Due to the devolopment of glyphosate resitant weeds in our area, growers are using herbicides that haven’t seen much use of late. I found a useful document from Australia that shows herbicide damage on cotton. This and the MU troubleshooting guide will help you to discover the cause of your problem.
For example, this week we were in a bean field that was primarily brown, unhappy looking Liberty Link beans. The damage was uniform throughout the field, but as you can see in the second photo of the same plant, not on the younger growth (for most plants). We are still in process with figuring out what happened in this field, but what I want to communicate is:
2) the pigweed next to the beans will probably not survive.
3) the uniform pattern throughout the field (but not on vegetation in field margins) suggests the damage was part of the grower’s weed control program. It appears that some amount of crop damage will be part of weed control programs until new technology arises.