Tag: pesticide

Operator Safety: How to Avoid Pesticide Hazards
A Veteran Applicator’s Questions about Pesticide Handling
Time and again, after years of working with dozens of different chemicals, I would wonder to myself “How dangerous is this chemical?”, “Is glyphosate as safe as they say it is?”, “How do I find out what type of safety gear I need while handling this chemical?”
Beyond the agrichemical dealer, ag. consultants, and university or government ag. extension specialists, a quick internet search reveals many sources of pesticide information. Collectively they identify the active ingredient(s) in formulated products, they detail which pests are best controlled by the pesticide, and they provide instruction for application. But it’s more difficult to find consistent, practical information about safe pesticide handling. Sometimes it’s excessive to the point of being impractical (try finding actual “chemical proof” gloves), and sometimes it’s minimal and vague – it depends where you look. No matter the level of precaution, pesticide safety is time consuming and involves some fussing, but it is the hallmark of responsible pesticide use. Just as we ensure that we are applying “safe rates” when spraying chemicals, we must also ensure we are respecting our own well-being while handling chemicals.
In Canada, the Pesticide Regulatory Directorate (PRD) is charged with protecting human health and safety by monitoring pesticides that are sold in this country. According to the Federal Pest Control Products Act all pesticides sold in Canada must be registered with the PRD. There’s a very nice overview of how that process works here. It is during this registration process that pesticide handling precautions are identified for the label. Further classification may take place under provincial acts.
All pesticides are designed to disrupt, repel, control or kill living organisms, but when it comes to safe handling, insecticides receive the most attention. This is because herbicides and fungicides target biochemical pathways that only exist in plants or fungi. However, most pesticides can be hazardous if they are not handled correctly. The handling precautions that appear on the label are based on five factors.
Five factors that affect handling precautions:
1. Pesticide Family
This factor is the broadest way to categorize potential risk to the handler. Generally, herbicides and fungicides are considered safer than insecticides, but there are notable exceptions. Do not rely solely on the pesticide family when making decisions on pesticide handling.
2. Pesticide Mode of Action
The mode of action gives further detail into how a pesticide should be handled. Modes of action that inhibit biochemical pathways that exist in the target pest, but not in mammals (people, in particular), have lower acute toxicities. Examples include herbicides that inhibit enzymes involved in amino acid synthesis or in photosynthesis – these enzymes do not exist in mammals. However, once again, there are always exceptions. Do not rely solely on mode of action when making decisions on pesticide handling.
3. Pesticide Formulation & Route of Entry
Pesticide formulation affects how a product can potentially be absorbed into the body. Emulsifiable Concentrates (ECs), for example, have higher rates of absorption than solutions or dry products. When it comes to the route of entry, dermal contact is considered safer than inhalation or ingestion. However, not all parts of your skin are created equal, and the point of dermal contact on the body matters a great deal.
4. Pesticide Toxicity
Taken collectively, the first three factors form the overall toxicity of the pesticide. The level of toxicity cannot be predicted – it has to be tested. The LD₅₀ (defined below) values that are reported for a pesticide come from standardized experiments such as animal feeding. Although the chosen species (usually white rats for mammalian endpoints) are known to be similar to humans in their response, there is still the possibility of error. Nevertheless, toxicity forms an important basis for establishing handling precautions.
5. Operator Exposure
People handle toxic substances every day. Household bleach, for example is surprisingly toxic, and yet it can be readily found on kitchen shelves in many homes. The risk of being harmed by a toxic product can only be determined by the likelihood of exposure. While it is possible someone might accidentally consume a hazardous dose of bleach, it’s improbable. Exposure does not just refer to a single exposure to a substance – repeated exposures to small doses of a toxic substance can have a cumulative effect. The goal when handling any pesticide is to minimize exposure, but it becomes even more critical when that pesticide is highly toxic. Together, exposure and toxicity form the basis for risk.
Risk = Hazard x Exposure
Studies have shown that exposure is greatest for handlers of agricultural pesticides during the mixing and loading phase of spraying. During this phase, the risk to the handler may be increased due to:
- physical stress
- the denial of risk
- a negative opinion of personal protective equipment (PPE)
The main method of pesticide exposure is dermal, and many of the surfaces on a piece of equipment are already contaminated.
Health effects of pesticides: Acute and Chronic
Acute: short term
High exposure, resulting in immediate reaction due to a high dosage of pesticide exposure. The severity depends on the toxicity of the molecule and entry into the body (dermal, oral, eyes, etc.). The most common acute reaction is skin irritation, although in certain cases respiratory, digestive, and neurological systems may be affected. Organophosphate (e.g. Lorsban, Malathion) and carbamate (e.g. Sevin, Lannate) insecticides inhibit the cholinesterase enzyme, which is found in humans and affects nerve function. Frequent users of these insecticides undergo regular blood tests to ensure their levels are normal.
Chronic: long term
Chronic affects are more prolonged as they are usually due to lower doses of pesticide exposure over a longer period of time. Although some rare cancers and disruption of the reproductive system have shown to be related to this type of exposure, when the general population and farming population have been compared in studies, the farming population has shown an under-representation in the majority of cancers. In the cases were reproductive malfunctions were observed, a different cause of the malfunction, such as genetic offset, was most often observed in these situations. However, cancer types such as skin cancer and brain cancer were overrepresented in the farming community. A study in France has shown that the onset of neurological disorders in Agriculture communities shows a strong connection between Parkinson’s disease and exposure to pesticides.
Label Information
The majority of information needed to safely handle pesticides is found on the label. Pesticide labels are legal documents, meaning they can be enforced by the federal government. The problem is that most sprayer operators rarely look at the label as they are not very reader friendly and easy to skim through. Most pesticide boxes even have the recommended rate, or acres/case on the side of the box now, so there is even less reason to look at the label.
LD₅₀– the dose of pesticide in mg per kg of the test animals body weight that is lethal to 50 percent of the group of test animals. For example, if the pesticide has an acute oral LD₅₀ value of 1000 mg/kg, and the test animals each weigh 1 kg, then 50 percent of the animals would die if they each ate 1000 mg of pesticide at once. A 100 kg animal would need to ingest 100,000 mg (100 g) of the pesticide for the same effect. LD₅₀ is often expressed by the route of entry – dermal, inhalation, acute oral (ingestion) are the main examples.
Degree of Risk and Hazard Symbols
Two Factors that Determine the Appropriate Level of PPE
1. The Hazard Rating (above) incorporates the minimum protection generally required for a substance with the rating.
2. The Label Recommendations will usually give the additional specific protective clothing and equipment needs for an applicator.
Degree of Exposure
This increases as the length of each pesticide application increases. As the number of pesticide applications increases, the time between exposures decreases. If an operator becomes exposed to spray, dust or fumes the degree of exposure increases. Essentially, more protective wear is needed as the degree of exposure becomes greater.
Knowledge
This encompasses all of the above information. In order for a pesticide applicator to avoid injury or the chances of adverse effects on the body, a pesticide applicator must be knowledgeable about pesticides. It can be overwhelming for an applicator to sort through all of the information on the label or on-line regarding pesticides. So much so, that most often applicators avoid the information altogether. Ongoing training and learning will ensure that they are effective in their work. Many aspects of pest control change continuously, as new studies are conducted on the effects of pesticide exposure.
A Safety Data Sheet (SDS) is available for each pesticides registered, and these are usually linked on manufacturers’ websites. It can be eye-opening what types of toxicity tests are done, and what the results are.
Denial that pesticides can potentially cause harm is also a major flaw in the behaviour of applicators. Maintaining a safe work environment and practicing personal safety will reduce the chances of an applicator experiencing serious injury throughout their farming career.
Unknowns
There is very little certainty in toxicology. For one, most testing is done using acute oral and dermal dosing. Basically, toxicologists expose test animals to the neat active ingredient and watch what happens. There is a lot of missing information – what about formulant like solvents, and surfactants? What about synergies in tank mixes? Some, but not all of these, undergo testing. We also have much less information on chronic (long-term) effects, and can only simulate these in quasi long-range tests. In addition, toxicological methodologies and statistical approaches can vary, and we should not be surprised that some reports disagree, and that there are outright conflicts between toxicologists and epidemiologists (scientists that study patterns of health in populations). Regulators are aware of these shortcomings and often use safety factors to account for them. But those of us that use these products regularly, the message is simple: be cautious, and protect yourself.
Avoid Cross-Contamination
Disposable nitrile gloves are the product of choice for handling pesticides. But one of the most common problems with the use of gloves is cross-contamination. You’re handling product with your gloves on, touching containers, hoses, valves, and couplers. When you’re done, you climb back into the cab where you take off your gloves. Later, someone climbs up into the cab to talk to you, using the railing and operating the door handle without gloves. Guess what’s on their hands? Even later, you put away the hose without gloves and return to the sprayer. Now it’s on the steering wheel and all the levers. There are a few solutions:
- Double-glove so you can take the dirty outside glove off and still be protected.
- Wipe down surfaces that you might touch with gloved or bare hands daily.
- If using non-disposable gloves, avoid lined gloves and rinse the insides out daily.
Learn More
If you would like to learn more about pesticide safety, or to obtain pesticide application training, the Pesticide Applicator License can be obtained from the Ministry of Agriculture. This course offers in depth, valuable safety information for applicators, as well as general knowledge for pesticide applicators. The Pesticide Regulatory Directorate provides workers, employers, and the general public with a wide range of pesticide information. The PRD can be contacted from anywhere in Canada toll free at: 1-800-267-6315
Download this Quick Reference Guide for commonly used herbicides. Print, laminate and post it at the fill station or pesticide storage area for easy reference. Also, grab a copy of Health Canada’s “Stay Safe when using Pesticides” factsheet.
Sources
May 11, 2026

Sprayer Loading and the Jar Test

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 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, and understanding its role in pesticide performance is another article (or several). We’ve provided some links here for further reading.

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 fungicide 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.

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 filter 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

Keep agitation running throughout mixing and spraying. Aim for a “simmer” on the liquid surface rather than a “rolling boil.”

Low agitation can cause products to settle, making them difficult or impossible to resuspend later. Conversely, aggressive agitation (especially in half-full tanks) can cause foaming, pump suction loss, or product separation / clumping.

Pace

Adding products too quickly can cause product separation / clumping or poor suspension, leading to tank mix incompatibilities. While loading quickly improves operational efficiency, complex mixes require patience; Sometimes over five minutes between additions, especially in cold water or when using dry products.

To save time without sacrificing quality, consider pre-hydrating dry products or using a separate nurse tank to pre-mix loads for quick transfer. Remember: even if dry products look dissolved, they may still need more time.

Product formulation

Product formulation is a complicated science. In the 1950s 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 as many as 40 ingredients with formulation testing lasting two to four years! Generally, only 25% of the volume is water, 50% is active ingredients and the remaining 25% is co-formulants. This is why the more products you add to the tank, the higher the risk of antagonism. This is also why operators should carefully consider the cost benefit of generics, which may include the active ingredient, but do not tend to include the co-formulants.

Illustration based on a slide by Dr. Samantha Francis, Formulation & Application Technology Lead at the Syngenta Honeywood Research Facility.

Mixing order

Tank mixing order is critical for chemical compatibility. While common acronyms like w.w.w.W.A.L.E.S., W.A.M.L.E.G.S., and A.P.P.L.E.S. serve as reliable guides 95% of the time, always defer to the pesticide label for specific instructions.

Expanded generic mixing order:

Water: Fill tank 1/2 full (or 3/4 if fertilizer carrier).
Agitation
Water-Soluble Bags (WSB): Allow to fully dissolve.
Wettable Powders (WP)
Water Dispersible Granules (WDG, WG, SG)
Liquid Flowables (F, FL, SC, SE, CS, DC, EW)
Emulsifiable Concentrates (EC, MEC, OD)
Solutions (SN, SL, Liquid Fertilizers/Micronutrients)

Adjuvants:

Water Conditioners (e.g. anti-foamers, compatibility agents): Add before pesticides.
Activator Surfactants (e.g. NIS, COC): Add after pesticides or by formulation type along with pesticides.
Drift Retardants: Add last.

Examples of mixing errors

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 in the late 2010s, and working with the registrants, we found 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.

Mixing errors are just as likely in small plot work as in commercial sprayers. Watch this short video by Mike Cowbrough describing his experience with mixing order for Elevore and glyphosate.

The jar test

A jar test is a small-scale version of tank mixing used to check for physical incompatibility. Always wear PPE and work in a well-ventilated area away from ignition sources.

Jar test steps:

Prepare: Read all labels for formulation details, water quality requirements (pH/hardness), and mixing order. Shake liquid containers to ensure consistency.
Initial Carrier: Fill a 1-litre glass jar with 250 ml of water (or 375 ml if using oil/fertilizer).
Add Products in Order: Add chemicals following the standard mixing sequence, stirring constantly. Scale rates to match your tank concentration (e.g., 1 kg per 1,000 L equals 0.5 g in a 500 ml test).
Wait and Observe: Allow 3–5 minutes between additions—especially for dry products—to ensure full dispersion. If testing water-soluble bags, include a small piece of the film.
Final Volume & pH: Top the jar up to 500 ml with your carrier. Check the pH with a digital meter and add adjusters if required by the label.
Evaluate: Let the jar stand for 15 minutes.

The mix is likely incompatible if it generates heat, forms gels or scum, or if solids settle out (excluding wettable powders). Note: Jar tests only identify physical issues; they do not guarantee biological efficacy or crop safety.

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.

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

Records and delayed reactions

Maintain detailed mixing records for traceability and to track performance. These records help you replicate successes and avoid future failures.

Labelled jar tests are also valuable; by leaving them in the chemical shed overnight, you can see if products separate or solidify over time. This indicates whether a mix can safely sit in the sprayer or if it requires immediate rinsing. For example, one grower’s Enlist and Manzinphos mix appeared fine until it sat during a rain delay. It turned into “lard,” clogging the entire system and requiring a manual teardown. They even had to dig some of the substance out with screwdrivers (see the picture of the filter below). An overnight jar test likely would have predicted this problem.

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. They have great potential to 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”. Finally, if you have questions about a specific product, contact the manufacturer, who have likely already performed the testing with common tank mix partners and can advise you.

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

May 6, 2026

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
February 9, 2023
Spray Drift Basics
This article is intended as a basic overview of what pesticide spray drift is and how to avoid it. If you want a more in-depth study of the physics of drift, head over here.
Defining Drift
Pesticide spray drift is the aerial movement, and unintentional deposit, of pesticide outside the target area. Aside from being illegal, there are a lot of compelling reasons for avoiding it. Drift can be measured in financial loss associated with wasted pesticide, wasted time and reduced crop quality/quantity. Plus, if an application is unsuccessful, the operator may have to re-apply, incurring further cost. Pesticide drift increases any risk of damage to human health, susceptible plants (e.g. adjacent crops), non-target organisms (e.g. wild and domestic animals, pollinating insects, etc.), the environment, and property.
We’ll limit our definitions to two forms of pesticide spray drift: Particle Drift and Vapour Drift.
Physical Drift is the initial off-target movement of pesticide droplets. This occurs at the time of application, and it is generally on a scale of tens-of-metres. There is a secondary component to physical drift wherein particularly small droplets (or the evaporated remains of droplets) stay aloft for longer periods of time, during which they can move laterally with wind or vertically with thermals and turbulence.
Vapour Drift is the off-target movement of pesticide vapours. This is a function of product chemistry (vapour pressure) and surface temperature. Rainfall (rewetting) can also affect vapour loss. If vapour gets caught up in a light breeze, moves downhill during a thermal inversion, or is redistributed in precipitation, movement is can be on a scale of kilometres.
Managing Drift
Drift cannot be entirely eliminated, but sprayer operators can greatly reduce the degree and impact. Much of what follows relates predominantly to particle drift from horizontal boom sprayers, but it’s never wrong to follow these best practices. Research and modeling have shown that the three biggest factors under the operator’s control are:
- Apparent wind speed (i.e. the sum of wind speed and travel speed)
- Boom height (i.e. release height)
- Droplet size (i.e. nozzle spray quality)
Therefore, the degree and impact of drift can be greatly reduced by following these guidelines:
- Reduce the distance between nozzle and target. For a herbicide application, that means lowering the boom to the lowest practicable height. There are exceptions, but a good rule of thumb is that the boom height should be approximately the same as the nozzle spacing.
- Use the coarsest effective droplet size, generally achieved through the use of drift reducing nozzles such as air induction.
- Work with the weather. Labels will specify appropriate weather conditions for spraying. Change sprayer settings to account for hot, dry and windy conditions or halt the job until conditions improve. Generally, avoid spraying when the weather is against you.
- Identify any vulnerable nearby crop, landscape or environmental area. Choose a spray day when winds are blowing away from these sites. Explore voluntary watchdog sites like DriftWatch to see if there are registered sensitive crops nearby. Planting windbreaks or utilizing riparian areas can also help manage wind and provide localized downwind protection.
- Observe labelled buffer zones and recommended sprayer settings. In Canada, using optimal sprayer settings in the right environmental conditions may reward the sprayer operator with buffer-zone reductions.
- Work with your neighbours. Let them know your intentions. For example, greenhouse growers need to be notified to close vents during morning spray times to avoid any possibility of drift.
- Understand the potential damage off-target herbicides can cause and make this part of your planning when selecting a herbicide. Where possible, choose herbicides with a low risk of volatility. Avoid products like dicamba near susceptible crops (grapes, tomatoes, peppers, sweet potato, tobacco, IP soybeans, etc.) or greenhouses. While not necessarily volatile, other synthetic auxins such as 2,4-D are extremely damaging to horticultural crops at very, very low doses.
Buffer zones or No-Spray zones physically separate the end of the spray swath for the nearest downwind sensitive area.
Consider planting windbreaks between your operation and sensitive downwind areas. Be aware that the windbreak should slow and filter pesticide-laden air, not block it completely (~50 % porosity). Also be aware that there are potential impacts to nearby crop rows, such as creating shade as well as cool, still air conditions. Contact your local Nature Conservancy to discuss the right plants and management plan for you.
Running an Airblast Sprayer?
For airblast sprayer operators, the environmental factors that affect drift are the same, but the rules for optimizing sprayer settings are slightly different. Droplet size is less of an issue, and in some cases droplet size cannot be controlled. Air settings are the primary tool for reducing drift potential.
- Adjust fan settings to produce the minimal effective air speed throughout the season.
- Use deflectors to channel air into, not over or under, the target.
- If possible, increase droplet size by using air induction nozzles or disc & core (or disc & whirl) nozzles that produce a coarser droplet size. Depending on canopy size, you could use them in every nozzle position, or only in highest nozzle positions.
- Any sprayer design the brings nozzles closer to the crop (e.g. tower or wrap-around designs) will reduce drift.
- Canopy sensors that turn boom sections on and off to match the size and shape of the canopy will reduce drift.
It’s not only field sprayers that drift. Photo Credit – G. Amos and D. Zamora, Washington State.
Monitoring airblast drift with ribbons and a tall pole with water-sensitive papers stapled along the length. This trial was run using only water so as not to expose the person holding the pole. Photo Credit – M. Waring, British Columbia.
If You Suspect Drift
If you suspect your crops or property have been damaged by pesticide drift, follow these steps (The contact info is specific to Ontario, so substitute your local authorities). The following information is based on this article in ONFruit which focuses on herbicide drift. Drift onto an organic operation would not necessarily cause visual injury, but steps are similar.
1. Diagnose the problem
- Is there evidence of a spray application (agricultural or vegetative management such as roadside spraying)? Look for wheel tracks, weed symptoms, boom patterns and overlap on the headlands. Look for spray evidence in neighbouring fields, lawns, ditches, etc.
- Familiarize yourself with the symptoms of drift injury on your crops.
- Eliminate other possible causes. Disease, insects, nutrient deficiency, herbicide carryover, improper sprayer cleanout, and environmental stress can resemble drift injury.
- Are there damage patterns? In the case of physical drift, damage is more pronounced on the upwind side of the damaged area, tapering away with distance from the source. In the case of vapour drift, damage can be uniform throughout damaged area and not necessarily downwind from the source. Pesticides can also move in cold air drainage and in surface run-off from rain events. If damage is patchy, it may be something else, such as soil pH or carryover (look where sprayer starts and stops).
2. Contact the appropriate people
- Talk to your neighbour or the sprayer operator. Ask what was sprayed, when it was applied and who performed the application.
- Contact the Ministry of the Environment, Conservation and Parks District Office or Spills Action Center (SAC): 1-866-663-8477. The SAC is available 24/7 and they will then contact the appropriate Environmental Officer and pesticide specialist in your region. Local MECP offices can be found here.
  - It is extremely important to report as soon as possible because the concentration of herbicide drops quickly within the plant. Do NOT wait until there are symptoms. Do NOT hesitate to call, even if you are unsure if it’s pesticide drift.
- MECP officers can do a site visit, take samples of tissue and soil, and have them analyzed for suspect pesticides. Where appropriate, the offending applicator may face charges under Ontario’s Pesticides Act. Charges will be pursued only if off label use is identified from the information gathered.
  - Because of the wording of some of the labels and the difficulty of tracking down all the information needed, this has always been a very difficult thing to pursue in grower-to-grower drift incidents.
  - The results from the MECP lab are available for the grower and, if enough information is collected, the grower is encouraged to pursue civil court if insurance and/or cooperation with the applicator does not work. According to the label of most pest control products, the applicator is liable for any damage caused by the misapplication of a pesticide.
- Contact your (crop) insurance adjustor and advise the applicator to contact theirs. However, do not rely on your crop insurance; Insurance companies may not provide coverage for drift incidents. It is prudent to determine if you are covered before you need to file a claim.
- Report the incident to the PMRA Voluntary incident reporting system
- Report the incident to the manufacturer of the pesticide product. See the label for the toll-free number. Labels can be found on the PMRA label search.
3. Document all details of the problem and consider lab analysis
- Collect spray records. This includes yours (to ensure it was not your application), and the potential offending applicators’.
- Collect weather records (temperatures, possible temperature inversions, wind speed, wind direction, rainfall) for the date of application).
- Take timestamped, geolocated photos (most smartphones include this information automatically, but check your settings). Repeat photos several times through the season.
- Document yield loss from the damaged area and an undamaged area. Choose a similar planting (same age, cultivar, rootstock, etc.). For perennial crops (e.g. vineyards, orchards, asparagus, berries) herbicides such as Group 4’s may necessitate documenting the effects for several years after the damage occurred.
- Laboratory analyses of herbicide levels in plant tissue are often necessary to confirm the presence of herbicides, although symptoms may be helpful in diagnosing which herbicides caused the problem.
  - Research laboratories that will analyze crop samples for herbicide residues. Their requirements regarding sample size, labeling, storage, and shipping will vary, as will the list of pesticides they provide testing for and their minimal detection levels. Given the time-sensitive nature of pesticide detection, it would be prudent to know this information before need the service.
Applicator Liability
Anyone using pesticides is responsible for their safe application. For example, the Ontario Pesticides Act requires that licensed spray applicators carry a specialized liability insurance policy that provides appropriate coverage for their business. Operators who work on a “for hire” basis (e.g. a licensed spray applicator) or away from their own farm operation will need additional coverage. Where drift damages adjacent crops, insurance adjustors generally ask the following questions:
- Was the damage to the applicator’s own crop? If so, it is unlikely that there will be coverage under any insurance policy.
- Was the damage to a neighbour’s property? If so, the applicator’s liability policy may respond.
- Was the product being applied according to label directions?
Other Resources
Managing spray drift is everyone’s responsibility. Extremely low, and often invisible, amounts of spray drift can be very damaging; even long after the application. For more information about drift mitigation, watch the following videos and download a copy of this Factsheet.
What is Pesticide Drift?- Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs (2011)
Equipment and Methods to Reduce Pesticide Drift- Ontario Ministry of Agriculture and Food and Ministry of Rural Affairs (2011)
Preventing Pesticide Spray Drift- University of Missouri Extension (2013)
Three simple ways to reduce drift. Thanks to Real Agriculture for filming and editing! (2014)
Three simple ways to reduce drift. Thanks to Real Agriculture for filming and editing! (2014)
September 19, 2022
How Canadian Crop Protection Products are Assessed for Safety
As originally published by The Grower, August 2020.
Pests such as insects, diseases, and weeds can affect our quality of life in many different ways. Pests can represent a threat to public health and the environment as well as create substantial negative impacts to the economy if they are not sufficiently managed.
Crop protection products or pesticides play an important role in agriculture and other sectors in managing pests. These products can be very broad in scope; they include, as defined by the federal government:
“A product, an organism or a substance, including a product, an organism or a substance derived through biotechnology, that consists of its active ingredient, formulants and contaminants, and that is manufactured, represented, distributed or used as a means for directly or indirectly controlling, destroying, attracting or repelling a pest or for mitigating or preventing its injurious, noxious or troublesome effects.”
While dealing with pests is an important aspect of society, crop protection products can also represent a hazard. If not properly managed, their use has the potential to pose risks to the health and well-being of Canadians and to our environment. As such, crop protection products are highly regulated. So how do we ensure the safety of these products in Canada?
The federal government has the responsibility of reviewing and registering pest management products before they can be sold or used in Canada. This is covered by the Pest Control Products Act (PCPA). The primary objective of the PCPA is the prevention of unacceptable risks to human health and the environment resulting from the use of these products. The PCPA also recognizes that pest management is an important factor to both the economy and quality of life in Canada; however, these are considered secondary objectives to health and the environment.
It is the mission of the Pest Management Regulatory Agency (PMRA) based in Ottawa to execute the implementation of the PCPA and its objectives. Of the 450 employees at PMRA, 73% are scientists, including biologists, toxicologists, epidemiologists, and chemists. Evaluations of products by PMRA are extensive and use a weight of evidence approach that considers the nature and quality of scientific sources in their decision making.
Before the PMRA approves any product for use, regardless of origin, it must undergo a thorough science-based risk assessment and meet strict health and environmental standards. If the proposed use of a product poses unacceptable risks to human health or the environment, it is not registered for use in Canada. It is the responsibility of the company or individual seeking registration to prove their product does not pose unacceptable risks through scientific studies.
During evaluation or re-evaluation of a product, PMRA considers a comprehensive toxicology database to assess potential health effects. Both shorter term and longer-term effects are considered. These include, but are not limited to, studies to characterize acute and chronic toxicity, carcinogenic potential, reproductive and developmental toxicity, immunotoxicity, neurotoxicity, genotoxicity, and endocrine disruption potential. The PMRA assessments are also informed by epidemiological evidence, general scientific knowledge, and published scientific information.
In exposure assessments, sensitive populations and life stages are specifically addressed, including infants, children, and women of child-bearing age. Consideration is given to different activities, dietary habits, food intake, and body weight of children versus adults. A product will only be registered if this estimated exposure raises no concerns. Once this is determined, the PMRA will ensure the label directions indicate the appropriate use instructions to best minimize exposure.
Exposure to a product may occur through different routes (oral, dermal, and inhalation) and pathways (dietary, drinking water, and non-commercial uses). In order to fully assess potential risks, the PMRA conducts aggregate assessments which consider these different pathways and routes. Where it has been demonstrated that a group of pesticides share a common mechanism of toxicity, they are subject to a cumulative risk assessment in which the combined aggregate risks are assessed. In occupational settings such as agriculture and forestry, exposure may occur while handling or applying pesticides. As well, workers re-entering treated areas may be exposed to pesticide residues. These occupational risks are also assessed during the PMRA review.
The PMRA also sets science-based maximum residue limits (MRLs) on food commodities to ensure the food Canadians eat is safe. These limits are enforced by the Canadian Food Inspection Agency. The MRLs established for each crop are set at levels well below the amount that could pose a health concern.
Environmental risk assessment integrates the environmental exposure and ecotoxicity information to evaluate the potential for adverse effects on non-target species. This integration is achieved by comparing estimated environmental concentrations (EECs) with concentrations at which adverse effects may occur. The EECs are concentrations of product in various environments, such as in food, water, soil, and air. The EECs can be estimated using standard models, which take into consideration the application rate(s), chemical properties, and environmental fate properties, including the dissipation of the product between applications. In re-evaluations of registered products, EECs can be taken from empirical data.
Ecotoxicity information includes acute and chronic toxicity data for various organisms or groups of organisms from both terrestrial and aquatic habitats including invertebrates, vertebrates, and plants. Toxicity endpoints used in risk assessments may be adjusted to account for potential differences in species sensitivity as well as varying protection goals such as protection at the community, population, or individual level.
A vast amount of scientific data is reviewed when evaluating the safety of crop protection products in Canada. These extensive reviews are posted publicly and include consultations where any stakeholders are invited to submit comments. There is good reason to have high confidence that crop protection products are safe for Canadians and the environment under the conditions of registration.
For those who want a more in depth read, check out the PMRA’s guidance document overview.
September 15, 2021