On August 21 a defoliation demonstration was sprayed at the entrance to the West TN Research and Education Center in Jackson. It is on the east side of the main drive about half way to the main building. Signs will be posted if you have interest in looking at the treatments. Cotton ranging from just reaching cutout to having nearly 100% open bolls is complicating defoliation decisions. Below are several scenairos to consider:
DROUGHT STRESSED COTTON: Cotton that has been drought stressed where little or no rain has fallen all summer and applied nitrogen has not been utilized makes for difficult decisions. Most of this cotton has 500 pound potential at best and producers are not wanting to spend much money to defoliate. APPROACH A.)If you are in this situation using a Folex based program is advisible. If your field requires boll opening the addition of 16-24 oz of ethephon is encouraged. This approach will work well if you have enough picker capacity to keep up with the spryer and it does not rain. Currently there is a tropical storm headed toward the Gulf of Mexico and if rain falls after you make ths application re-growth with occur quickly and fields will require a second defoliation. Aim, Display or ET can be substituted for Folex in this system. APPROACH B.) Utilization of Freefall (thidazuron) for re-growth prevention along with Folex and ethephon is advisible if rain is expected within 10 days of harvest aid application. Freefall needs to be appied at least at the 1 gallon to 80 acres rate (preferably 1 gallon to 60 acres) to help slow re-growth. Additionally, if you are growing a Liberty Link variety (ST 414LLB2, ST 5445LLB2, FM 1773LLB2) you can add a glyphosate product to the mix to help aid in re-growth control. Glyphosate will need to be applied at a minimum 1 pint per acre to get adequate re-growth control. Glyphosate in this case is an addative to the Folex-ethephon tank-mix, it will not provide leaf drop or boll opening.
Well Cutout Cotton With Good Yield Potential: This is the typical scenaior most are familar with. If cotton in this scenaio is greater than 44 inches tall, or has a dense canopy I recommend a the two pass system listed below. SINGLE PASS SYSTEM A single pass attempt can not cut corners and needs to be thidazuron based. The thidazuron component for re-growth control can come from Freefall or Ginstar (use Freefall if you plan to plant wheat following cotton harvest). Use at least 1.6 oz/ac of thidazuron to supress re-growth and aid in leaf drop. The herbicidal component can be Folex, Aim, Display, or ET based on the economics of the products. Since you are including thidazuron, do not get your herbicidal component rate too high to avoid ‘stuck’ leaves. Finally, choose either Finish 6 Pro or ethephon at 24-32 oz to provide boll opening. TWO PASS SYSTEM The first application should serve to ‘set the crop up’ for the secoond pass. Similar to the single pass system thidazuron at 1.6-2.0 oz per acre plus a low rate of Folex tank-mixed with 8-12 oz of Finish or ethephon will serve to open the canopy to allow air to circulate and provide better canopy penetration of products in the second pass. I generally recommend Aim or ET as the herbicidal component in the second pass since they are excellent at removing juvenile growth that the first pass missed or any re-growth that may have occurred. Adding 24-32 oz of ethephon with aid in boll opening. The second pass should be made between 7-10 days after the first application based on speed of activity and temperatures.
IRRIGATED AND RANK COTTON: In this scenairo a TWO PASS SYTEM IS RECOMMENDED! Start with a similar approach from above in a two pass system. Folex (4 oz), Freefall (2.0 oz), and Finish 6 Pro (10 oz) or ethephon (12 oz) is a good start. You can substitute Ginstar (3.0-4.0 oz) if you are not planning to plant wheat after the cotton is harvested. The second pass needs to contain Aim (0.75 oz), or ET (1.5 oz) plus ethephon at 24-32 oz. Allow adequate leaf drop to occurr prior to making the second application. This will facilitate penetration of defoliants into the canopy for better results.
Finally, remember that as temperatures drop application rates of Folex, Finish, Ginstar and ethephon need to increase to maintain good activity. The cotton in the picture below was defoliated 7 days ago with ET (1.5 oz), Freefall (2.0 oz) and ethephon (32 oz) on the Experiment Station in Jackson.
