The Effect of Cotton (Gossypium hirsutum L.) Growth Stage on Injury and Yield When Subjected to a Sub-Lethal Concentration of Dicamba

2,4-D (2,4-Dichlorophenoxyacetic acid) and dicamba (3,6-Dichloro-2-methoxybenzoic acid) are two of agriculture’s oldest modern herbicides. As the continued development of herbicide-resistant weeds poses an increasing challenge to producers, new biotechnology will rely more heavily upon these auxin herbicides in weed control systems of the major row crops. Cotton (Gossypium hirsutum L.) remains an important agronomic crop in the southern United States and has the potential to be produced on more acres in the near future. Cotton production systems utilizing conventional or non-auxin-tolerant cultivars will be at in increased risk of exposure to off-target applications of the auxin herbicides in the coming years. Due to the inherent nature of the auxin herbicides, these off-target applications may manifest primarily as tank contamination or herbicide drift events, and may occur at different timings that correlate with varying cotton growth stages. A study was conducted to determine the effect of cotton growth stage on susceptibility to injury and yield effects from off-target sub-lethal concentrations of the auxin herbicides 2,4-D and dicamba. Data metrics analyzed included visual crop injury, crop height, relative crop maturity, and differential crop yield characteristics. For the sake of brevity and time constraints, only dicamba results will be presented.