Arkansas Cotton Update and 2022 Mid-South Cotton Defoliation Guide

by Bill Robertson, Extension Cotton Agronomist, and Tom Barber, Extension Weed Scientist - August 24, 2022

We are quickly approaching the finish line with this cotton crop. The hot dry summer moved cotton toward cutout quickly. Rainfall and a break in temperatures at the end of July and into August have given our crop second wind. This has made the determination of cutout more difficult. Determining cutout and when to start applying harvest aids are important and difficult decisions we must make. Most people in the field will delay pinpointing the date of cutout if the node above white flower values run flat week to week even if the value is below five. This indicates the plant is still putting on new nodes and leaves to help feed the boll load.

We now have very active plants with tremendous potential for regrowth. These plants present a challenge for those in the field evaluating maturity. While leaf abscission and boll opening are an active process tied to senescence, their rates slow greatly when plants are active as this process is hormone driven. Boll maturation continues at a steady pace as it is temperature driven. With very active plants, open boll evaluations will greatly underestimate maturity. The best way to determine boll maturity is to slice bolls.

The 2022 Mid-South Cotton Defoliation Guide goes into more details on the process of defoliation, the timing of applications, application coverage, as well as products. We generally need to implement a two-shot approach in Arkansas. We have seen that the products of choice have shifted in the last couple of years to Finish and Thidiazuron in the first leaf drop application followed by Folex and Ethephon on the boll opening application. We are also noting an increased use of PPO products replacing Folex in the second application regardless of the presence of broadleaf weeds.

The recent rains have triggered a significant increase in weeds coming out of the top of the cotton in 2022. We are seeing grasses and morningglories. An early application of glyphosate prior to the initial harvest aid application is often effective on grasses if grasses are an issue. Glyphosate can also be tankmixed with Finish and Thidiazuron in the first application but may cause increased cotton leaf desiccation due to the surfactant load in the glyphosate. The addition of PPO’s such as ET, Aim, or Sharpen in the second application is generally very effective on morningglories. An increase in the rate of products as directed on the label is often recommended as well as using full recommended crop oil concentrate rates. Coverage is critical. The multilayers of leaves associated with morningglories will often require a third application consisting of spot treating with harsher products. Desiccants containing paraquat are generally very effective in this situation and can be accomplished using an airplane to spot spray fields. Keep in mind, that a desiccant will lock a green boll up if it does not pop when squeezed so do not apply these too early. 

The 2022 crop is likely our most expensive we’ve ever produced. We need a good September to finish maturing this crop and an effective harvest aid program to preserve yield and fiber potentials to achieve the yield and fiber quality we have come to expect the last few years.