Producers concerned about what would happen if they could no longer apply the herbicide to their crops before harvest
Harvesting lentils has become complicated with the increased sensitivity to pesticide residue by international buyers of the pulse crop.
Some grain buyers will not accept lentils treated with pre-harvest glyphosate due to scrutiny in the global marketplace and low maximum residue limits .
Ideally, using a desiccant including diquat, Reglone, will provide an adequate dry-down of the crop so that growers can quickly take it off with straight cut harvesting.
However, lentils are not a competitive crop, and glyphosate is much more effective than a desiccant in taking out large weeds before harvest.
“The most effective timing for perennial weed control is in the fall pre-harvest with those glyphosate applications,” said Sherrilyn Phelps, agronomy manager as Saskatchewan Pulse Growers.
“It also helps to control some of those bigger weeds, where if you went in with a desiccant to get them, to dry them down when they are big and green and healthy and growing actively, it doesn’t work as well.”
Glyphosate is a cheaper option compared to desiccants, and a timely pre-harvest application of it can take a big bite out of populations of perennials such as thistles or dandelions for a few growing cycles.
There are also tank mix options with a saflufenacil such as Kixor or Heat with glyphosate, and while this is a more expensive option it can be extremely effective, especially on weedy fields.
“The Heat helps to speed up the dry-down and with the glyphosate you would get the weed control,” Phelps said.
Glyphosate is an effective and cost efficient harvest management tool, and some growers have told The Western Producer they would rather not grow lentils if they can’t use the product to help with harvest.
This is partially because if a farmer does get into trouble with weeds in their lentil crops, it can be difficult to harvest without glyphosate, and swathing lentils is not a desirable option to get the weeds to dry down before running the crop through the combine.
“You have to cut them fairly close to the ground, so if you try to swath them there isn’t enough stubble to keep them in place. So they are very susceptible to wind and to blowing,” Phelps said.
“And if the swaths do get wet, then it just takes that much longer to dry out, and you can get downgrading in terms of grade and quality.”
She said there are a few growers who swath lentils in the province, most often when they are saving the seed to use on their farm. Swathing lentils can also help retain a nice colour in the seed and help with grading if the swaths do not get rained on.
However, crops harvested with a desiccant or pre-harvest glyphosate application can also reach a top grade, and most growers in the province are set up to direct combine the crop.
Most buyers do accept deliveries of lentils that have had a pre-harvest glyphosate application, as long as the label has been followed.
Of utmost importance is that growers wait until the seed is pretty much at physiological maturity with less than 30 percent moisture in the seed in the least mature part of the field.
“If it’s above 30 percent moisture, there is a higher risk of more product moving into the seed,” Phelps said.
“The seed has still got a fairly high moisture content and is connected to the pod, the pod is connected to the plant, and glyphosate is systemic so it moves within the system within the plant and it can move into the seed.”
She said growers should also pay attention to the pre-harvest intervals of all the crop protection products they apply.
The pre-harvest interval for glyphosate is seven days.
Growers should also find out the specifications of the company they intend to sell their lentils to so that they understand their specifications and those of the countries to which they sell.
For a pre-harvest application staging guide for lentils, visit keepingitclean.ca/lentils/staging-guide.
Sask Pulse has developed a lentil staging guide that can be found here.