Effects of 2,4-D choline on fruiting in sensitive cotton

With the increase in hectares planted to auxin-resistant cotton, the number of preplant, at-plant, and post plant applications of dicamba and 2,4-D choline to aid in the control of troublesome broadleaf weeds including glyphosate-resistant Palmer amaranth has increased. More dicamba and 2,4-D choline applications means an increased risk of off-target movement. Field studies were conducted in 2019-2021 at the Texas Tech University New Deal Research Farm to evaluate dicamba-resistant cotton response to various rates of 2,4-D choline when applied at four growth stages [first square (FS) + 2 weeks (wk), first bloom (FB), FB + 2 wk, and FB + 4 wk]. Applications of 2,4-D choline were applied at 1060 (1x), 106 (1/10x), 21 (1/50x), 10.6 (1/100x), 2.1 (1/500x), and 1.06 (1/1000x) g ae ha-1 to Deltapine 1822 XF cotton. Relative to the non-treated control, yield losses were observed in all years at FS + 2 wk and FB from rates of 2,4-D choline ≥ 1/100x. At the FB + 4 wk application, only the 1x rate of 2,4-D choline resulted in a yield reduction in all three years. Micronaire, fiber length, and uniformity were negatively influenced by the 1/10X and 1X rates of 2,4-D choline at various timings in 2019, 2020, and 2021. In addition, short fiber content, neps, and seed coat neps increased where micronaire, fiber length, and uniformity were negatively impacted.