Herbicide use can be needlessly complicated

Once you’ve chosen an in-crop herbicide, the most basic question is how many acres per jug or per litre. All too often, it’s difficult to find the answer.
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Herbicide use is more complicated than it needs to be. The trouble starts with units of measure and extends through to recommended practices.

Once you’ve chosen an in-crop herbicide, the most basic question is how many acres per jug or per litre. All too often, it’s difficult to find the answer.

Yes, rates vary for some products based on the crop and the weed spectrum so the answer isn’t always straight forward.

However, don’t provide rate info in grams of active ingredient per hectare. First of all, nobody in Western Canada uses hectares. Second, don’t make people do the calculation of grams per litre to figure out how many litres per acre.

A few products have it right. For instance, Corteva on its herbicide OcTTain XL has this prominently on the box:

“For in-crop uses, this 2 x 9 L case treats 40 acres (16 ha). One 9 L jug treats 20 acres (8 ha). OcTTain XL is rainfast in 1 hour.”

This is the info you need. On most products, the box has no rate info. You have to wade through the fine print of the label past page after page of safety instructions telling you not to drink the stuff and don’t splash it in your eyes before finally finding the recommended rates expressed in a manner that requires a calculator to figure out. It’s amazing more mistakes aren’t made.

Thank goodness for the guides to crop protection published in each province. They are a critical source of information on the myriad of chemistries available. While a lot of work goes into the guides, they can be maddening for what they don’t tell you.

On tank mixes, the Saskatchewan guide stops short of telling you the correct order of products going into the tank. Instead, readers are told to check labels of products to be mixed for directions. Good luck finding that. The guide does have general guidelines if you can figure out if the products are oil dispersions, emulsifiable concentrates or flowable liquid suspensions.

The Saskatchewan guide makes an attempt to explain sprayer clean-out procedures based on the type of products that were in the tank. While some useful guidelines are provided, the clean-out procedures are far more arduous than what happens in the real world. Who actually scrubs their nozzles and screens with an old toothbrush and does five or six different rinses as the guide recommends?

Because sprayers are made for the American market, spray tanks are measured in U.S. gallons. If someone tells you the tank of their sprayer is 1,000 gallons, in all likelihood it’s American gallons.

The Saskatchewan crop protection guide uses litres and for many products a water volume of at least 40 litres is stipulated. Many people equate 40 litres with 10 gallons, but it isn’t that simple. An imperial gallon is 4.55 litres. An American gallon is 3.79 litres. For an application rate of 40 litres per acre, it takes a little over 10.5 American gallons.

Recently, I traded up to the next sprayer model. I punched in the tank volume in litres like I had always done in my old sprayer and then went to set the rate. The rate in the controller from the previous owner was five. Obviously, this wasn’t five litres per acre; it was five gallons per acre. I went back and changed the tank volume to gallons so that everything would match.

Just another complication in an already confusing world of crop protection products.

Kevin Hursh is an agricultural journalist, consultant and farmer. He can be reached by e-mail at kevin@hursh.ca.

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