Abstract
AbstractSince the release of dicamba-tolerant cotton in 2016, preplant and POST applications of dicamba to control glyphosate-resistant Palmer amaranth have increased. With the increase in area treated with dicamba, the risk of off-target movement to nontarget crops has increased. A field study was conducted at the Texas Tech University New Deal Research Farm equipped with subsurface drip irrigation in 2017 and 2018 to evaluate non-dicamba tolerant cotton response to dicamba when applied at four crop growth stages [first square (FS) + 2 wk, first bloom (FB), FB + 2 wk, and FB + 5 wk]. Dicamba at 0.56 (1×), 0.056 (1/10×), 0.0112 (1/50×), 0.0056 (1/100×), and 0.00112 (1/500×) kg ae ha−1 was applied to ‘FM 1830GLT’ cotton. When applications were made at FS + 2 wk, a shift in boll nodal position was apparent following dicamba at the 1/50× rate in 2017 and at 1/10× in 2018 compared to the nontreated control (NTC). A shift in boll distribution from the 1/50× rate of dicamba was apparent at FB in 2017, but not in 2018. Dicamba applied at the 1× rate at FB + 2 wk resulted in reduced boll numbers. No change in boll number or boll position was apparent following any dicamba rate when applied at FB + 5 wk in both years. Dicamba applied at 1/500×, 1/100×, and 1/50× rates at all timings did not affect yield relative to the NTC. When dicamba was applied at the 1/10× rate, the greatest yield loss was observed at FS + 2 wk followed by FB and FB + 2 wk. Micronaire increased following dicamba applied at 1/10× at FS + 2 wk, FB, and FB + 2 wk in 2017. In 2018, micronaire decreased following dicamba applied at 1/10× at FB + 5 wk.
Highlights
Upland cotton is grown on 5.7 million hectares in the United States with approximately 40% grown in Texas (USDA-NASS 2018)
First Square þ 2 Wk At the first square (FS) þ 2 wk application timing, the 1× rate of dicamba resulted in complete boll loss in 2017 and 2018 (Figure 1)
The 1/10× rate resulted in a substantial boll reduction between nodes 5 and 14 relative to the nontreated control (NTC)
Summary
Upland cotton is grown on 5.7 million hectares in the United States with approximately 40% grown in Texas (USDA-NASS 2018). Little information exists on the effects dicamba has on cotton physiology; namely, boll production and reduction following applications of labeled and sub-labeled rates of dicamba at different growth stages. Fiber quality as affected by dicamba were not reported in the previous trials following the different rates of synthetic auxin herbicides at different growth stages.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
