There have been a number of reports of Palmer amaranth up with newly emerged soybeans and cotton. There are various reasons for this development.  The number one reason is pre applied herbicides were not activated by rainfall and the pigweed emerged with the crop. One consultant, I talked to last week summed up this phenomena eloquently in a sentence. “You might assume that the soil is too dry for pigweed to germinate; you would be mistaken!” In other cases, burndown or pre applied herbicides were not applied due to a very small window of time to spray because of so many windy days coupled with quick emerging crops.  In a few cases, some of the early emerged Palmer amaranth that was flowering has proven to be difficult to burndown prior to crop emergence.  In a few instances the flowering Palmer amaranth is growing back from even maximum rates of paraquat (pictures right). 

Regardless of the reason, these cotton and soybean fields are behind the eight ball. As I write, there appears to be a front pushing across the river so let’s hope we get a good general rain which should reduce some of these issues on crops yet to emerge.

The question comes in what to do now?  In Roundup Ready cotton the solution some have elected to pursue is try to salvage with Cotoran tankmixed with MSMA over the top. My experience in past years with this plan is that Cotoran/MSMA

tankmixes can provide some control of small ½” tall Palmer but once it reaches 2” or so most will grow back. Others plan to destroy the crop and Palmer amaranth and replant cotton.  This is probably the best option for fields with heavy pigweed pressure that has some size. In Liberty Link cotton the answer is to apply an application of Liberty on the Palmer amaranth even if the cotton is just in the cotyledon stage.  Be aware of the possibility that the Palmer recovering from a burndown application may need a sequential Liberty application to provide good control.

In Liberty Link soybean, a Liberty application as soon as possible will be needed particularly on Palmer regrowing from burndown application.  As mentioned above, be aware of the possibility that the Palmer recovering from a burndown application may need a sequential Liberty application to provide good control.

In Roundup Ready soybean a fomesafen application as soon as possible is warranted.  Hopefully, that will do the job, but be aware that Palmer recovering from a burndown application may not be readily controlled with a fomesafen product or any PPO mode of action herbicide for that matter.  The fact is this Palmer is more mature that the height would suggest as it is regrowing from lateral buds near the soil surface.  Destroying the soybean stand and replanting may be the only viable options in these cases.