Saskatchewan Agriculture’s weed control specialist is concerned that improper use of pre-harvest herbicides containing glyphosate could lead to the chemical getting into the seed.
Glyphosate is a systemic herbicide that moves throughout the plant to control perennial weeds, said Clark Brenzil.
But, as plants mature, much of the energy resources in the plant are shuttled to the developing seeds and systemic glyphosate circulating in the plant is also directed to and concentrated in the seed.
“A new formulation of gly-phosate containing a small amount of glufosinate is called Roundup Fast Forward. It is intended to accelerate dry-down of green weeds so they do not interfere with harvest operations. But application of any product containing glyphosate prior to 30 percent kernel moisture is undesirable for several reasons,” he said.
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Plants with more moisture will take up excessive amounts of gly-phosate into the seed. In this way, glyphosate residues enter the food chain, or crops intended for use as seed will, when planted, have reduced emergence and less vigor in the plants that do emerge.
“Furthermore, plants that are not sufficiently mature may actually interfere with spray penetration to lower areas of the crop canopy. And this reduces weed control,” said Brenzil.
Reglone is the only registered desiccant on the market today, said Brenzil.
“A desiccant is used to hasten crop maturity, typically in non-determinant crops. And Reglone is still the only registered desiccant,” he said. “Desiccants are not systemic; they do not move in the plant to the seed, thereby keeping chemical residues from entering the seeds.
“The new product, Gramoxone PDQ, is not registered for use as a dessicant either. It does not work as well as Reglone for accelerating the maturity of broadleaf crops such as pea and lentil. In addition, this new product has not been tested for the possibility of food residues in harvested grain so there is another concern as well,” said Brenzil.
Trent Catley, of Saskatchewan Agriculture said farmers should remember the unregistered use of a pesticide is a violation under The Pesticide Control Act.
“Both federal and provincial pesticide officers are investigating all reports of this illegal activity,” he said.
