By Tom Wolf

It’s an old mantra – read the label. And there are good reasons for that advice. The pesticide label represents the information required for the legal and safe application of the product. But the label is also full of bad information, including statements that require caveats and exceptions, particularly when it comes to application instructions. All too often, I find that some of the information is being misinterpreted by users.

It’s time for a frank discussion on the pros and cons of the modern pesticide label.

1. The important information isn’t easy to find.

Most applicators look to the label for crop and pest spectrum and staging, rates and water volumes, as well as rotational restrictions. Yet the label is front loaded with precautionary statements. I don’t want to downplay the importance of safe application, but unless there is unique and critical safety information to provide, place it at the end. It gets skipped regardless.

Then, provide the information in a logical order, perhaps in the chronology that a user might need: crops and stages; re-cropping intervals; pest species and development stage; rates; mixing order; application volume; buffer zones re-entry; and harvest interval. 

2. The units of measure are different from what Western Canadians use on the farm.

One of the fundamental rules of effective communication is to speak the language of your audience. If the registrant needs the product rates to be accurate, they should be allowed to communicate in the units of measure that the applicators use. Although I’m a proponent of the metric system because it makes every single calculation on the farm easier, I recognize that my clients use U.S. gallons for water volume, litres or grams (or “cases”) for product rates and acres for land area. So that’s what I use, too. But the label insists on units that are not commonly used in Western Canada. Conversions are required, and that’s a recipe for mistakes. The new Pest Control Products Act, for which consultations are starting, could address this issue. 

3. The cleanout instructions don’t make sense.

Tank cleanout and waste disposal are among the most pressing questions of any applicator. It’s important to get the tank and boom clean, and to achieve this in minimal time. Yet, many product label procedures require two to three full tanks of water and overnight soaking, being completely oblivious of the resources used to make that happen. In fact, many labels show no recognition of many common features on sprayers, such as wash-down nozzles or on-board clean water tanks. Applicators must therefore find their own methods of cleanout by trial and error. 

This isn’t entirely the fault of the label. Sprayer manufacturers have a myriad of configurations and automated processes for cleaning that can be confusing or wasteful. Furthermore, some formulations are notorious for being hard to clean and as a result cause widespread crop damage, even with a diligent cleaning.

4. Important information is missing.

The registrant provides certain information voluntarily. Rainfastness is one example. We may see it on a label, or we may not. The effect of cold temperatures is another. Only rarely does the label provide advice on the consequences of unexpected cold temperatures prior to or following application. Identifying re-cropping intervals sometimes require field bioassays. This is not helpful. 

5. What’s the best droplet size/spray quality to use for the product?

Most labels make reference to spray quality. But it’s not for the reasons some people think. Almost all references to spray quality are in the restrictions section, where buffer zones are identified. It is there that the label may say, “Do not apply in sprays finer than ASABE Medium.” This spray quality requirement is for drift control only and means that the Pest Management Regulatory Agency (PMRA) risk assessment for drift was based on this spray quality. It does not mean that the registrant believes the spray will work best with that spray quality. In fact, registrants very rarely make recommendations regarding spray quality for efficacy. Instead, they use statements like, “ensure thorough coverage.” without any specific indication of what the metric may be. This is one of the most important deficiencies in pesticide regulation. The absence of spray quality leaves the applicator unsure of how to ensure the best pesticide performance and may spray finer than necessary, risking drift. 

On many labels, the application information is badly dated, to the point that it should not be followed. A label that requires the use of a “flat fan nozzle at 40 to 45 psi” is asking the applicator to obtain old technologies that may be drift prone and to use these at pressures that are not compatible with modern rate controllers. For the past 20 years specialists have recommended low-drift nozzles, many of which require higher pressures to operate properly, all the while reducing drift. Another common label statement is to use sprayer speeds of six-to-eight kilometres per hour. While slower speeds can be valuable for improving uniformity and reducing drift, even I know to avoid recommending such slow speeds. 

The problem with such serious errors is that the credibility of the entire label suffers. The user doesn’t know which parts to take seriously.

6.    The mixing order on the label disagrees with the mixing order elsewhere.

Improper mixing order can result in incompatible mixes. Nobody ever talks about the proper way to dispose of a tank of sludge, probably because there isn’t one. This remains one of the more painful and troublesome aspects of a spray operation. 

The proliferation of tank mixes and the addition of speciality fertilizers and adjuvants such as pH modifiers can be a minefield. While the label does recommend the order in which the product is to be mixed and agitated, the introduction of tank mixes creates uncertainty. The complicating factors of poor water quality, cold water or product temperatures, and excessive agitation is known to generate issues for some mixes. It would be very helpful for these adverse outcomes to be reported and mentioned on the label.

7.     How sensitive is the product to water quality?

Spray water may contain a variety of solutes, have a unique pH and may also include suspended solids such as soil particles. Some, but not all, pesticides are sensitive to these properties. It is useful to identify if water shouldn’t exceed a certain maximum level of hardness, bicarbonates, pH, etc. Most of these limitations are known to the registrant. Let’s see these limits, and what to do about them, on the label.

The role of provincial guides to pest control

Provincial guides are compendiums of the label and are virtually indispensable to advisers and farmers alike. The format is much better, summarizing the pertinent information in a consistent order and format, while adding valuable summaries. A recent online version of the Western Canadian guides, InputsPro (, is a very valuable addition to the system for desktop or mobile platforms. 

Because these guides are based on labels, they must have fidelity to those original documents and that’s why the label formats themselves require revision. Guides do add some chapters on tank cleanout, adjuvant use and nozzle selection that is more up to date than the label. However, in a strictly legal sense the label itself must be followed, and its contravention may be an offense. It is hard to believe that such an important document would be so slow to reflect modern information and be so difficult to follow.