• It is critical that the cotton and soybeans are Palmer amaranth free at planting.
• The bottom line is the crop must have a head start on the pigweed, not the other way around to have a chance.
• If the worst case scenario occurs and the pre-applied herbicide does not get activated and Palmer emerges with the crop, do you have the spraying equipment and labor to apply a post emergence application in a timely manner?
THREE-FOOT tall Palmer amaranth with viable seed on April 26.
The environmental conditions that allowed all the early planting are working against us from a weed management standpoint.
We have many starting to plant soybeans and cotton into soil that is dry. The hit and mostly miss showers of the last couple weeks do not bode well for getting pre-applied herbicides activated in these crops.
We have several reports of non-activated pre-applied herbicides in corn needing post applications to clean up weeds. In corn this is a problem.
In cotton and soybean fields infested with glyphosate-resistant Palmer amaranth, this is a huge issue. What can be done to help minimize this risk?
First, it is critical that the cotton and soybeans are Palmer amaranth free at planting. We just had a report of a, to be planted, cotton field in Hardeman county with a very thick stand of 2 to 3-foot tall Palmer amaranth.
The Palmer in this field had 12-inch long flowering branches with viable seed! Palmer this thick and tall cannot easily be either tilled or sprayed in order to remove the Palmer prior to planting. It will require sequential burndown treatments or a burndown followed by tillage in order to start clean.
The bottom line is the cotton must have a head start on the pigweed, not the other way around to have a chance to make a crop.
Second, if you have irrigation in these fields do not hesitate to cut it on and water in the pre-applied herbicide. A half inch of precipitation will enable a pre-applied herbicide to work every time.
Third, consider your post-emergence spraying capacity. If the worst case scenario occurs and the pre-applied herbicide does not get activated and Palmer emerges with the crop, do you have the spraying equipment and labor to apply a post emergence application in a timely manner?
These large modern air seeders and cotton planters can plant many acres of soybeans or cotton in a few days. In Roundup Ready or conventional soybeans can you spray a fomesafen product prior to pigweed reaching 3-inches tall across those same acres in about a 3 day window? If not, you may want to slow the planting process down.
In Liberty Link cotton or soybeans the post emergence window is wider to control pigweed, but still for best results it must be timely. If pre-applied herbicides fail to buy us any time this spring, the ability to spray post emergence applications in a timely manner will make all the difference.