Wheat School: Timing a Pre-Harvest Glyphosate Application Right

With high fusarium levels threatening the quality of this year’s wheat crop, Peter Johnson, cereal specialist with the Ontario Ministry of Agriculture and Food, is urging farmers to take the grain off early so as to minimize the growth and spread of the disease.

That’s all good and well, say farmers, but the crop is still quite green. Can I spray it with glyphosate to speed up the dry down process? Well, yes and no. As Johnson outlines in this video, a pre-harvest glyphosate application is only safe if done once the crop has reached physiological maturity so that none of the chemical will translocate to the kernels. How do you know when the wheat is, in fact, physiologically mature? There are two indicators: stem colour and the thumbnail imprint test. Johnson walks you through both in the video below.

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RealAgriculture Agronomy Team

A team effort of RealAgriculture videographers and editorial staff to make sure that you have the latest in agronomy information for your farm.


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Betsy S

I am assuming that organic wheat gets no glysophate spraying at all, either before spraying or during any maturation of kernels. That is what I am counting on.


So putting Glyphosate on Plants pre harvest is dangerous because it gets in the plant cells. Then why are we using Glyphosate on all the staple crops in the USA pre harvest ? GMO crops get RoundUp sprayed on them multiple times . If you buy GMO Free Organic they do not get sprayed with Glyphosate.

Lyndsey Smith

The concern with a too-early glyphosate application is an agronomic one, not a food/human safety issue.

Sprayed too early, and the glyphosate translocates (moves to) and impacts the kernel’s ability to germinate. This is an issue if the seed were destined to be used to plant the next crop (it wouldn’t work very well) and it negatively impacts yield. All crops are held to strict maximum residue limits (MRLs). A crop sprayed with glyphosate must meet these limits.


What are the limits? What scientific study determined what is an acceptable level of toxins in the wheat? How do you control when the farmer sprays?

Andrew Jensson

As Larry has stated, what is your evidence that glyphosphate is not a food/human safety issue?


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