Cotton -- The University of Georgia


July 27, 2001                                                    


Crop Condition

Manage Stink Bugs

Black Rot Revisited and Updated: What’s left for young agronomists and pathologists

Cotton Producers Can Expect Sizable POP This Fall


Crop Condition.  (Brown) Prospects for the 1.6 million-acre 2001 Georgia cotton crop are significantly better than that of previous seasons.  Rains in June through early July brought good vegetative growth and a respectable push into bloom.  Many parts of the state went without rain

from the 4th of July until this current week.  Crop growth stage ranges from a few acres in the early square stage to substantial acreage just past peak bloom approaching cutout.  Scattered acres have been abandoned because of severe, persisting drought.  Water is critical to carry the fruit load to maturity.


Georgia Agricultural Statistics estimates that as of July 23, 65 percent of the crop is setting bolls.  Crop conditions on that date were 1 percent–Very Poor, 7 percent–Poor, 29 percent–Fair, 49 percent–Good, and 14 percent–Excellent.


Over the past weeks we’ve seen numerous fields with poor color.  Pale, yellow foliage has been attributed to 1) tardy N sidedress applications,  2) N leaching and/or waterlogged roots caused by excess rain, 3) inadequate K rates,  4) imbalances between N and S.  There are a few situations in which it is hard to explain what happened, why the field has yellowed.


Now is also the crucial period for insect control.  Scouts and growers should sharpen their efforts on stink bugs and corn earworms.  When needed, timely intervention could return 50 to 200 lbs of lint for a treatment that costs less than $10/A.


Manage Stink Bugs.  (Roberts)  Stink bugs are a primary pest of Georgia cotton and must be effectively  managed to maximize profit.  Management may not mean spraying every field for stink bugs, but it does mean scouting each field and using insecticides when needed.  Scouting for stink bugs should be initiated when cotton begins setting bolls.  Populations may be estimated using an internal boll damage assessment (the preferred method) and/or a drop cloth count.  Fields which have not been treated with a broad spectrum insecticide such as a pyrethroid during the past two weeks are at highest risk for stink bug damage.  To date, a large percentage of fields in Georgia are in this category.


Stink bugs damage cotton with their piercing/sucking mouthparts by injecting digestive enzymes and feeding on developing seeds within bolls.  In addition to physical damage to bolls, this process allows the entry of rot organisms that also reduce yield and quality.  Bolls which have been damaged by stink bugs are easily recognized by looking for internal symptoms of injury.  Internal symptoms include stained lint and/or warty callous growths on the inner surface of the boll wall.  Previous research has shown that these callous growths appear within 48 hours after the bug feeds on a boll.  In addition to stink bugs, other bugs such as tarnished plant bug and leaf-footed bugs may also feed on developing bolls and cause damage which is indistinguishable from that caused by stink bugs.


During 1999 and 2000, Drs. Gary Herzog and Jeremy Greene coordinated research addressing economic thresholds for stink bugs.  Five trials were conducted in Bt cotton fields.  Treatments included Bidrin (8 ozs/A) sprays at various threshold levels (10, 20, and 30 percent internal boll damage, 1 stink bug per 6 row feet, and an untreated).  Plots were scouted weekly and each treatment was treated on an as needed basis.  Highest yields (+109 lbs lint/A) were obtained in the 20 percent internal damage threshold plots which required two applications of Bidrin.  Similar yields were also produced using the 10 percent damage threshold but with the expense of two additional Bidrin Sprays.  The 30 percent damage threshold and 1 stink bug per 6 row feet treatments required one or fewer Bidrin sprays and did not result in significant yield increases compared with the untreated.  Because plants were exceedingly tall at several sites, bugs were difficult to detect in the elevated canopies using the drop cloth technique.  This could have resulted in densities exceeding threshold without detection, fewer insecticide applications, more boll damage, and reduced yields.  Based on these studies, managing stink bugs using the 20 percent internal boll damage threshold returned a net gain of $48.48 to the grower.  Net gain was calculated with yield gain at $0.60 per lb of lint minus $8.31 per Bidrin acre application ($5.31 for insecticide plus $3.00 application costs).  Two on farm trials were also conducted in Irwin County.  Treatments included a pyrethroid at the 20 percent internal damage threshold and an untreated.  One application was needed at each location and yields were increased 122 and 56 lbs lint/A when stink bugs were managed.


Recommended insecticides for stink bugs include several pyrethroids and the organophosphates Bidrin and methyl parathion.  Vydate was also recently labeled for control of green and southern green stink bugs.  Based on additional research by Drs. Herzog and Greene, bolls are most susceptible to stink bug injury until 20 to 25 days after white bloom.


Black Rot Revisited and Updated: What’s left for young agronomists and pathologists? (Kemerait, Jost, Harris, and Gary Gascho)   It has been about five years since a malady of cotton, later to become known as “black root”, was recognized and initially studied in Georgia by Dr. Rich Baird and county agents such as Forrest Connelly and James Clark.  Black root was described as a new “disease”, although the causal agent was unknown.  The condition was reported to be widespread in 30 counties in the state.  As many are aware, symptoms of black root included a superficial darkening of the roots, gall formations that could be cracked and/or corky in texture, severe boll abortion, and foliage with symptoms that have been referred to as “windowpaning” and like chemical injury.  Since that time, and after great effort by Dr. Baird, no pathogen has ever been successfully linked to black root and the malady is now considered to be most likely the result of environmental conditions.


The recent studies of black root have been conducted by Dr. Gary Gascho, a soil scientist located in Tifton.  It is now generally recognized that most true cases of black root are confined to poorly drained flatwood soils, especially in areas such as Appling, Jeff Davis, and Berrien Counties.  However, at least some black root is also appearing in other poorly drained sites, such as in Cook County.  It now seems that the earlier description of black root as “widespread in 30 counties” was premature.  There has not been a confirmed case from well-drained, coastal plain soils, though the general symptoms of black root make it easy to confuse black root with other stress related problems of cotton.  For example, plant samples have been submitted in the past year from Houston and Bleckley Counties with some symptoms that resembled black root, but turned out to be unrelated.


Dr. Gascho’s work has focused on chloride toxicity as a possible cause of the black root problem.  A similar problem and damage occurs in certain susceptible cultivars of soybean that translocate chloride ions from the roots to the foliage.  (Non-susceptible soybean cultivars retain chloride in their roots.)  In his research, Dr. Gascho has been able to produce similar symptoms on cotton grown in the greenhouse in the presence of high chloride levels.  He has also conducted field research to determine if soil amendments such as poultry litter, gypsum, or low chlorine fertilizers might help to reduce the severity of the problem.  Poultry litter, which is an organic source of nitrogen, seems to be a partially effective means to minimize the severity of black root in fields where it is a problem.  Poultry litter contains many nutrients and non-nutrients, which makes the reason for the positive growth, development, and yield responses in cotton difficult to discern.  The current thought is that black root of cotton may be the result of interactions between chloride and nitrogen that occur in poorly drained fields and that the dark symptoms on the root may actually be from ammonia burn.  As of now, the idea of the ammonia burn is unproven; however, observations by Dr. Gascho in 2001 have implicated nitrogen nutrition as a factor.


Because of the symptoms and yield losses associated with black root, plant pathologists and agronomists will continue to play a role in the study of black root, both evaluating it in the field and diagnosing it in the disease clinic.  Although no pathogen has ever been successfully linked to this condition, the ultimate cause of black root remains elusive.  Therefore, pathologists will remain involved in the study of this condition and contribute expertise that will lead to a better understanding of the issue.


Cotton Producers Can Expect Sizable POP This Fall.  (Shurley)  The 2001 US crop is likely to be 19 to 20 million bales.  USDA’s July forecast was 19.2 million bales.  While there are many unknowns, it will be difficult to pull out of the current weakness in the market.  One factor that producers have relied on in recent years to augment low cash prices has been the Loan Deficiency Payment (LDP) or POP.


The POP is derived from the A-Index or “world price” of cotton as shown in the table below.  When the A-Index goes down, the AWP declines and producers will be eligible for a POP payment if the AWP is less than the loan rate.


This past year, the A-Index was strong during harvest time and the POP reached a maximum of about 4 cents.  After harvest, the “A” begin to decline as did US prices as world production was larger than expected and demand began to slip.  This resulted in producers getting a large marketing loan gain if cotton was stored in CCC loan or a POP of 15-20 cents or more if producers declined the POP at harvest and held the cotton in regular storage.


One thing that has happened in the past 2 years is that the A-NY relationship has gone from what typically was a minus 3 to 5 cents to a plus 3 cents or more.  This is because US cotton prices have weakened more relative to foreign prices.  The result is that even though US prices are low, we’re not likely to get as much POP to help us out as we have in the past.



Example of US and World Price Relationship and Calculation of POP Payment



Futures and Cash


A-Index - NY Relationship




Futures (Dec) 7/25/01



A-Index 7/26/01


Basis 7/25/01





Current Cash Position








POP (51.92-AWP)


Total Price







With world production and stocks increasing, the A-Index is currently at about 44 cents and may go even lower.  Currently, if the “A” stays were it is, we’re looking at a 21 cent POP this fall.  With futures prices in the low 40's, this translates into something in the upper 30's for a cash market.  So, if the A-NY relationship stays the same as it is now, producers are looking at a total of around 60 cents this fall one way or the other.


It is likely this year will be the opposite of last.  The “A” will probably increase over the winter months.  This means, the temptation will be to take the large POP this fall.  Then, the MAJOR decision becomes what to do with the cotton.  According to the latest data, only 4% of the Georgia crop and 5% US is contracted.  Profitable opportunities have been almost non-existent. 



Estimated Acreage Equivalent of Cotton Forward Contracted as of July 1



2000 Crop

2001 Crop











Source: USDA-AMS


The alternatives available include POP and sell, POP and store, POP and place “on-call” or price later, POP and sell plus Call Option, or place in Loan.  At 21 cents per pound, the $75,000 limit on LDP’s (POP’s) and marketing loan gains will be reached at approximately 715 bales.


With cotton prices so low, it is natural for producers to consider spending as little as possible or nothing on late season inputs.  Every input should always be evaluated in good years as well as bad.  But cost savings must be weighed against potential yield and quality losses and remember to base this decision on 58 to 60-cent cotton and not 40.


Prepared by:

Cotton -- The University of Georgia

Steven M. Brown, Extension Agronomist-Cotton

Philip H. Jost, Extension Agronomist-Cotton & Ag Crops

Glendon H. Harris, Jr.,  Extension Agronomist-Soils & Fertilizer

Bob Kemerait, Extension Plant Pathologist

Phillip Roberts, Extension Entomologist-Cotton

Don Shurley, Extension Economist

Gary Gascho, Research Agronomist


Tiftarea UGA Cotton Research Tour

Wednesday, August 15, 2001


9:00     Convene at the RDC Pavilion


9:15     Depart for RDC Pivot

            Narrow Row versus Wide Row (Bader)

            Foliar Fertilizer / Hormone Products (Harris, Bednarz)

            Skip Row Patterns (Jost, Brown)

            Effects of Extreme Plant Bug Populations (Roberts, Bednarz)

            Thrips Control with Seed Treatments and In-Furrow Products (Roberts)


10:00   Depart for Gibbs Farm

            Enhanced Glyphosate Tolerance Events (May)

            Official Variety Trial (May)

            Breeding Nursery (May)

            Nematode Control (Davis, Bader)

            Irrigation Studies (Bednarz)

            N Studies (Gascho)


12:15   Depart for Ponder Farm

            Lunch (provided on site)

            Population Densities (Bednarz)

            Flowering Habits of Early versus Full Season Varieties (Bednarz)

            Weed Control with Enhanced Glyphosate and Liberty Cotton (May)

            Cadre Carryover (Bednarz, Prostko)

            Messenger (Bednarz, Brown)

            Growth Regulation in Narrow Row Cotton (Bader)

            Weed Management


2:45     Depart for Lang Farm

            Nematode Control (May, Davis)

            Thrips Control / Planting Date (Roberts)

            Residual Litter Rates (Gascho)

            Transgenic Cotton / Technology Systems Trial (May)

            Conservation Tillage / Rotation (Lee)


3:30     Return to RDC


The tour is intended for growers, county agents, and agribusiness persons.  Participants are encouraged to gather in as few vehicles as possible to expedite travel from site to site.  Total number will be limited to the first 150.  For registration, please contact the RDC Conference Office at 229 / 386-3416 no later than Friday, August 10.