October 26, 2001 http://commodities.caes.uga.edu/fieldcrops/cotton/
IN THIS ISSUE:
Crop Situation
Cotton Quality
Late Season Defoliation
Cotton Disease
Management, 2002
Calendar of Events
Crop Situation. (Brown) As of October 25, about 45
percent of the Georgia crop is harvested.
USDA predictions for Georgia have remained at 2.11 million bales from
1.49 million acres, which is an average of 680 lb/A. Perhaps we=ve been biased by the
good crop from this region of the state, but we believe our average yield will
significantly exceed the USDA projection.
Better yields can be attributed primarily to moderate temperatures (we had
very few days in excess of 95o F), reasonable rainfall (except for
an extended drought in August), and light insect pressure (in most areas). Sporadic cool weather in September and
October has slowed the development of late cotton. Last week, many areas had light frost but there was little damage
to bolls. Sub-freezing temperatures
this weekend may end any progress for late maturing cotton, especially if lows
reach 28o F for a couple of hours or more.
Cotton Quality. (Brown) Fiber quality has become a
major issue over the past several years.
Light spot color grades, high micronaire, short staple, and low
uniformity ratio have been costly for Georgia producers. Overall, there are positives in color and
micronaire but negatives with staple and uniformity.
To date, color grades have
been quite good. Better than 90 percent
of our crop is 41 color grade or better.
The primary cause of reduced color grades is weathering. Though we have had significant rains this
fall, fronts have moved through quickly and then skies have cleared, allowing
cotton to dry and brighten. Less than 6
percent is high mic (in excess of 4.9).
High mic is most often associated with drought and high temperatures. These stresses cause boll shed and a
concentration of carbohydrate production in fewer sites, resulting in greater
cellulose deposition per individual fiber and higher micronaire.
Over 30 percent of the
classed samples are short staple.
Similarly, uniformity figures for the Macon Classing Office are 80.7
compared to 82.0 for the Memphis Office.
We hope our numbers will improve as the season progresses. Short staple and low uniformity ratio may be
related to genetics and fruit production zone.
On the latter point, the success of boll weevil eradication allows us to
make bolls in the upper plant canopy, a zone that may have a tendency for
shorter fibers. Short staple creates
problems with spinning and is thus in serious disfavor with mills.
Late Season Defoliation. (Brown) The time has come to GET THE
CROP OUT. Cool temperatures have
arrested boll maturity, so it is questionable how many more top bolls we can
expect to mature. We probably will not
open and fluff many bolls with significant stink bug damage. Most fields will benefit from an aggressive
rate of boll opener (Cotton Quik @ 2 qt/A; ethephon @ 2-2.6 pt/A; or Finish @
1.5 pt/A) and a standard defoliant (DEF/Folex, Ginstar, Harvade, or Aim). The only fields to gamble with and not spray
are those that currently have few open bolls.
There is some chance that a freeze is not imminent and that these fields
may yet survive and progress.
Cotton Disease
Management, 2002: It=s not too early to begin preparations now. (Kemerait) During the 2001 season, most cotton disease problems, such as
seedling disease and Fusarium wilt, have been minor across the state; however,
individual growers have suffered significant yield losses from boll rot and
nematode damage. Substantial boll rot appeared
in some fields where dense growth occurred from excessive nitrogen
fertilization and/or inadequate control of plant height with growth
regulators. Also, an interesting boll
rot, apparently caused by the fungus Colletotrichum, appeared in several
southwest counties earlier in the season.
This rot began with deep, sunken lesions on the boll that produced
copious spores and eventually engulfed the entire fruit (Figure 1). Unlike more common boll rots, where the
pathogen infects after the boll is damaged by insects or as the boll begins to
open, Colletotrichum is able to produce its own wound, known as
anthracnose (NOT related to anthrax--some folks have confused the
two). This boll rot seemed to be
confined to a specific region in the state and was most likely associated with
early season weather patterns, such as tropical storms.
Disease preparations for
2002:
Growers who have had troubles with seedling disease in the past may want to
consider using fungicides in the hopper box or in the furrow at planting next
season. Granular and liquid in-furrow
formulations have been effective at reducing seedling diseases in some
instances in Georgia. Obviously, cooler
and wetter conditions at planting can make seedling disease worse, but this is
most often true if the field has a history of seedling disease. Cool temperatures alone have much less
impact on seedling disease. Growers who
have had a problem with Fusarium wilt this season should consider rotating the
troubled field out of cotton and also providing control of parasitic
nematodes. Successful management of
boll rot next season will depend on the weather and the reduction of rank
vegetative growth.
Nematodes: Damage from parasitic
nematodes has caused problems for growers and researchers across the state this
season. In some cases, growers were
unaware that they had a problem with nematodes until this season; perhaps
because they were finally able to compare Agood cotton@ with Asorry cotton@. Severe
yield losses were observed in fields infested with root knot nematodes,
reniform nematodes, and in several cases, sting nematodes. In most cases, nematode populations have
been able to build in a field due to poor rotation. Figure 2 was taken
by Tommy Cummings in a field in Jefferson County that was severely affected by
root knot nematode. Note that the
plants in the foreground appear to have been killed by the nematodes; in fact
the nematode pressure caused them to Acut-out@ prematurely.
Nematode preparations
for 2002:
Growers who are concerned about nematode populations in their fields should be
collecting soil samples for analysis now.
If they wait until later in the year, the ability of the diagnostic lab
to find nematodes is reduced because 1) eggs that are present are not
identified, and 2) many parasitic nematodes that remain in the soil will travel
to greater depths and will not be included in the sample. If a grower is submitting samples to
diagnose a problem from this season, they are considered Atrouble shooting@ and no charge will be
applied. However, even though a charge
may be applied for other samples, the results will be well worth the
investment. From these results, the
grower will be able to determine IF he has a nematode problem and what types of
nematodes are in the field. Knowing the
type of nematode will help the grower determine suitable winter cover crops and
also rotational crops for the next season.
For example, a cotton grower with root-knot nematode problems would not
want to plant corn or sorghum in rotation with cotton; however a grower whose
fields are infested with reniform nematodes could rotate his fields with either
crop. Growers who have had a problem
with nematodes this season should consider crop rotation or the use of
nematicides for next season. They may
wish to map their fields now in order to know where the Ahot spots@ are for the following
season. The benefits of pulling stalks
in the field at the end of the season for nematode management is not likely to
be worth the cost or effort. Deep
turning the field at the end of the season will also not affect the nematode
populations.
For further information
on disease and nematode control in cotton, please do not hesitate to contact
me.
Calendar of Events:
December 11 & 12, 2001 - Cotton Production Workshop ‑
RDC, Tifton, GA
January 8‑12, 2002 - 2002 Beltwide Cotton Conference ‑
Atlanta, GA
Prepared by:
Steven M. Brown,
Extension Agronomist-Cotton
Bob Kemerait, Extension
Plant Pathologist
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