Staging critical for pre-harvest glyphosate

The crop must be mature before applying the non-selective herbicide

“Glyphosate is not a desiccant.”

And just to be sure listeners got the message Manitoba Agriculture cereals specialist Pam de Rocquigny repeated the statement again during the Westman CropTalk webinar July 27: “Glyphosate is not a desiccant.

“I no longer want to see anyone referring to when they are applying a pre-harvest glyphosate application… that they are desiccating their crop,” she added. “They are not. It is not a desiccant.”

While applying glyphosate to cereals can result in earlier harvesting, it does not cause kernels to ripen faster, de Rocquigny said.

Glyphosate shouldn’t be applied to wheat until it’s in the hard-dough stage and kernel moisture content is less than 30 per cent. Earlier applications can result in lower yields and bushel weights and glyphosate residues exceeding approved levels, which could prompt buyers to reject the crop.

“Staging for pre-harvest (glyphosate) is really critical,” de Rocquigny said. “You are actually applying it when the crop is physiologically mature.

“The final yield has been determined at that point.”

Farmers should also check with buyers before applying pre-harvest glyphosate, she added. Most maltsters don’t want barley treated with the non-selective weed killer and some oat buyers have the same policy.

Seed growers shouldn’t apply pre-harvest glyphosate either because glyphosate can reduce germination.

to pre-harvest glyphosate and done when wheat is also in the hard-dough stage, de Rocquigny said.

“There are pros and cons to swathing,” she added. “Grain in the swath can be more prone to pre-harvest sprouting under adverse weather conditions. A standing crop will weather a little bit better, but swathing is still an option out there available to producers.”

If glyphosate is applied before the crop is mature the herbicide taken into the plant can be transferred to the seed resulting it glyphosate levels exceeding the allowed maximum residue limit — a concern that’s growing among end-users and grain companies.

“Any time… things are on the radar they tend to check a little bit more closely,” de Rocquigny said. “So if you are planning a pre-harvest glyphosate application… you definitely have to make sure you are applying it at the right staging. It’s better to go a little late than a little too early.”

About the author


Allan Dawson

Allan Dawson is a reporter with the Manitoba Co-operator based near Miami, Man. Covering agriculture since 1980, Dawson has spent most of his career with the Co-operator except for several years with Farmers’ Independent Weekly and before that a Morden-Winkler area radio station.



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