It will soon be time to kill that winter cereal cover crop to make room for your spring cash crop.
But unless you have been living under a rock, you know that glyphosate and Liberty (glufosinate) are expensive — and, more importantly, in very short supply.
If you’re fortunate to have some glyphosate, or you’re going with an alternative like Gramoxone, or paraquat, here are some tips from John Wallace, a Penn State University weed scientist; and Dwight Lingenfelter, Extension weed educator:
For glyphosate, avoid tankmix antagonism. Wallace recommends against tank-mixing glyphosate with clay-based herbicides like WG, DF, DG and F, and to go with low carrier volumes of between 10 and 15 gallons per acre.
He also recommends adding ammonium sulfate (AMS) at between 4 and 8 pounds per 100 gallons. AMS is effective at reducing the effects of hard water cations on glyphosate, which can make the herbicide less effective.
If you are tank-mixing with a clay-based herbicide, Lingenfelter recommends increasing the glyphosate rate by 20% to 25% to overcome the potential effects on the glyphosate.
As glyphosate-resistant marestail continues to spread, Lingenfelter recommends tank-mixing, but using multiple modes of action.
Optimize uptake. Wallace recommends using non-ionic surfactants (NIS) to increase spray retention and to avoid spraying when there is excessive dew.
He also recommends spraying when there is plenty of sunlight and high humidity, as this will optimize translocation of the herbicide: its ability to move around.
Gramoxone tips. If you’re going with a nonglyphosate burndown, like Gramoxone, many of the opposite things are true.
Wallace says that it is best to synergize Gramoxone with tankmix partners like atrazine and metribuzin. It’s also best to use high carrier volumes — greater than 20 gallons per acre — and to use medium-size droplets.
Lingenfelter recommends using flat fan-nozzle tips that produce medium to coarse droplets, and a uniform spray pattern and thorough coverage for best results.
Air induction nozzles can be used, he says, but increase the spray volume to 20 gallons per acre.
It’s also important to use a clean water source, he says, as soil or sediment can reduce Gramoxone activity.
Get them early this year. With glyphosate in short supply, Lingenfelter says size will matter when it comes to terminating cereal cover crops.
“I suggest terminating them earlier, when they are smaller, this year, to get better control with the lack of glyphosate. If they are not fully terminated in the burndown, they can be very difficult to control in the crop — especially corn without glyphosate,” he says.
On the supply side, Lingenfelter doesn’t expect things to get better for a while.
“In general, things are turning out pretty much the way it has been predicted with herbicide supplies. As far as glyphosate and glufosinate supplies … they are still very tight. Some of the Group 15 products like metolachlor and acetochlor are getting limited. 2,4-D and triazines, especially simazine and atrazine, are very difficult to obtain in many locations. Keep in mind that some dealers were able to secure some of these products last fall, and have a moderate supply, while others are not as fortunate,” he says. “Due to supply constraints, we are also hearing about some dealers that are only selling product to those they have worked with in the past, and are thus not able to sell product to new customers.”