Consider market access when timing pre-harvest applications. 

Ag retailers have a vital role to play in keeping domestic and export markets open for Canadian producers, particularly where pesticide residues are concerned. By ensuring staff and customers are well informed about label directions for product use, retailers can provide tremendous value by minimizing the risk of unacceptable residues and preserving crop marketability for their customers.

Key to protecting that investment is always using the product as directed on the label, including only using it on the crops it is registered for, correctly timing the application and strictly adhering to the pre-harvest interval (PHI).

“Pre-harvest intervals are set to ensure the active ingredient has enough time to dissipate and not leave unacceptable residues,” says Clint Jurke, agronomy director with the Canola Council of Canada. “It is critical to observe the interval on the label because once the crop is cut, those residues can remain on the harvested seed.”

Knowing Your PHI

When planning their use of inputs at any time, and especially later in the season, growers should be aware of the PHI for each product they will be applying. Also known as the spray to swath interval, the PHI outlines the number of days that must pass between product application and swathing or straight-cutting the crop.

PHIs can vary greatly between products – from as little as one day to over 60 days. By reinforcing adherence to the label, ag retailers can help make sure their customers aren’t caught in a late-season bind if they cut too soon after spraying.

“This year, planting was a bit behind schedule across the southern parts of the Prairies, which often compresses the application window,” says Jurke. “As growers try to meet their harvest goals, it’s important to always stick to the PHI to avoid leaving unacceptable residues and keep their crops ready for market.”

Another situation to consider is if growers face a late-season pest threat to their crop. “If there’s a problem that presents in the field as swathing approaches, obviously growers will want to protect their yield and investment and may feel compelled to spray to manage that issue,” he says.

The closer the field is to swathing, the more limited the choices for pesticides based on the PHI. For more detailed information, Jurke recommends retailers direct their customers to, which includes the latest information on MRLs and best practices to keep markets open for Canada’s canola and cereals. In addition, canola growers can visit, an interactive interval tracking tool.

“ is a great tool for canola growers. Growers can either enter the product they sprayed to see how many days they need to wait after application, or, they can enter their planned cutting date to find a product that is still safe to apply,” says Jurke, adding, “It can even sync with the calendar on your smart phone.”

Pressing Pause on Glyphosate Applications

Giving good recommendations that prevent or reduce residues, and possibly lost revenues, will help retailers build their reputation with their customers and protect the reputation of Canada’s crops. Karen Churchill

For pre-harvest glyphosate applications, cereal growers face the opposite issue when it comes to timing. The key to pre-harvest glyphosate application is to wait to spray until the greenest part of the field has reached 30 per cent seed moisture content or lower. If producers spray glyphosate too early, when seed moisture levels are above 30 per cent, traces of the product can be absorbed by the seed as it dries, leaving unacceptable residues behind.

“Retailers should encourage their customers to pay very careful attention when applying glyphosate pre-harvest,” says Karen Churchill, director of research and market support with Cereals Canada. “When applied correctly, glyphosate is safe. However, it has come under increased scrutiny compared to other pesticides and applying glyphosate too early can result in residues that exceed acceptable maximums, risking market access.”

Churchill says one challenge growers face when timing glyphosate applications is uneven maturity in the field. Growers may want to spray when the bulk of crop is ready, but if the greenest part of the field isn’t mature enough, residues could contaminate the entire lot and make it unfit for markets.

To account for uneven maturity, it’s important to check the entire field before making the decision to spray. Ensuring the least mature part of each field is ready to receive treatment protects the marketability of the entire crop.

“For ideal glyphosate timing, there is a quick in-field test to make sure kernels have reached the hard dough stage,” says Churchill. “At this stage, when you press a thumbnail into the kernel, it will leave an indent. If the indent bounces back, the crop is not dry enough to spray glyphosate.”

By helping their customers time product applications and use products correctly, retailers can help ensure this year’s crop is accepted by all customers. “Giving good recommendations that prevent or reduce residues, and possibly lost revenues, will help retailers build their reputation with their customers and protect the reputation of Canada’s crops,” says Churchill.

Visit for updates on MRLs throughout the season.

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