Category: Mixing

Articles about mixing and pesticide in horizontal boom sprayers

  • Direct Chemical Injection Systems – A Primer

    Direct Chemical Injection Systems – A Primer

    No sprayer operator is more preoccupied with work rates, sprayer cleanout and tank mixes than the custom (aka contract) applicator. Perhaps this is why we’re seeing more direct injection systems on their sprayers in recent years.

    Injection systems employ additional tanks and pumps to introduce undiluted product directly into the carrier just prior to the boom. They are designed to maintain the product concentration in the boom (they are not for variable rate prescription spraying within in a field). This permits the operator to change tank mixes between fields without having to clean out or refill.

    This generic plumbing diagram depicts an injection system that can create custom tank mixes from products held in three separate tanks. The rinse system, number of tanks, pumps and the point of injection (main pump suction or pressure side) are system-specific.

    In the 1980’s, Mid-Tech first offered the TASC peristaltic pump injection system. The bulk of this market was (and still is) right-of-way applications (e.g. railways, highways). Unlike a field application, which covers an area, these sprayers cover a linear distance that makes reloading challenging. When the chemistry is carried onboard, water can be easily accessed along the way.

    Boomless roadside spraying using an injection system (Photo courtesy of TeeJet).

    In the 1990’s, field sprayer operators tried using direct injection and encountered problems:

    • Spray concentrations would fluctuate because product was injected based on travel speed while the carrier rate was a constant.
    • Latency (aka lag) issues were commonplace. Imagine spraying 10 gpa using a boom that holds 15 gallons. A change in speed would prompt a change in injection rate that would not reach the outermost nozzles until half the acre was sprayed.
    • And, changes in temperature affected the accuracy of the injection systems, so rates changed as cold mornings gave way to warm afternoons.

    But the technology has evolved. Today’s injection systems are more consistent and accurate. Here are a few niche usage scenarios to consider:

    Usage scenarios

    1. Anhydrous ammonia applications require nitrogen stabilizers. The stabilizers are intended to treat the soil, not the ammonia. An injection system can introduce nitrogen at a rate that matches a field’s soil type, while the ammonia is applied on a per-area rate.

    2. *Small plot work, such as seed production, consists of many sub-acre plots requiring a range of doses. Injection systems improve work rate by reducing refills or cleanouts between applications.

    3. Where appropriate, border sprays of insecticide can be introduced during herbicide post applications.

    4. Applicators can adjust herbicide mixtures and glyphosate rates between fields depending on weed pressure.

    5. Custom applicators can adjust glyphosate rates when terminating cover crops. For example, alfalfa is a perennial planted for feed before corn. When it gets hardy and begins dormancy late-season, it requires more glyphosate. Oats are used as a cover following winter wheat, and both oats and volunteer wheat require a much lower dose.

    6. Clients of custom application may or may not want foliar fertilizer (e.g. zinc) amendments. This service is only feasible using direct injections systems.

    *This scenario was communicated to the author by a company selling the equipment, but subsequently there has been some question as to how this might work. The amount of time and water required to clear lines between applications would depend on the nature of the chemistry and whether it is a rate or wholesale chemistry change. As such, there are situations that would make this an impractical use of the technology.

    Today’s injection systems

    Mid-Tech/TeeJet

    In early 2000, TeeJet acquired Mid-Tech and offers two injection systems that can control up to six 28 L (7.5 gal.) or 95 L (25 gal.) tanks on a single sprayer. The tanks have an optional agitation feature.

    The MT-500 peristaltic pump (still predominantly for roadway applications) injects into the suction side of the main pump to facilitate mixing. It delivers 6-10 ml/min. (0.2-350 oz/min.) but flow rate can be changed by changing hoses. Peristaltic hoses lose accuracy as they wear with time, but hose is cheaper to replace than seats on a piston pump. It can run in reverse to pull product back from the lines. It works with the TASC controller.

    The MT-600 is a piston-pump with a mixing chamber option that injects the pressure side of the main pump leaving more clean line and increasing response time at the nozzle (i.e. less lag). It must have backflow prevention (typically a seated ball valve). Depending on the rate required, high and low-volume product pumps can be added in pairs to extend the range: 15-1,500 ml/min. (0.5-50 oz/min.), 30-3,000 ml/min. (1-100 gal./min.), 45-4,500 ml/min. (1.5-150 oz/min.) or 60-600 ml/min. (2-200 oz/min.). High and low-volume product pumps can be added in pairs to extend the range. This pump works with TASC controllers and the ISOBUS Legacy 6600 and Aeros 9040.

    Raven

    The Raven Sidekick Pro replaced their original Sidekick in 2011. It is ISOBUS compatible with many sprayers and their controllers (e.g. Deere’s Greenstar 3, Raven RCM). It controls up to five 90 L (24 gal.) or 190 L (50 gal.) tanks with optional agitation that can be removed like totes. Depending on the rate required, low [0.03-1.2 L/min. (1-40 oz/min.)] and high-volume [0.15-6 L/min. (5-200 oz/min.)] positive displacement product pumps can be used alone or in pairs to extend the range. Product is injected into a length of latticed pipe in-line on the pressure side of the main pump to create a mixing action prior to the boom.

    Other entries

    In North America, SurePoint sells the Spartan, which claims to support the direct injection of liquid chemical, fertilizer, biological, or other product into the carrier flow stream. It may be intended for towed implements rather than on a self-propelled sprayer. There are also European entries from Danfoil (theMultidose) and Diimotion (prototype PiiXdi), but information is sparse and the last update we found on either was c.2017.

    In 2025, the UK’s Knight Sprayers won gold at LAMMA 2025 for their Smart-Inject chemical system. Details are light at this point, but it’s described as a third-party retro fit for spot sprayers. Slightly diluted product in held in a second, smaller tank and circulates separately and in parallel with the sprayer’s existing lines. Chemistry is injected on demand (e.g. when a weed is detected) directly into the nozzle body between the shut-off valve and the nozzle cap.

    Pump and tank selection

    Quite often, direct injection users regret limiting their pump capacity and the number of tanks installed. This limits travel speed and encourages risky practices such as mixing multiple products in a single injection tank.

    Direct injection systems should be capable of staying within your target rate and travel speed. You can calculate your pump requirement in oz/min. using the following formula:

    [ Boom width (inches) × Typical ground speed (mph) × Product rate (oz/ac) ] ÷ 5,940

    Summary

    So, if you are considering a direct chemical injection system, give some thought to the following pros and cons.

    Pros

    • Cleanout is faster when the main tank is reserved for water (Although some operators continue to mix in the main tank and use the product tanks to amend the mix).
    • Product tanks are filled from bulk, so there are fewer jugs to handle. That reduces waste and operator exposure during loading.
    • Work rate is improved by altering tank mixes between fields without cleaning and reloading.
    • There is no spray math required during loading and no excess or deficiency at the end of a field.
    • There is no concern about a tank mix sitting for long periods during delays.
    • There is reduced potential for spills due to accident or malfunction.
    • Tracibility is improved; Instead of recording tank mix per acre, record tank mix by field.

    Cons

    • Expense.
    • Rinsing systems, if available, do not clean lines between injection pumps and tanks. Cleaning requires pulling them apart manually.
    • Product tank loading can be slow (up to ½ hr to load 50 US gallons with certain loading assemblies).
    • Some products are harder to clean out than others and can plug the injection pump if left full of chemical.
    • The number and volume of product tanks may not hold a day’s worth of chemicals.
    • Viscous or clay-based products prone to settling or separation (e.g. PrimExtra on corn or Boundry on beans) should not be used.

    Thanks to Rob Warwick and Markus Redmond (John Deere), Dennis Frey and Jordan Diefenbacher (Clean Field Services), Brian Satorius and Andy Graber (TeeJet Technologies), Nick Michael and Gary Esselink (Raven Applied Technology), Jan Langenakens (AAMS) and Mark Ledebuhr (Application Insight LLC) for informing this article.

  • The Label Summary Sheet Proposal

    The Label Summary Sheet Proposal

    We’ve identified and discussed shortcomings in the content and design of today’s pesticide labels in an earlier article. From the perspective of the spray applicator, the information needed most often can be difficult to locate, anachronistic, contradictory, subjective or even missing from the label altogether. To truly encourage an applicator to read and follow the label we need a consistent, concise and clear format that summarizes critical content.

    To that end, we have worked with growers, university/government extension and industry to develop a prototype we’re calling the “Label Summary Sheet”, or LSS for short. We presented the concept in a series of public presentations in western Canada as part of the RealAgriculture TechTour Live event in 2018. You can watch a recording of part of that event at the end of this article.

    The LSS does not replace or interpret the current label, which is a legal document. It is a summary intended to accompany it. At this stage the LSS is simply a proposal. These documents are not intended for use right now; we hope they will grow and change for the better as they stimulate discussion.

    Consider this metaphor: You have just purchased a laptop. When you unbox it, you get an in-depth instruction guide that covers everything from operation to trouble shooting and includes all the legal riders. It’s a daunting technical document that you likely won’t read unless something goes wrong. Knowing that, manufacturers include a graphic and accessible quick start-up guide that summarizes the most common and critical issues. It doesn’t replace the instruction manual, it just augments it. If you can’t find what you need in the quick start-up guide, you are referred to the more fulsome description in the instruction manual. Think of the pesticide label as the instruction manual and the LSS as the quick start-up guide.

    Some agrichemcial companies recognize this need and have developed short documents to summarize key aspects of the label, but they are inconsistent and brand-specific marketing documents that do not always contain the information we are proposing. Here, for example, is the technology sheet for Integrity herbicide.

    We tested the versatility of our LSS format by summarizing four diverse pesticide labels. Our selections are not intended to imply that these labels are particularly deficient. Only that they are commonly used, somewhat complicated and represent the spectrum of pesticide categories and application methods.

    Download and look at the variety of labels we have summarized as examples. They are available here:

    • Pristine (LSS: 3 pages. Pesticide Label: 25 pages)
    • Dual II Magnum (LSS: 3 pages. Pesticide Label: 38 pages)
    • Liberty 150 (LSS: 2 pages. Pesticide Label 20 pages)
    • Traxos (LSS: 2 pages. Pesticide Label: 12 pages)

    Note that each LSS features the same section headings and a relatively consistent layout, no matter the manufacturer. Generic icons are used to illustrate content and make it easier for users to navigate without language barriers. The LSS are black and white to facilitate reproduction and refer back to their respective pesticide labels (i.e. the online PDF, not the booklets that come with the pesticides).

    LSS Sections

    Here is the Pristine LSS broken down by section to highlight the key features.

    1. Banner Section

    The banner is at the top of every LSS. It gives the commercial product name and the date to ensure the LSS reflects the current pesticide label. Four icons represent the most common application technologies: Horizontal boom sprayer, airblast, aerial and handheld. If an application method is prohibited, a banned symbol appears (such as aerial in this case). Note we have left room for RPAAS (UAV’s) anticipating the day we have products registered for that technology. The table notes the type of pesticide (e.g. fungicide, insecticide, adjuvant, etc.). The mode of action and active ingredient(s) are noted, as well as the formulation and the Pest Control Product number.

    2. Resistance Management / Planting Restrictions

    Intended to provide key information on managing pesticide resistance, this section reflects label content about carry over and the rotation of active ingredients. Further, to aid in application decisions, it reflects any restrictions around maximum number of applications, sequential applications or plant back issues following use.

    3. Environmental Conditions


    Any restrictions regarding weather conditions during or after application are noted here. This includes set-backs or buffer zones that reflect method of application and the nature of the adjacent or downwind area in question.

    4. Sprayer Settings

    This section includes the six most commonly asked questions an applicator has when calibrating or adjusting their sprayer prior to use. It is organized by target crop and method of application. When the label provides a high level of detail, the user is referred to the correct page. Note the use of graphics to quickly direct the reader to the information they need. Any additional qualifications found in the label relating to sprayer settings are indicated in the notes beneath the table.

    5. Handling Safety (PPE)

    The concept for this simple and graphic table originated in France, and was communicated to us by Dr. Carol Black of Washington State University. This unambiguous  format encourages the use of PPE while ensuring the handler uses the appropriate level of protection for each activity.

    6. Mixing


    As operators tank mix more products to curtail resistance, improve efficacy or improve productivity, there is a greater chance of chemical or physical incompatibility. This section summarizes any restrictions noted in the label. Learn more by downloading Purdue Universities’ publication “Avoid Tank Mixing Errors“.

    7. Rates and Restricted Entry Intervals

    This table can be quite complicated depending on the pesticide label. It summarizes the rates, volumes and restricted entry intervals by crop. It reflects the broadest range of product rates listed in the label. Restricted entry duration is affected by the post application activity, and this is captured in the REI column. If more detail is required, the user is referred to the appropriate page(s) of the label. Any additional qualifications found in the label relating to rates, volumes or REI are indicated in the notes beneath the table.

    8. Equipment Cleanout

    Finally, equipment cleanout is summarized (where possible) in a sequence of steps. When the pesticide label is silent on the cleanout procedure, the user is provided with the triple rinse protocol, which is generally held to be the industry best-practice.

    Adoption

    To date, this proposal has been made to Croplife Canada, the American Society of Agricultural and Biological Engineers (ASABE), an International Organization for Standardization (ISO) mirror committee (Equipment for crop protection) and more than 1,400 growers and stakeholders across Canada.

    Our suggestion for adoption of the LSS (in its current form or something similar)  is that regulatory agencies commission a working group comprised of representatives from grower groups, industry and government to oversee the process. The working group would support registrants as they populate (or update) the LSS template when a new product is submitted for registration, or as part of the natural review cycle.

    Should the registrant encounter duplicate, missing or contradictory information while completing the LSS, it should be considered an opportunity to remedy the problem on the pesticide label. This will clarify the safest and most effective use of the pesticide for the applicator, who is currently forced to selectively ignore or interpret such errors. To our minds, this was the intent of the original labelling system, and the inclusion of the LSS is a simple and effective way to achieve that goal.

    The Confusicol Sketch

    In 2018 we participated in Real Agriculture’s TechTour Live event that toured four major cities in Western Canada in four days. We presented the “Confusicol sketch” as a light-hearted way to open a discussion with the audience on the strengths and weaknesses of Canadian pesticide labels and how the Label Summary Sheet might be a viable supplement. Here’s one of the live takes, warts and all. Turns out live sketch comedy is tricky…

  • Loading a Sprayer? Add Time and Patience!

    Loading a Sprayer? Add Time and Patience!

    What’s the most underused active ingredient when creating a proper tank mixture in a sprayer?

    Patience.

    Spray season is never long enough. The days which are most conducive to spraying are hard to come by. Therefore, the ingredient we need the most when spraying as well as tankmixing is patience. Without it, we are setting ourselves up for failure.

    Successful bakers will tell you that patience mattered when perfecting their most decadent creations. By taking their time, adding ingredients slowly and mixing them carefully, those professionals create stunning masterpieces.

    We can achieve a masterpiece as well, if we remember to slow down and apply the same principles.

     1. Take your time

    • Take 7-10 minutes between product additions to a spray mixture (especially dry formulations). Have a mini-vacation after each addition! This time allows each product to dissolve into solution and you can complete your spray records!
    • Extra time allows pesticides to be fully integrated into the spray solution before another product is added, which could impede either formulation from mixing successfully.
    • Each ingredient must be uniformly mixed before adding the next component. E.g. A soluble powder must be completely dissolved before adding the next item.

    2. Add ingredients slowly

    • Add products, one at a time, in the mix cone or inductor. If you’re adding product directly via shuttles and dedicated lines, the same principle applies.
    • Rinse mix cone or inductor and lines with clean water between product additions.
    Tank, cone or inductor, mix products one at a time and rinse between additions.
    Anything resembling cottage cheese in your spray mixture is not a spray masterpiece.
    • Never “stack” ingredients on top of each other in the mix cone or inductor. Much like oil and water don’t mix, chem-on-chem doesn’t mix either. Active ingredients need water in order transition into solution. It’s vital to not pile products into a mix cone or inductor where they can form cottage cheese instead of a liquid solution.
    • In my neighborhood, 3″ fill lines are not uncommon. They are a source of time savings when filling but they also bring additional cautions. Be aware of the problems over agitation can bring to what might have been a successful tankmix.

    3. Mix carefully

    • Start with sprayer tank 1/3-1/2 full to allow enough water to create a great solution.
    • Pre-slurry dry flowables in warm water whenever possible. Yes, it takes additional time and effort but it can prevent having to wash out individual nozzles and strainers later. Or worse, there’s the possibility that the tiny grains of an active ingredient that did not blend into the solution may cause injury to a off target crop.
    • Mix ingredients in the right order! Typically, crop protection products have a mixing order specified on their labels. Read the label and be familiar with the correct formulations you are currently spraying.
    • Adjuvants are added in the same sequence as pesticides, e.g., ammonium sulfate is a soluble powder, oil adjuvants are emulsifiable concentrates; and most surfactants are solutions.
    • Within each group, it is common practice to add the pesticide before the adjuvant, e.g., a soluble-powder pesticide before ammonium sulfate.

    Final thoughts

    Taking the extra 30 minutes now to load the sprayer carefully will save you the potential of 4 hours of having to clean out an entire tank later!

  • Sprayer Loading and the Jar Test

    Sprayer Loading and the Jar Test

    This article was co-written with Mike Cowbrough, OMAFRA Weed Management Specialist – Field Crops

    The time and attention spent during sprayer loading is a worthy investment. It ensures that the products in the tank perform as intended and reduces the chance of physical incompatibilities.

    The label

    Pesticide labels are always the first point of reference. Labelled mixing instructions should be obeyed even if they contradict conventional practices (see Mixing order, below). Consult this article on tank mix compatibility for more information on how to quickly and easily consult labels for each of your tank mix partners.

    The carrier

    Typically, the carrier is water. Water plays a very important role in tank mixing that is often underappreciated. Take some time to read Les Henry’s 2016 Grainnews article called “The Coles Notes of Water Chemistry“. You can also read about pH and water hardness. It should be noted that pH and the resultant hydrolysis that can affect product half-life is typically an insecticide issue (not fungicide or herbicide). The famous example is Captan, which has a half-life of 32 hours at pH 5, but only 10 minutes at pH 8. Michigan State did a great summary (in 2008 and on US product formulations) which you can find here.

    Finally, learn how to read a water quality report, here.

    Carrier volume

    Products dissolve better in higher volumes. The sprayer tank (vat, inductor, etc.) should be at least ½ full or water before adding the first product. In the case of a fertilizer carrier, it may look like water, but it contains high levels of salts that tie up free water and reduce solubility. For fertilizers, a higher initial volume of ¾ full is required.

    Note the undissolved residue collected on these swatches of red material. Products dissolve faster and better in higher carrier volumes.

    The incomplete dissolution of products can leave hard-to-clean residues, plug fluid lines, and result in a non-uniform application that reduces efficacy. The risk of incompatibility is greater with low carrier volumes and high product rates (especially dry formulations). This is a common problem in regions that use low water volumes to apply multiple tank mix partners.

    Carrier and product temperature

    Both carrier and product temperature affect mixing. Imagine mixing sugar in hot tea versus iced tea – more sugar dissolves more quickly in hot liquid. Here are three common temperature-related issues:

    • Dry formulations and liquid flowables take more time to disperse (consider using a pre-mixed slurry).
    • Emulsified concentrates and oil might form gels rather than milky blooms.
    • Water soluble packages might not dissolve completely and could plug filters and nozzles – or clog the pump intake.
    Note the undissolved residue collected on these swatches of red material. Products dissolve faster and better when carrier and products are warmer.

    Note: Water and fertilizer are very different carriers. Beware of carrier-specific incompatibilities

    Agitation

    Agitation should be on-going during mixing and spraying. When agitation is too low, products may not disperse or suspend and can settle out. In the case of leaving a sprayer overnight without agitation, settled product may or may not resuspend. See this article.

    When agitation is too aggressive (e.g. full agitation when tank is less than half full) product can foam, causing overflows or breaking pump suction during spraying. Over agitation can also cause dispersed products (e.g. emulsifiable concentrates) to separate and cause clumping that looks like curds.

    Note: When agitating, the surface of the carrier should be closer to a simmer than a rolling boil.

    Pace

    Products may require more than five minutes between additions. This is especially important when carrier or product is cold, or when adding dry products. When products are added too quickly, they will not entirely disperse or suspend, which could result in a physical incompatibility with subsequent additions. Learn more about the importance of time and patience during loading.

    While efficient sprayer loading is an excellent opportunity to improve your work rate, complicated tank mixes still require time between additions. To save some time, sprayer operators pre-hydrate dry products in a smaller tank or use an extra tank to pre-mix whole loads and simply transfer them over.

    Note: Even when dry products appear to be dissolved, they may not be. Be patient

    Product formulation

    Product formulation is a complicated science. In the 1950’s a formulation might have three active ingredients and an inert filler. See the historic formulation index card shared by Dr. M Doug Baumann (formally with Syngenta, Honeywood). Today, a product can include ~40 ingredients with formulation testing lasting two to four years! The more products you add to the tank, the higher the risk of antagonism.

    Note: If you experience physical incompatibility during loading, don’t blame the last product you put in the tank!

    Mixing order

    The order in which you add tank mix partners is critical. There are several acronyms around to help you decide on your mixing order. Here are the top three:

    • W.A.L.E.S. (Wettable powders, Agitate, Liquid flowables, Emulsifiable concentrates, Surfactants).
    • BASF’s W.A.M.L.E.G.S. (Wettable powders, Agitate, Microencapsulated suspensions Liquid flowables, Emulsifiable concentrates, high-load Glyphosates, Surfactants)
    • A.P.P.L.E.S. (Agitate, Powders soluble, Powders dry, Liquid flowables and suspensions, Emulsifiable concentrates, Solutions)

    W.A.L.E.S. is not broken. In fact, formulation chemists expect it to work ~95% of time. Generally, soluble liquids are forgiving and can be added early or late. It’s the dry formulations and emulsifiable concentrates that require more care. When there are exceptions to the order, they are clearly indicated on the pesticide label.

    W.A.L.E.S. is, perhaps, a bit simplistic. Products that fall within each “letter” have their own preferred mixing order that isn’t specified by the acronym. What follows is an expanded generic mixing order.

    • Water-Soluble Bags (WSB) – Allow them to fully dissolve and disperse.
    • Wettable Powders (WP)
    • Water Dispersible Granules (WDG, WG, SG)
    • Agitation to allow dry products to mix and disperse.
    • Liquid Flowables (F, FL): Including, in order, Suspension Concentrates (SC), Suspo-emulsions (SE), Capsule Suspensions (CS/ZC), Dispersible Concentrates (DC), Emulsions in water (EW).
    • In order: Emulsifiable Concentrates (EC): Microemulsifiable Concentrates (MEC) and Oil Dispersions (OD).
    • In order: Solutions (SN), Soluble Liquids (SL), Liquid Fertilizers and Micronurients (when not already premixed with fertilizer).
    • NOTE: Regarding adjuvants, always follow the label. If the label is silent, most water conditioning utility modifiers (e.g. compatibility agents, anti-foamers) should be added before pesticides. However, drift retardant utility modifiers are added dead last. Activator adjuvants like Non-Ionic Surfactants (NIS) and Crop Oil Concentrates (COC) tend to be added after pesticides, but are sometimes added based on their formulation, falling into order just like pesticides. Again, read the label.

    An example

    Micronutrients like sulfur (e.g. ATS) added to nitrogen-based formulations (e.g. UAN) can cause physical incompatibilities. This became a problem during “weed-and-feed” applications in Ontario corn, and thanks to the efforts of the pesticide manufacturer, we worked out a solution.

    What follows is not only a good example of why mixing order is critical, but why growers should get into the habit of performing jar tests. Learn more about a real-world ATS example here.

    Left: ATS and UAN premixed, followed by Primextra created curds.
    Centre: UAN, followed by low-load ATS followed by Primextra worked.
    Right: UAN followed by Primextra followed by high-load ATS worked.

    Small-plot mixing order

    Mixing errors are just as likely in small plot work as in commercial sprayers. Watch this short video case study describing mixing order for Elevore and glyphosate.

    The jar test

    Performing a jar test is like filling a sprayer in miniature. Follow all the same rules as filling your sprayer. Always wear personal protective equipment when performing a jar test. Do so in a safe and ventilated area, away from sources of ignition.

    1. Read all product labels. Know the product formulation (which affects mixing method and order). Look for information about the influence of carrier pH, hardness and any requirement for adjuvants. Defer to label instructions should they differ from these mixing steps.
    2. Shake any liquid products. This ensures the active ingredient and inert ingredients are thoroughly mixed.
    3. If using water as a carrier, add 250 ml to a 1 litre glass jar. For oil or fertilizer, add 375 ml.
    4. Agitate (stir) between additions. In a sprayer, agitation should continue throughout the mixing process.
    5. Add products in order (see Mixing order, above). Scale back the weights/volumes used to match the concentration intended for an actual sprayer tank (e.g. 1 kg product in a 1,000 litre sprayer tank is 0.5 g product in a 500 ml jar test). In a sprayer, you would flush an inductor with water between additions.
    6. Wait and check. Dry products and water-soluble packets must fully disperse and/or dissolve before adding the next product. Several factors affect the duration, but 3-5 minutes is typical. If testing water-soluble packets, include a ~1cm2 cutting of the PVA packaging.
    7. Top up the carrier to 500 ml.
    8. Measure pH using a digital meter (litmus papers may not be readable). This is best done after all products are added to account for their impact on pH and buffering capacity. If required, pH adjusters can be added at the end of mixing to ensure the solution is in the range required by the label.
    9. Let the solution stand in a ventilated area for 15 minutes and observe the results. If the mixture is giving off heat, these ingredients are not compatible. If gel or scum forms or solids settle to the bottom (except for the wettable powders) then the mixture is likely not compatible.

    Note: jar test will only reveal physical incompatibility between products – it will not reveal any other form of antagonism.

    Compatibility kits

    When performing a jar test you must maintain the same product-to-carrier ratio as in a full-sized sprayer tank. This math is made easier with commercial compatibility kits such as the one from Precision Laboratories (below).

    Compatibility Test Kit: Five pipettes, three bottles, gloves, instructions. ~$10.00. (Photo: Precision Laboratories)

    Such kits contain a few plastic “jars” and disposable micropipettes. By following the instructions included with the kit, you can easily reduce large labelled volumes (e.g. 1 kg of product in 1,000 litres) of multiple products to small volumes at the same ratio. In this case we assume the final volume would have been 1,000 L, and so we reduce all the quantities accordingly to get 500 ml. The following mixing order is provided as an example.

    OrderIngredientQuantity for 500 ml or 500 g of product labeled for 1,000 L of final spray volume
    1Compatibility agents5 ml (1 teaspoon)
    2Water soluble packets, wettable powders and dry flowables. Include a 1cm2 cutting of PVA packaging.15 g (1 tablespoon)
    3Liquid drift retardants5 ml (1 teaspoon)
    4Liquid concentrates, micro-emulsions and suspension concentrates5 ml (1 teaspoon)
    5Emulsifiable concentrates5 ml (1 teaspoon)
    6Water-soluble concentrates or solutions5 ml (1 teaspoon)
    7Remaining adjuvants and surfactants5 ml (1 teaspoon)

    Records and delayed reactions

    Keep detailed records of what you mixed and how you mixed it. This is important for traceability (e.g. CanadaGAP) and for tracking successes and failures for next year.

    The jar test itself can become a valuable record if it’s labelled and left in the chemical shed. You will see if products separate, precipitate or form residues. This may indicate if you can let a tank mix sit overnight or if it will require special attention during rinsing.

    For example, a grower tank-mixed Enlist with Manzinphos, which seemed to mix and spray with no issues until they were rained out and had to park the sprayer with 100 gallons of tank mix still in the system. The mixture turned to “lard”, plugging up all of the lines, filters, and the pump. They had no choice but to disassemble the sprayer and dig some of the substance out with screwdrivers (see the picture of the filter below). Perhaps if they had run a jar test and left the jar overnight this problem could have been avoided.

    Some physical incompatibilities are not immediately apparent. This occurred overnight while the partially-full sprayer waited out a rain event.

    Closed transfer

    As a brief mention, an expansion of closed transfers systems for loading pesticides is on the horizon in North America. Manufacturers of these systems claim they will make loading more efficient, reduce operator exposure and reduce point-source contamination. Depending on the design, however, the operator may not be able to open pesticide containers to obtain samples for jar testing. This would be a great loss.

    For more information

    Learn more about physical and chemical incompatibility in our article on Tank mix compatibility. Be sure to download a copy of Purdue University’s 2018 “Avoid Tank Mixing Errors”. It is an excellent reference.

  • Do Labels Help us Apply Pesticides Properly?

    Do Labels Help us Apply Pesticides Properly?

    It happened three times this spring.  As is often the case, I was contacted by growers who wanted help with herbicide application.  In most of these calls, the discussion revolves around the proper choice of nozzles for a specific task, perhaps some questions on spray pressure, water volume and travel speed.

    But these three were different.  Instead of being seasoned applicators, all three were new to the business.  And more importantly, they had done their homework by looking at product labels before calling.

    Labels give us important information on product rates, crop and weed staging, mixing order, sprayer cleaning, and personal and environmental protection.  They’re very valuable there.  But they also provide application information, and that’s where the problems begin.

    Perseverance Required

    I have to commend my three clients:  they showed great tenacity by actually finding application information on a pesticide label in the first place.  This document is so mired in legalese protectionist language at the front that it discourages all but the most persistent.

    And often, the application information comes in several parts, interspersed among other information.  Mixing instructions.  A little later, application. Somewhere nearby, buffer zones.  Another paragraph for cleaning.  Rainfastness?  Keep looking.

    It forces the reader to skim through the document, hunting for relevant information.

    But once my clients found application instructions, they obviously questioned if they should believe it, or else they wouldn’t have called.  The application statements on many labels, simply put, are from long ago, and it’s obvious.

    Consider the following two label excerpts, the first from a product initially registered in the mid 1980s and still available, the second from one registered about 30 years later:

    1980s:

    Application should be made using a minimum of 55-110 litres of water per hectare, at a pressure of 275 kPa, or 310 kPa if using check valves, and at a ground speed of 6-8 kph.

    The use of 80° or 110° flat fan nozzles is recommended for optimum spray coverage.

    Do not use flood jet nozzles, controlled droplet application equipment or Sprafoil® equipment.

    Application of the spray at a 45° angle forward and higher water volumes will result in better spray coverage and penetration of the crop canopy.

    Uniform, thorough coverage is important to obtain consistent weed control. Higher water volumes should be used under dense crop and weed canopies to ensure thorough coverage of the target weeds.

    2010s:

    Apply in a spray volume of 46.8 – 93.5 L/ha unless otherwise specified in tankmix partner section of this label – at 207-345 kPa (30-50 PSI) pressure to ensure proper weed coverage.

    Flat fan nozzles of 80° or 110° are recommended for optimum coverage.

    Do not use floodjet or controlled droplet application equipment or Sprafoil® equipment.

    Nozzles may be oriented 45° forward to enhance crop penetration and to give better weed coverage.

    Uniform, thorough coverage is important to obtain consistent weed control. Higher water volumes should be used under dense crop and weed canopies to ensure thorough coverage of the target weeds.

    Thirty years apart, but remarkably similar.

    Crop protection companies spend about 10 yrs. and $250 million to produce a new pesticide and register it for use.  Having made this commitment, it would be most useful to see a small further investment to provide current application information that is relevant to applicators.

    After all, these applicators purchase the active ingredient to provide a return on this multi-million dollar investment, to the tune of about 2 billion dollars per year in Canada alone. They deserve good application information.

    Imagine this scene:

    “Doctor, thank you for this new high tech pharmaceutical engineered to help me with my serious illness.  How should I take it?”

    “Not sure.  Here, read this cough syrup label I found in my drawer.  Should be pretty close.”

    It’s clearly ridiculous

    Let’s dissect these labels to see how they could be improved.

    Flat fan nozzles of 80° or 110° are recommended for optimum coverage…

    Our sample labels refer to what we assume are conventional flat fan nozzles.  While popular in the 80s, these have all but disappeared from sprayers over the course of the past 20 years or so.  We haven’t recommended them since then because they drift too much. They’ve been replaced by low-drift nozzles, either pre-orifice, or air-induction.

    Nozzle fan angles are now generally 110 degrees or more, and frankly, the difference between 80 and 110 degrees is not that important.  What’s important is proper overlap, achievable with a visual assessment followed by boom height and pressure adjustments.  Unfortunately the label is silent on that.

    Application should be made … at a pressure of 275 kPa, or 310 kPa if using check valves…

    A nozzle’s recommended operating pressure depends on the specific nozzle model and on the spray quality (average droplet size) required. With literally many dozens of nozzles now available to each applicator, general pressure suggestions are likely to be wrong, and are more of a liability than a help. And they force label non-compliance when over-ruled by a nozzle manufacturer’s recommendations.

    Speaking of spray quality, growers crave to know at what spray quality a product should be applied for best performance and lowest drift. Some labels refer to spray quality (e.g. “apply with a Coarse spray”), but this is with reference to spray drift and buffer zone distances, not efficacy, and that distinction is not made.  Knowing the right quality for efficacy would help applicators choose the right nozzle and pressure to meet that criteria.

    Higher pressures if using check valves?  Nobody has brass screens with check valves anymore.  Sprayers have had modern diaphragm check valves for a generation, and those don’t produce pressure losses.

    And we all know that six to eight km/h is hardly a common speed these days.

    Do not use floodjet or controlled droplet application equipment or Sprafoil® equipment

    Sprafoil nozzles have not been produced in Canada for about 25 years, in fact their manufacturer is no longer in business.  Controlled droplet atomizers, while becoming more popular again on aircraft, were last seen on ground sprayers in the 1980s. Even then, total installed numbers were probably in the single digits.

    As for FloodJet nozzles, those went out of style for herbicides in the late 70s, and were replaced by the very successful TurboTeeJet nozzles shortly after.

    Nozzles may be oriented 45° forward…

    Nozzles are rarely tilted 45 degrees forward for herbicide application anymore.  Maybe that’s because spray booms aren’t built that way today, or because modern booms on self-propelled sprayers are now about 30” (75 cm) above ground, and we travel at about 15 mph (22 km/h).  So the forward tilting, though shown to be effective for grassy weeds at 5 mph (8 km/h) and 20” (50 cm) boom heights, as researched in the 1970s, isn’t relevant for herbicides with higher booms.

    Uniform, thorough coverage is important to obtain consistent weed control.

    Statements advocating for good coverage are nice, but they aren’t useful.  Everybody knows we want good coverage.  What applicators need to know is how they should measure coverage, and what good coverage actually is.  Can we use water-sensitive paper?  How much of the target should be covered?  How many droplets should be in each square centimetre?  How can we measure that in the field, right now? How does it depend on the crop canopy, on weed stage, and on spray quality? The more information an applicator gets, the higher the chance of success.

    Apply in a spray volume of 46.8 – 93.5 L/ha…

    The only statement that survives our little examination is about water volume. Water volume is important.  But even there we have a problem.  The volume is in L/ha.  This is useful in some parts of Canada, but not in the west, where producers communicate primarily in US gallons per acre.  And in the west, provincial guidelines have generated this odd hybrid of L/acre, which few people use for spray volume.  But 46.8 to 93.5 L/ha?  How is that level of precision justified? (I know that this is a conversion from 5 and 10 US gpa…so why not just say so?)

    A Solution

    The problem with having outdated or impractical information on labels is that it creates disrespect.  Since labels are documents enforceable by federal law, applicators want to comply. At this time, they can’t, and probably shouldn’t, if they want to do the job right.

    A vision for a good label should be one that respects the needs of the applicator.  Such a label:

    • places the information that applicators need at the top;
    • is updated regularly to reflect modern practice and useful advice;
    • helps a new applicator work out how to apply the product with any equipment;
    • identifies a spray quality that offers good coverage and low drift;
    • makes reference to research that supports variations in the application guidelines;
    • is available electronically, readable on a mobile device, i.e., not pdf.

    This label would protect the environment and bystanders, and would foster better pesticide performance.

    This label is easy to generate.

    This label would be read by applicators.

    What’s it going to take?

    Additional:

    This article created a great deal of discussion. We decided that if we were going to point out issues with the current labelling system, we should also propose a way forward. Read about our Label Summary Sheet proposal.