy you’re trying to spray. You can start reading about the process here. In the case of small and medium-sized canopies like vine, cane and bush crops, the fleet of gently-used sprayers we just described tend to produce too much air. There are options to improve the fit, like driving faster to reduce dwell time, or perhaps the operator can employ the Gear-up Throttle-down method. But, the best plan is to employ a smaller sprayer, which produces a more appropriate air volume, has a smaller profile, delivers better fuel efficiency and won’t break the bank.

    So, where are these sprayers? Unfortunately there aren’t many, and options are especially limited if you don’t own a tractor to power them.

    The budget-conscious grower may be tempted to buy a sprayer that does not have air-assist. We do not recommend this. Air is a critical component for spraying canopies consistently and efficiently. Caveat Emptor!

    We encountered a good solution in June, 2014, when we were invited to Durocher Farm in New Hampshire to see their new airblast sprayer. In years previous, spotted-wing drosophila (SWD) was a significant pest in this two acre, high bush blueberry planting. They claimed that since buying their new sprayer they no longer had any trouble with SWD. That’s quite an endorsement!

    The Carrarospray ATVM (200 L pictured)
    The Carrarospray ATVM (200 L option pictured)

    I’m not sure what I expected, but I was captivated by this miniature orchard sprayer. The toy-like size carried a zero-intimidation factor and I immediately wanted to start using it. Italian-made, Carrarospray’s hobby line is designed to be pulled behind vehicles without PTO. The ATVM is available in capacities from 120-400 L. The one I saw had a 400 L capacity, adjustable air deflectors, a fan speed gear box, and it was powered by a quiet and efficient pull-start Briggs & Stratton four-stroke engine. It even had a trash guard, a kick-stand and a clean water tank for hand washing. That’s a lot of features.

    Thanks to Kitt Plummer (Durocher Farm), Penn State, Univ. New Hampshire and Chazzbo Media for filming these 2014 videos:

    The sprayer was pulled (in this case) by a mower, so the grower not only sprayed, but mowed his alleys at the same time. It fit beautifully between the bushes, so the potential for physical damage to the berries was minimized. The air speed and volume was enough to displace the air in the blueberry canopy and replace it with spray-laden air with minimal blow-through. Combined with an appropriate spray volume and distribution over the boom, we found that the coverage it provided was excellent.

    Coverage from the top-centre of the bush. Card is 2x3 inches.
    Coverage from the top-centre of the bush.

    Since seeing this sprayer, we have had reports that importing it to Canada has proved challenging. But there are alternatives. A few companies here in North America offer economy-sized airblast models that are ATV trailed, or skid-mounted, or attached to a small tractor via a three point hitch. PBM’s Lil Squirt is a simple and versatile option. Available primarily in the western US from California through to Washington.

    PBM’s trailed Lil Squirt (Image from their website)

    Another option is the mounted, PTO-driven mistblower line from Big John Manufacturing in Nebraska.

    BJ 3PT mistblower from Big John Manufacturing (Image from their website)

    Or MM Sprayer‘s ATV sprayers, which come PTO or Engine-driven. The LG400 has a 106 gallon tank and a 20″ fan. I’d like to see deflectors, but you could easily add them. Here’s a 2024 pdf on features.

    Picture of the LG400 engine-driven model from www.mmsprayers.usa

    Or Wisconsin’s Contree Sprayer and Equipment. They carry the “Terminator” line. Skid mounted, one-sided air shear units with capacities from 15 to 100 gallons, this company offers a range of possibilities both PTO and gas-driven. Well worth a look.

    The “Terminator” skid-mounted mist blower from Contree Sprayer and Equipment (Image from their website)

    Then there’s the A1 Mist sprayer series, also out of Nebraska. They carry the Terminator line as well as an interesting two-sided volute option that employs conventional nozzles and allows one pass down an alley rather than two. This is a big productivity booster:

    A1’s two-way volute header. (Image from website)
    A1’s PTO-driven 60 gallon, skid-mounted “Terminator”. (Image from website).

    Then there are larger, PTO-driven, three-point hitch options. In fact, there are many options for this manner of sprayer, but they tend to be out of the price range for small operations, and they do require a tractor. That isn’t a deal-breaker, though, as they can sometimes be found used. Pictured below is British Columbia’s Major 193 (Slimline Manufacturing) and a Brazilian-made option (Jacto) distributed out of Quebec.

    Slimline Manufacturing (aka Turbomist) makes the Major 19P 3-pt hitch tower sprayer (PTO-driven)
    Jacto’s Arbus 200 3-pt hitch airblast sprayer (PTO-driven)

    When considering your options, give serious thought to your work rate, refill time and other factors that go into developing a robust spraying strategy. What’s a spraying strategy? That’s a farm’s overall management and operational plan for achieving safe, effective and efficient spray coverage. You can read more in chapter 8 of Airblast101, which you can download for free, here. And, just to play Devil’s Advocate, go small but not so small that the sprayer is underpowered.

    We staged this video in 2011 (spraying only water, so don’t mind the lack of PPE) to show how a sprayer can be too small for an operation. This 3-pt hitch GB cannot overcome the cross wind and the spray barely reaches the apple trees. Reducing travel speed and increasing pressure won’t cut it, either.

    Of course, other possibilities are emerging for crop protection in small acreage perennial crops. Multirotor drones are capable of delivering air-assisted spray from above the canopy. While it’s still a drift-prone and inconsistent means for broadcast spraying, it might lend itself to perennial row crops. Equipment design is evolving quickly and global research is underway to establish best practices. As regulators and agrichemical companies focus more on this method we may see drones as a cheap alternative to a tractor/airblast sprayer, with no compaction, no mechanical damage to fruit/berries, and no potential for splashing infection throughout an operations.

    DJI’s Agras T30

    Even further into the future, small autonomous sprayers may be viable, too. Very much in their early days there is great potential. One example is the XAG Revospray Ground 2 with it’s 150L capacity or the R150 with it’s 100 L capacity.

    The R150 – Image from https://hse-uav.com/. Modular system and ~32K USD (as of 2023)… if you can find one.

    It’s early days, but there are researchers looking at the spray pattern from these units. The image below may not be a fair indication because the nozzle used may not have produced as wide a swath as possible. Thanks to Dr. M. Reinke for the image.

    A test pass using food grade dye. You can see the waveform created by the two spray heads as they move up and down during travel.

    And recently, small autonomous platforms have become more common. Perhaps there’s an opportunity to place a gas powered sprayer on these platforms, or use them to pull a hitch-style sprayer. One such possibility is created by the Burro, shown below at the Ontario Fruit and Vegetable Convention in 2024.

    The Burro autonomous platform.

    Are you aware of a sprayer that’s not in this article? Let us know! Good luck and make sure you have only slightly more “sprayer” than you need.

  • Mode of Action and Spray Quality

    Mode of Action and Spray Quality

    The decision on which application method is best for herbicides boils down to two main factors: (a) target type and (b) mode of action. In general, it’s easier for sprays to stick to broadleaf plants on account of their comparatively larger leaf size and better wettability compared to grassy plants. There are exceptions, of course – at the cotyledon stage, broadleaf plants can be very small and a finer spray with tighter droplet spacing may be needed. Water sensitive paper is a very useful tool to make that assessment. Imagine if a tiny cotyledon could fit between deposits – that could be a miss!

    Some weeds are also more difficult to wet, and those may also need a finer spray or a better surfactant for proper leaf contact. An easy test is to apply plain water to the leaf with a spray bottle. If the water beads off or the droplets remain perched on top in discrete spheres, the surface is considered hard to wet. Most grassy weeds are hard to wet, while most broadleaf weeds are easy to wet.

    Grassy weeds are an especially difficult target because they have smaller, more vertically oriented leaves, and almost without exception are more difficult to wet than broadleaf species. All these factors call for finer sprays for effective targeting and spray retention.

    Broadleaf weeds usually have more horizontally oriented leaves which also happen to be larger. As a result, they can intercept larger droplets quite efficiently.

    There are about thirty mode of action (MOA) groups among the herbicides with about ten accounting for the majority in Canadian prairie agriculture. It’s probably an over-simplification to categorize them into just two groups – systemic and contact.  But that grouping goes a long way to making an application decision.

    Contact products (MOA Group 5, 6, 10, 14, 22, 27) must form a deposit that provides good coverage. Good coverage is an ambiguous term that basically means that droplets need to be closely spaced and cover a significant proportion of the surface area because their physiological effects occur under the droplet, and don’t spread far from there. One way to generate more droplets is to reduce droplet diameter, another is to add more water. A reasonable combination of both is ideal because simply making droplets smaller creates issues with evaporation and drift.

    Systemic products (MOA Group 1, 2, 4, 9) will translocate within the plant to their site of action after uptake. As a result, coverage is less important as long as sufficient dose is presented to the plant. In practice, this means coarser sprays and/or less water may be acceptable.

    When two factors are combined, either in a tank mix or a weed spectrum, the more limiting factor rules. Application of a tank mix or product that is active on both broadleaf and grass plants will be governed by the limitation placed on grass targets. A tank mix comprised of both systemic and contact products is governed by the limitations placed on contact products.

    A factor we should also consider is soil activity and the presence of residue. Studies have shown that soil-active products are relatively insensitive to droplet size. But if they have to travel through a layer of trash to get to the soil surface, more application volume is the best tool.

    Below are some recommended spray qualities and water volumes for use in Canada. The spray qualities listed in the table can be matched to a specific nozzle by referring to nozzle manufacturer catalogues, websites, or apps. Note that Wilger also offers traditional VMD measurements on their site, allowing users to be a bit more specific if necessary.

    Click here to download PDF

  • Drone Sprayers – Are we Ready?

    Drone Sprayers – Are we Ready?

    One of the fastest moving new agricultural technologies is spray drones. Hardly a month goes by without some sort of new capability, some new features. It’s truly an exciting space to watch.

    As with all things, there are good news and bad news to share. First the good news.

    Drone capacity is on the rise. The early drones shipped with hoppers of 8 to 10 litres. Part of the reason was to keep weight below 25 kg. Below this weight, pilot licensing requirements and flight restrictions are easier. Anyone with a Basic RPAS license (RPAS is the official term for drones, Remotely Piloted Aircraft Systems) can operate drones up to 25 kg. Above this weight, one requires an Advanced license, which is much more difficult to obtain. Current drones like the DJI T40 have a hopper capacity of 40 L, allowing more area to be covered per flight.

    The new DJI T40 holds 40 L of liquid and has a claimed swath width of 36 feet (Source: DJI)

    Swath widths are increasing with drone size. The limiting factor for electric drones is still battery power. Flight times of 15 to 20 minutes are possible, depending on the ferrying distance. As a result, larger drones don’t necessarily fly longer, but they spray wider, up to a claimed 30 feet for the DJI T30, and 36 feet for the T40.

    Atomizers are improving. The trusty flat fan nozzle certainly works on a drone, but its proper operation depends on spray pressure. And spray pressure is not currently reported by drones. Instead, their application software relies on flow rate, and pressure is adjusted in the background in response to changes in travel speed, swath width, or nozzle size. Although drone flow meters are remarkably accurate, the operator could inadvertently operate the drone at a pressure that produces the wrong spray quality for the conditions.

    Enter the rotary atomizer. Long a darling of the thinking applicator, these atomizers use centrifugal energy to create a spray with a tighter span, meaning fewer fine and fewer large droplets. Spray quality still depends on pressure-generated flow rate, but droplet size can additionally be altered with rotation speed. This means that if a faster travel speed increases the spray pressure, the effect on spray quality can be counteracted with a changed rotational speed to keep everything more uniform.

    Rotary atomizers, like this one from XAG generate more uniform droplet sizes and can alter droplet size without changing spray pressure.

    Hybrid systems are entering the market. Rotary wings allow for precise positioning of aircraft and they provide downwash that helps spread the spray pattern out. Downwash also improves canopy penetration and could reduce drift, like air-assist, if used properly. But rotary wings use a lot of energy, limiting battery life. When flown at the wrong height or speed, deposit patterns, drift, and swath width will change. That has to be managed and requires experience.

    In comparison, hybrid drones have fixed wings for flight and rotary wings for take-off and landing. The rotors just rotate into the position needed at the time. Fixed wing drones will fly faster, possibly improving capacity and also reducing the effect of the downwash. These systems are new, and much needs to be learned before we understand their various characteristics. But they offer a nice avenue into more productivity.

    Hybrid drones like this one from Advanced Robotics can cover more ground with less turbulence than a rotary wing drone.

    Drones are multi-purpose. Virtually all drones have interchangeable wet and dry hoppers so they can be used to apply dry nutrients or seed as needed. That makes them quite versatile. But the newest spray drones have scouting-quality cameras on board and can be asked to take high resolution images while they’re spraying. At the end of the mission, a very detailed picture of the crop emerges, with much higher resolution than the higher-elevation scouts produce. Other sensors on the drones can be used for variable rate application of nutrients, or even for spot spraying weed patches.

    Scouting camera takes pictures while conducting a spray mission (Source: DJI)

    Now for the bad news. It’s still not legal to apply mainstream pesticides using drones in Canada, and it may stay that way for a while yet.

    Pesticide application by drones remains illegal in Canada. The main reason is that the Pest Management Regulatory Agency (PMRA) has declared drones to be unique application method, separate from ground sprays and aerial sprays from piloted aircraft. This has triggered the need for risk assessment data for spray drift, efficacy, bystander exposure, crop residue. It’s a fair decision – drones produce finer sprays than any other existing system, they potentially use lower water volumes by necessity, and they create a less predictable deposit due to rotor downwash. The majority of current pesticide formulations are designed for 5 to 10 gpa, this creates a certain concentration of surfactants and products that interact with plant surfaces or that change the potency of drift. Altering this by a factor of 5 can have undesirable outcomes. Yes, aircraft also use lower volumes, but more in the area of 2 to 5 gpa. Drones could cut that in half again, and that warrants study.

    Registrants haven’t rushed to study drones. Most major manufacturers of pesticides have a small drone program to get their feet wet, and most have applied for Research Authorization (RA) from the PMRA to study them. But the decision to register a drone use for a pesticide has much to consider. Is it worth it to generate the required dataset for the regulators? Will drones amount to a lucrative new market for product? Do we have the resources and expertise to service this new market? The answers to such questions are clearly complex and much remains unknown. The registrants’ caution is understandable.

    There may be a small portfolio of available products. Anyone thinking that a fleet of inexpensive, nimble drones will replace their ground sprayer is banking on the registration of the products they need in their operatioin by the registrants. The most likely products to be registered are fungicides, for which drones would offer several advantages in canopy penetration and spraying in tight time windows due to, say, wet weather.

    Another obvious use is in industrial vegetation management where rough terrain or remote locations make it difficult to use wheeled sprayers. Or vector control with larvicides, which, incidentally, comprise the first pesticide registrations for drones in Canada (two microbial mosquito larvicides were approved for drone use in October 2022).

    But it seems unlikely in the short term that a producer would have their pick of products to apply by drone anytime soon. And this means that a drone would remain a supplemental tool on the farm, not the main workhorse.

    Regulatory hurdles are substantial. Not only is a pilot required to be licensed to use drones, a pesticide application also requires a Specialized Flight Operations Certificate (SFOC). In general, SFOCs are required if:

    • you are a foreign operator (i.e., not a Canadian citizen or permanent resident);
    • you want to fly at a special aviation event or an advertised event;
    • you want to fly closer to a military airport;
    • you want to fly your drone beyond visual line-of-sight;
    • your drone weighs over 25 kg;
    • you want to fly your drone at higher altitudes;
    • you want to fly your drone carrying dangerous or hazardous payloads (e.g. chemicals);
    • you want to fly more than five drones at the same time.

    SFOC applications are fairly easy to fill out. Aside from identifying the drone and the pilot, the application needs the purpose of the mission, the location of the mission, and the time period of the mission. The problem is that it may take up to 30 days to hear back for simple missions, 60 days for complex mission. And if the SFOC is not granted, you can’t fly. You can’t decide to spray a field at the last minute.

    The news is clearly a mixed bag. We have it all – exciting technology, obvious niche in the marketplace, significant regulations, slow process. In the meantime, spray drones are legal to purchase and relatively inexpensive. And we know they are being purchased. Canada doesn’t have a strong compliance system within the PMRA, so it’s hard to know how much pesticide spraying is being done illegally, or how perpetrators will be treated by the law.

    The reputation of the industry once again rests with hope that good decisions are being made by conscientious individuals.