The Effect of Cotton Growth Stage on Susceptibility and Fruiting Patterns Following Exposure to a Sub-Lethal Rate of 2,4-D

As Xtend and Enlist technologies become commercially available in an effort to combat herbicide-resistant weed species, the synthetic auxin herbicides 2,4-D and dicamba will be used on many more acres. While these herbicides hold great promise in controlling weeds that have become resistant to other herbicides such as glyphosate, they come with some inherent risks. The primary risk associated with their use is the potential for off-target exposure to susceptible species, such as cotton. Off-target exposure can manifest in many ways, but the primary vectors of concern are herbicide spray-tank contamination, herbicide drift and deposition, and herbicide volatility. All of these concerns remain valid even when exposure is to only a sub-lethal concentration of the auxin herbicide. Thus, the effect of a sub-lethal concentration of 2,4-D on the growth and fruiting pattern of susceptible cotton was analyzed as a function of growth stage at the time of exposure. The experiment was conducted in Starkville and Brooksville, Mississippi in 2014, 2015, and 2016.