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Agronomy notes
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066352/00082
 Material Information
Title: Agronomy notes
Uniform Title: Agronomy notes (Gainesville, Fl.)
Physical Description: v. : ill. ; 28 cm.
Language: English
Creator: Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Place of Publication: Gainesville
Creation Date: November 2006
Subjects / Keywords: Crops and soils -- Florida   ( lcsh )
Crop yields -- Florida   ( lcsh )
Agriculture -- Florida   ( lcsh )
Agronomy -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
periodical   ( marcgt )
serial   ( sobekcm )
Statement of Responsibility: Florida Cooperative Extension Service, University of Florida, Institute of Food and Agricultural Sciences.
General Note: Description based on: January 1971; title from caption.
 Record Information
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000956365
notis - AER9014
System ID: UF00066352:00082


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Vol. 30:11 November 2006

November 6th: Sugarcane Field Day Quincy, FL


C orn Su p p lies ...................................................... .................. 2

Cotton Harvest ...................................... .............................. ........... 2

Glyphosate Resistance is Growing ....................... ........ ................................... 2
How Herbicides W ork 2,4-DB ....................... ........ ..................................... 2
New Herbicide Resistant Cotton on the Horizon................... ............. .................... 3
W ild R adish ............................................. ................ ........... .... 3

Soybean R ust Im pacts in the U .S ........................................................................ .... 4
C over C rops ............... ....... ...... ........... .................. .. ..................... 4
Restricted Use Pesticide Applicator CEU Program On-Line ....................................... 4
W heat V varieties for 2006/2007......................................... ...................................... 5

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Employment Opportunity _Affirmative Action Employer authorized to
provide research, educational information and other services only to individuals and institutions that function without regard to race, color,
sex, age, handicap or national origin. For information on obtaining other extension publications, contact your county Cooperative Extension
Office. Florida Cooperative Extension Service/ Institute of Food and Agricultural Sciences/ University of Florida/ Larry Arrington, Dean.

Corn Supplies

It is expected that corn stockpiles will be
depleted in the U.S. by 2008 due to the high
amount being used in ethanol production.
With ethanol plants that are coming on line,
almost 20% of the 2006 corn crop will be
used for ethanol production and this number
is expected to rise to 30% of the 2007 crop.
Since Florida has not produced large
acreages of corn since the late 1970's, we
will either need to produce more corn or
expect to pay higher prices to import it from
the Midwest. It is expected that corn
acreage will need to increase close to 10%
over the next few years to meet the feed and
biofuels demands for corn even though the
crop will be the third largest on record.
High oil prices will continue to drive the
U.S. to a more "green" fuel that is produced
from agricultural products and corn is the
main ingredient with other crops like
soybean not far behind.

David Wright

Cotton Harvest

Cotton should be harvested as quickly as
possible after opening to maintain yield and
quality. Cotton opening in November
seldom contributes much to final yield since
these late opening bolls were set too late in
the season. Seldom is there a reason to wait
after the first of November to defoliate
cotton in Florida. Days are very short and
very little picking weather is available after
November 15.

David Wright

Glyphosate Resistance is Growing

For many years we believed that glyphosate
resistance would not, or could not, occur.

More crop acreage was grown with
Roundup Ready technology and weed
control was better and easier than ever
before. However, in 2000 horseweed was
found in Delaware that was resistant to
glyphosate. By 2001 it was found in 3
additional states and now a total of 14 states
have confirmed glyphosate resistant

Since the first glyphosate-resistant
horseweed was found, it seems as if the
flood-gates were opened and the number
glyphosate-resistant weeds are growing.
Glyphosate resistance to date includes 11
species world wide with 6 confirmed in
USA and 2 others expected, but not
confirmed. Those of significance to Florida
are Palmer amaranth (Palmer pigweed),
common ragweed, cocklebur*, and common

Glyphosate resistance has been found in
Georgia, North and South Carolina, and
Virginia. Since our production practices are
similar to the states mentioned above, it is
very possible that glyphosate resistance will
also visit Florida. Therefore, it is imperative
that we implement strategies that will reduce
their development. The most beneficial
practices include using herbicides with
differing modes-of-action and implementing
proper crop rotation. These factors alone
will dramatically reduce the occurrence of
herbicide resistance. In short, it is much
easier to avoid the development of resistance
than it is to manage weeds that are resistant.

*suspected of resistance, but not confirmed.

Jason Ferrell

How Herbicides Work 2,4-DB

The herbicide 2,4-DB has been used for
several decades for broadleaf control in

selected legume crops. Two popular
commercial trade names for 2,4-DB include
Buytrac and Butoxone, but several others
are registered.

2,4-DB is classified as a growth regulating
herbicide. It is applied postemergence, over
the top of weeds and desirable vegetation
where it is active on a wide range of annual
broadleaf species. This herbicide is widely
used in forage crops such as alfalfa, clover,
and bird's foot trefoil. It is also used for
broadleaf weed control in several legume
crops including peanuts and soybeans. 2,4-
DB is readily absorbed through the foliage
and diffuses into leaf cells where it then
moves throughout the entire plant.

Since 2,4-DB and 2,4-D are so closely
related, how do legume plants tolerate
applications of 2,4-DB but not 2,4-D? The
answer lies in metabolism. When 2,4-DB
enters into a susceptible plant, the herbicide
is immediately converted to 2,4-D through a
process called beta-oxidation. Once the 2,4-
D has been formed, it imparts the herbicidal
activity. However, legume plants lack the
ability to convert 2,4-DB to 2,4-D through
beta-oxidation, so the compound remains
2,4-DB, which does not possess herbicide

Like other growth regulator herbicides, we
do not know exactly how 2,4-DB affects
plants. However, we do know that 2,4-DB
causes uncontrolled growth, resulting in
twisting of stems, curling of leaves and
sometimes split stems. Some theorize that
this herbicide acts like (mimics) the growth
regulator auxin, but in such a way that the
plant grows itself to death. Other
researchers suggest that the cell walls
loosen, allowing the cells to elongate and
expand. Further work in this area has also

shown excess RNA and DNA biosynthesis,
leading to the thought that this stimulates
excess cell division.

In either theory, the bottom line is that some
cells of the plant growth more rapidly than
others. This results in cells that grow
unevenly, with some cells/tissues getting
crushed and destroyed in the process. The
vascular system is disrupted, blocking water
flow and sugar movement; ultimately
leading to plant starvation and death.

2,4-DB has little to no soil activity and does
not persist in the environment.

Greg MacDonald

New Herbicide Resistant Cotton on the

Due to the development of glyphosate
resistant weeds in the cotton belt, Monsanto
is moving forward with dicamba-resistant
cotton. This technology is several years
away from release, but it will likely give
highly effective and reliable control to
glyphosate-resistant weeds such as Palmer
pigweed, cocklebur, ragweed and
horseweed. This technology is expected be
coupled with BollGuard and Roundup

Jason Ferrell

Wild Radish

With cooler temperatures approaching, it is
time to start thinking about wild radish
control. Wild radish seed germinates when
soil temperatures reach approximately 65
degrees and form a rosette on the soil
surface (Figure 1). At this stage, 2,4-D is
highly effective at rates as low as 1 pt/A.

Waiting to spray until yellow flowers appear
make control much more difficult, require
higher herbicides rates, and injury to winter
forages (ryegrass, oats, etc) is much more
likely. So start scouting fields every few
weeks over the next month and be ready to
spray for wild radish. Early intervention
will provide better control, require less
herbicide, lead to less injury, and allow
more winter grazing.

Jason Ferrell
Figure 1. Wild radish in the rosette growth

Soybean Rust Impacts in the U.S.

Soybean rust did not have a major impact on
the soybean growing regions of the U.S. in
2006. However, it was found for the first
time in October in the Corn Belt states and
will become more of a problem in the future.
Florida had 26 sentinel plots located from
south Florida to Pensacola this year. Many
of these plots became infected with soybean
rust, but did not increase in severity due to
the drought that was experienced from
February through July. Spores were found
at NFREC in Quincy in July and an
epidemic occurred in non-fungicide plots in
late September and October. Soybean rust
was found on kudzu in Gadsden County
each month of the year but conditions never

existed for widespread movement of spores.
However, the Carolinas did experience rust
on soybeans late in the season. It was
thought to have been moved into the area by
tropical storm Ernesto which moved over
infected areas in Florida before hitting the

David Wright and Jim Marois

Cover Crops

Plant cover crops as soon as possible in
November to get needed cover for next crop.
Many cover crops are killed 4 weeks before
planting in the spring and thick covers are
needed for enhancing soil conditions. Cover
crops can be used for grazing or for help in
nitrogen production. If corn or cotton is to
be planted, 3-5 pounds of crimson clover
may be planted with the grass cover crops to
reduce the nitrogen requirements and to help
in decomposition of the grass cover crop

David Wright

Restricted Use Pesticide Applicator CEU
Program On-Line

Pesticide-related Continuing Education
Credits (CEUs) for farm workers, landscape
maintenance workers, nursery workers, and
others are now available online! You can
access the Pesticide CEU courses through
the UF/IFAS Bookstore Web site.

The individual CEU pages feature a detailed
description, list of approved categories, and
ordering information for each product. The
selection will continue to be updated, so
check back for new courses.

Macromedia Flash Player is required for
viewing the presentations. Visit the Pesticide

Information Office's CEU Modules page for
information about downloading this free
software. This page also provides contact
information for the Pesticide Information
Office in case you need technical assistance
or want to give feedback.

These presentations were produced in
cooperation with the Florida Department of
Agriculture. There are currently 13 CEU
modules available. Each module is narrated
by an IFAS specialist and will take
approximately 50 minutes for the average
person to complete. One CEU has been
approved for completing each module. A
summary of those that are currently
available is listed in the table.

Titles and approved categories of the CEU
modules currently available through the
IFAS/Extension Bookstore.

Title Approved
Poisonous Plants in Ag Row Crop,
Pastures Private
The Value of Pesticides Ag Row Crop, Ag
in Agricultural Crops in Tree Crop,
Florida Private
Understanding Core
Agricultural Pesticide
Licenses under FDACS
Agricultural Crop Pest Ag Tree Crop, Ag
Control Row Crop,
Ornamental &
Turf, Private
Pesticide Labeling Core
Worker Protection Aerial, Ag Tree
Standard Crop, Ag Row
Crop, Forestry,
Ornamental &
Turf, Soil &

Notice of Applications / Aerial, Ag Tree
Posting and Information Crop, Ag Row
Display under WPS Crop, Forestry,
Ornamental &
Turf, Soil &
WPS Training Aerial, Ag Tree
Crop, Ag Row
Crop, Forestry,
Ornamental &
Turf, Soil &
Agricultural Row Crop Ag Row Crop,
Pest Control Private
Application Equipment
Agricultural Application Ag Row Crop,
Equipment Calibration Private
Noxious Weeds in Ag Tree Crop, Ag
Florida Row Crop,
Aquatic, Forestry,
Natural Areas,
Ornamental &
Turf, Right-of-
Way, Private,
Lawn &
Limited Lawn &
Pesticide Formulations Core
Pest Management and Core
Pesticides A Historical
*Approved for Bureau of Entomology and
Pest Control

Fred Fishel

Wheat Varieties for 2006/2007

Small grain prices are expected to be up
some this coming year due to the lower than
expected yields in some parts of the world.

This was an extremely dry year in Florida
with lower than normal yields. More small
grain acreage will be planted due to
potential profits from some of the better

yielding varieties. Yield data can be found
on line at www.griffin.uga.edu/swvt. Some
of the better yielding wheat varieties for
Florida are AGS 2000, which may need a
fungicide, Pioneer 26R61, USG 3209, and a
new one AGS 2060. The older varieties
should be watched closely for disease and
sprayed if needed.

David Wright and Ron Barnett

The use of trade names does not constitute a guarantee or warrant of products named and does not signify approval to the exclusion of similar
Prepared by: J.M. Bennett, Chairman; J.A. Ferrell, Extension Agronomist ii, ii i ,,l ..I.h i F.M. Fishel, Pesticide Coordinator
..l. .1, i ,,i i.i C.R. Rainbolt, Extension Agronomist I.11 ,,1,.11, ,I ,,ll I..ih B.A. Sellers, Extension Agronomist
lii, i, 1i, ,,11i -i..1 D.L. Wright, Extension Agronomist (dlw@ifas.ufl.edu).