Defoliating Cotton to Create Florida’s Snowy Fields

Oct 04, 2021

By Ethan Carter and David Wright

It’s that time of year again, cotton defoliation is hot on the heels of peanut harvest. Many farmers are in the middle of digging peanuts, and are starting to pick peanuts, while also setting their sites on cotton defoliation. From first bloom to open boll is typically about 60 days, and harvest generally occurs 25-30 days later. Often, growers wait too late to defoliate, as the field is ready earlier than typically expected. There are two primary techniques used to effectively gauge field readiness when it comes to defoliation. When a cotton field has reached either of the thresholds listed below, it is time to defoliate the field.

Plants have 60-70% open bolls

Plants have 4 or fewer nodes above the highest cracked boll (NACB)

A sharp knife is a less scientific but a tried and true way to determine the maturity of individual bolls. Mature bolls are difficult to cut, have brown seed coats, and fibers that will string when you attempt to cut. If you can cut through the boll with a knife it is not mature. Using this technique to evaluate boll maturity can have value for tracking the progression of the crop, but the final defoliation decision should be made based on on of the two criteria listed above.

There are several active ingredients that can be effectively used as harvest aids for cotton. The different Active Ingredients (AI) all have varying strengths and weaknesses in relation to the individual aspects of effective defoliation. As such, two or more active ingredients are frequently used together. For example Ethephon, Thidiazuron, and Tribufos (Prep, Dropp, and Folex) are commonly all used together. Table 1. outlines the efficacy of several active ingredients for specific aspects of defoliation.

defoliating-cotton-to-create-floridas-snowy-fields

Table 1. Performance rating of harvest aids by function (P=poor, F=fair, G=good, E=excellent
Adapted from: https://edis.ifas.ufl.edu/pdf/AG/AG18800.pdf

Brand names associated with the active ingredients shown in Table 1. are listed below:

PPO Inhibiting Herbicides

Aim (carfentrazon)
ET- (Pyrafluefen ethyl)
Resource (flumiclorac)
Blizzard (flutiacet-methyl)

Tribufos

Def 6 Emulsifiable
Folex 6 EC

Thidiazuron

Daze 4SC
Frefall SC
Klean-Pik 500 SC
Takedown

Thidiazuron + Diuron

Ginstar
Adios
Cutout
Redi-Pick

Ethephon

Prep
Boll Buster
Super Boll,
SetUp 6 SL,
many others

Ethephon + Cyclanilide

Finish 6 Pro

Ethephon + Urea Sulfate

FirstPick

Temperature plays an important role in defoliation and can drastically impact the fields defoliation time. During cooler weather, it is necessary to increase defoliant rates, and it is not uncommon for a 10–15-day window from date of defoliation to picking. Read the publication 2020 Cotton Defoliation and Harvest Aid Guide for specific product and rate recommendations based on temperatures at the time of defoliation.

General Notes about Cotton Defoliation

Growers should be weary of using Paraquat, as plant leaves tend to stick/hang on to the plant which results in trash in the lint during picking.
Waiting for frost to kill plants prior to harvest is not a good idea, once frosted, any unopened bolls will not open.
High fertility fields are often the hardest to defoliate; this should be considered when selecting products and rates.
Fields with dense canopies and high numbers of green bolls may require two harvest aid applications, with the first focused on defoliation and the second on boll opening.
The rainfree periods for harvest aids vary greatly. If rain is in the forecast, be sure to be sure to consider the rainfree period of all products used, as illustrated in the table below.

defoliating-cotton-to-create-floridas-snowy-fields

Specific product options and rates are included in the UGA Pest Management Handbook, or by using the following link:

UGA Cotton Defoliation Guide

Source : ufl.edu

Video: Can Gene Editing Give Seeds a Stronger Start?

Reagan Reed has a way of describing his research that might make a plant breeder pause.

“I’m the sort of person who likes to break things to understand them,” he says.

What he breaks are genes involved in seed germination. Reed, a Ph.D. candidate at the University of California, Davis, is investigating whether changing those genes can help seeds establish healthy plants under a wider range of conditions.

Reed recently attended the National Association for Plant Breeding meeting in College Station, Texas, as an NAPB Borlaug Scholar. His work speaks to a question that matters well beyond a research lab: what does it take for a seed to get a crop off to a strong start?

A seed that germinates quickly, alongside the others planted with it, spends less time vulnerable to stresses before seedlings become established.

“If you’re able to bridge that gap between germination to stand establishment, then that’s going to give you the highest probability of having a solid yield that year,” Reed says. “There’s a bunch that can go wrong after that, but it maximises your yield from the start, at least.”

Reed works in Dr. Imtiyaz Khanday’s lab at UC Davis, where his research focuses on seed quality in tomatoes and potatoes. He brings an unusual academic background to the work: at Skidmore College, he studied both biology and Latin.

Reed believes that combination prepared him for research. Translating an ancient text means studying each word, weighing its possible meanings and using context to reach the best interpretation. There is rarely a way to know with complete certainty what an author intended. Science, he says, requires a similar willingness to work through uncertainty.

“Attention to detail and comfortability working with uncertainty,” is how he sums up what Latin taught him.

In the lab, uncertainty can produce a surprise. Reed describes changing one gene and seeing little effect. Changing a second gene also appears to do little. Put both changes in the same genetic background, though, and the result can be substantial.

“I break this gene, nothing really happens. I break this other gene, nothing really happens. I combine them into the same genetic background, and now there’s a massive effect,” he says.

Those interactions matter as researchers gain the ability to edit multiple genes at once. They also complicate any simple account of how a trait works: improving a seed may depend on understanding what several genes do together.

For Reed, the question is whether that knowledge could help seeds germinate reliably when conditions are difficult. Some of the genes he studies prevent germination under certain conditions. That response may serve a plant well in one setting while limiting its usefulness in agriculture. He wants to learn what happens when those genes are changed, and whether the result improves establishment.

Yet a discovery that works in a lab still has a long way to travel before it reaches a field. Reed argues that agricultural biotechnology faces an economic challenge as well as a scientific one. New tools can create value for farmers, he says, but developing them requires a way to support the work in an industry where margins can be thin.

His fellowship with Flagship Pioneering gave him a view across AI, agriculture-related work and human health research. It also reinforced the importance of bringing people with different expertise into the same conversation—a benefit of gatherings such as the NAPB meeting.

“You need to have a team of people with different backgrounds who are willing to work together and approach the same problem in different perspectives and different ways,” he says.

That thinking connects the different parts of Reed’s path. Latin taught him to examine details without expecting a perfect answer. Gene editing lets him test what individual genes do—and what happens when their effects combine. Working with people beyond his own field helps him ask what those findings could become.

He came to agriculture because of its reach: the possibility that work by a small group of researchers could eventually make a difference on a much larger scale. His immediate focus is smaller and more precise. He wants to understand what helps a seed get through its first days and become a healthy plant.