By Mitchell Japp, MSc, PAg, Provincial Specialist, Cereal Crops, Regina
Another year, another knock against using pre-harvest glyphosate. Richardson Milling announced they will be sourcing oats that have not been treated with pre-harvest glyphosate. In 2015, Grain Millers announced they would no longer be buying oats treated with pre-harvest glyphosate. Malt barley buyers have had a long standing moratorium against the use of pre-harvest glyphosate. What is behind this trend? Which crops can pre-harvest glyphosate still be used on?
When Grain Millers stopped purchasing oats treated with pre-harvest glyphosate, they indicated that they were seeing issues in the mill due to the glyphosate. So, product performance is a concern that buyers have, although recent research found no measurable effect in oat quality when glyphosate is applied correctly. Richardson Milling indicated that consumer demands are driving their decision. Oats are included as an ingredient in several food products and when some of those products were tested, the labs were able to detect glyphosate residues, albeit well below maximum allowable levels set by federal regulators based on available science. Some consumer groups want zero residues, so it is bound to impact purchasing decisions.
What has never been clear in the discussion, is if we are talking about the registered use of glyphosate as a pre-harvest weed control herbicide or the often used, but inaccurate and off-label use as a so-called desiccant. Glyphosate is registered for pre-harvest weed control in most cereal crops but it is not registered as a desiccant.
When applied correctly, as defined on the label, all the grain will be at physiological maturity. Correct staging for cereals is at 30 per cent grain moisture content. At this stage, the grain is physiologically mature and is no longer receiving water or nutrients from the plant. So, there will be no translocation of the glyphosate into the grain. In this case, residues will be minimal, mostly being removed with the hull during harvest or processing.
Application of glyphosate when the grain is not yet at physiological maturity, will lead to residue accumulation in the grain. Pre-mature application will lead to decreased test weight and decreased performance. Watch those late tillers and low-lying areas – those are the ones that are holding up harvest and it can be tempting to use glyphosate to even things up in the field. Though with more and more buyers requiring oats and barley with no pre-harvest glyphosate applied, it may not be long before the legitimate uses of this harvest management tool are eliminated.
Careful management of pre-harvest glyphosate used only for weed control, when the whole crop has reached the required stage, will result in minimal levels of glyphosate in grain samples. Public surveys show that farmers are held in high regard. Managing pre-harvest glyphosate correctly, as outlined on the label, is a way to "do the right thing," an integral component of public trust. Information on how to get your cereals ready for market are available online.