After nearly two decades of battling glyphosate-resistant Palmer amaranth, we all clearly understand dozens of reasons why we must aggressively control this weed. However, there may be an additional reason that you probably are not aware of until now.
Cooperative research led by Taylor Randell, our graduate student, has determined this pesky weed not only competes with the crop but also attracts tarnished plant bugs into the field which then feed on cotton plants. Research from 2017 and 2018 noted 9 to 15% damaged cotton terminals from plant bugs in plots maintained free of Palmer amaranth.
In the same study when Palmer amaranth was allowed to remain in the plot for up to 35 days before removal (“weedy”), damaged cotton terminals ranged from 25 to 39%. Cotton terminal damage from plant bugs influenced by Palmer amaranth caused yield loss at the Macon county site in one of two years.
Conclusion: This exciting research just adds more science behind our decade-long recommendations for managing Palmer amaranth, which include the following: No Palmer up at planting, two effective at-plant residual herbicides used at rates that will not hurt the cotton crop, timely post applications, and finishing the season by improving late-season weed coverage and control, while reducing cotton injury, by applying conventional chemistry through your layby rig or hooded sprayer.