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 Table of Contents
 Cotton changes
 Cotton use in the U.S.
 Worldwide impacts of genetic technology...
 Peanut problems
 Soybean rust
 How herbicides work - PROWL
 Where are all these weeds coming...
 What is a 24(c) registration?


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Agronomy notes
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Permanent Link: http://ufdc.ufl.edu/UF00066352/00072
 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: September 2006
 Subjects
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 )
 Notes
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.
Funding: Florida Historical Agriculture and Rural Life
 Record Information
Source Institution: Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location: Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: aleph - 000956365
notis - AER9014
System ID: UF00066352:00072

Table of Contents
    Table of Contents
        Page 1
    Cotton changes
        Page 2
    Cotton use in the U.S.
        Page 2
    Worldwide impacts of genetic technology in cotton
        Page 2
    Peanut problems
        Page 2
    Soybean rust
        Page 2
    How herbicides work - PROWL
        Page 3
        Page 4
    Where are all these weeds coming from? Weed seed banks
        Page 5
    What is a 24(c) registration?
        Page 5
        Page 6
        Page 7
Full Text







AGRONOMY

UNIVERSITY OF
FLORIDA N T
IFAS EXTENSION


Vol. 30:9


September 2006


In Memory of
Martin B. Adjei

The University of Florida and Florida growers lost a dedicated and respected researcher and
extension specialist in a tragic automobile accident on August 15, 2006. Dr. Adjei conducted
considerable research with colleagues throughout Florida and the tropical regions of the world for
more than 28 years, including 9 years with IFAS. His numerous on-farm research/demonstrations
projects and the respect of ranchers earned him the Florida Cattlemen's Researcher of the year
award for 2005. Martin will surely be missed by his research colleagues and especially by the
Florida Cattlemen. A memorial service will be held on August 26 in Arcadia, Florida followed by
burial in Sanderson, Florida on August 27th.


IN THIS ISSUE

COTTON
C otton C changes ........................................................................................... ................ 2
C otton U se in the U .S ................. .......................... ................................ ... ..... ..... 2
Worldwide Impacts of Genetic Technology in Cotton ........ ......................................... 2

PEANUTS
Peanut Problem s .............................. ...................... ............ 2

SOYBEAN
Soybean Rust .......... ......... ............ ............................... ........... .............. 2

WEED CONTROL
H ow H erbicides W ork PR OW L ............................. .................................................. 3
M SM A in Cotton ........................................... ...... ................ 4
Where are all of these weeds coming from?
W eed seed banks ........... .. .......................... ....... .......... .......... ................. 5

MISCELLANEOUS
W hat is a 24(c) registration? .................................... ..................................................... 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.









Cotton Changes

Monsanto Company and Delta and Pine
Land Company announced today that they
have signed a definitive agreement whereby
Monsanto will acquire Delta and Pine Land
Company for $1.5 billion in cash. The
transaction was unanimously approved by
the Boards of Directors of both companies
and is subject to Delta and Pine Land
shareowner approval, antitrust clearance,
and customary closing conditions. The
result may be that new technology will be
available faster to growers and many new
traits developed.

David Wright

Cotton Use in the U.S.

Global cotton use has stayed the same for a
number of years. However, this is now
changing. Many of the cotton mills in the
U.S. have moved overseas in the past 5
years, greatly impacting the textile industry.
In 1995, 8 million bales of cotton were made
into apparel while only 1 million bales are
projected to be used in 2006.

David Wright

Worldwide Impacts of Genetic
Technology in Cotton

India, U.S., and China are the world's
largest producers of cotton. Currently, U.S.
cotton companies are producing hybrid
varieties to introduce traits in other
countries, making pirating of the technology
more difficult. Therefore, hybrid cotton will
allow companies to be compensated for the
technologies they have developed. One in
particular is the Bt trait which is likely to
increase average cotton yields in India by
200 lbs/A. This is because insecticides are


rarely used and insect pests routinely reduce
cotton yield.

David Wright

Peanut Problems

Just when we thought rain made some of the
peanut problems go away, diseases have
begun showing up from plants damaged by
lesser corn stalk borers and cut worms.
Several growers have sprayed pyrethroids
for larvae and have gotten poor control since
the insects were too large to be adequately
controlled. It is important to be sure to use
the right material for the size and kind of
insect being controlled.

With some rainfall in most peanut areas,
peanuts appear to be 2-3 weeks later than
normal due to water stress. The drought has
caused many fields to still be pegging and
flowering heavily. In this scenario, it will be
very important to stay on schedule with
fungicides to keep from having severe
problems with leaf spot with the extended
growing period.

David Wright

Soybean Rust

Soybean rust has been widespread in late
August in both 2005 and 2006. This is
because the high humidity and rainfall that
is common in August hastens spore buildup
and dispersal. Several fungicide studies
were conducted in 2005 on late planted
soybeans. Most of the fungicides tested
were effective against Asian soybean rust if
applied at R1 growth stage, or as soon as
rust was found. Applications made with flat
fan nozzles at 30 psi appeared to do a very
good job of controlling the disease. Yield
increases by nearly 30% when applications









Cotton Changes

Monsanto Company and Delta and Pine
Land Company announced today that they
have signed a definitive agreement whereby
Monsanto will acquire Delta and Pine Land
Company for $1.5 billion in cash. The
transaction was unanimously approved by
the Boards of Directors of both companies
and is subject to Delta and Pine Land
shareowner approval, antitrust clearance,
and customary closing conditions. The
result may be that new technology will be
available faster to growers and many new
traits developed.

David Wright

Cotton Use in the U.S.

Global cotton use has stayed the same for a
number of years. However, this is now
changing. Many of the cotton mills in the
U.S. have moved overseas in the past 5
years, greatly impacting the textile industry.
In 1995, 8 million bales of cotton were made
into apparel while only 1 million bales are
projected to be used in 2006.

David Wright

Worldwide Impacts of Genetic
Technology in Cotton

India, U.S., and China are the world's
largest producers of cotton. Currently, U.S.
cotton companies are producing hybrid
varieties to introduce traits in other
countries, making pirating of the technology
more difficult. Therefore, hybrid cotton will
allow companies to be compensated for the
technologies they have developed. One in
particular is the Bt trait which is likely to
increase average cotton yields in India by
200 lbs/A. This is because insecticides are


rarely used and insect pests routinely reduce
cotton yield.

David Wright

Peanut Problems

Just when we thought rain made some of the
peanut problems go away, diseases have
begun showing up from plants damaged by
lesser corn stalk borers and cut worms.
Several growers have sprayed pyrethroids
for larvae and have gotten poor control since
the insects were too large to be adequately
controlled. It is important to be sure to use
the right material for the size and kind of
insect being controlled.

With some rainfall in most peanut areas,
peanuts appear to be 2-3 weeks later than
normal due to water stress. The drought has
caused many fields to still be pegging and
flowering heavily. In this scenario, it will be
very important to stay on schedule with
fungicides to keep from having severe
problems with leaf spot with the extended
growing period.

David Wright

Soybean Rust

Soybean rust has been widespread in late
August in both 2005 and 2006. This is
because the high humidity and rainfall that
is common in August hastens spore buildup
and dispersal. Several fungicide studies
were conducted in 2005 on late planted
soybeans. Most of the fungicides tested
were effective against Asian soybean rust if
applied at R1 growth stage, or as soon as
rust was found. Applications made with flat
fan nozzles at 30 psi appeared to do a very
good job of controlling the disease. Yield
increases by nearly 30% when applications









Cotton Changes

Monsanto Company and Delta and Pine
Land Company announced today that they
have signed a definitive agreement whereby
Monsanto will acquire Delta and Pine Land
Company for $1.5 billion in cash. The
transaction was unanimously approved by
the Boards of Directors of both companies
and is subject to Delta and Pine Land
shareowner approval, antitrust clearance,
and customary closing conditions. The
result may be that new technology will be
available faster to growers and many new
traits developed.

David Wright

Cotton Use in the U.S.

Global cotton use has stayed the same for a
number of years. However, this is now
changing. Many of the cotton mills in the
U.S. have moved overseas in the past 5
years, greatly impacting the textile industry.
In 1995, 8 million bales of cotton were made
into apparel while only 1 million bales are
projected to be used in 2006.

David Wright

Worldwide Impacts of Genetic
Technology in Cotton

India, U.S., and China are the world's
largest producers of cotton. Currently, U.S.
cotton companies are producing hybrid
varieties to introduce traits in other
countries, making pirating of the technology
more difficult. Therefore, hybrid cotton will
allow companies to be compensated for the
technologies they have developed. One in
particular is the Bt trait which is likely to
increase average cotton yields in India by
200 lbs/A. This is because insecticides are


rarely used and insect pests routinely reduce
cotton yield.

David Wright

Peanut Problems

Just when we thought rain made some of the
peanut problems go away, diseases have
begun showing up from plants damaged by
lesser corn stalk borers and cut worms.
Several growers have sprayed pyrethroids
for larvae and have gotten poor control since
the insects were too large to be adequately
controlled. It is important to be sure to use
the right material for the size and kind of
insect being controlled.

With some rainfall in most peanut areas,
peanuts appear to be 2-3 weeks later than
normal due to water stress. The drought has
caused many fields to still be pegging and
flowering heavily. In this scenario, it will be
very important to stay on schedule with
fungicides to keep from having severe
problems with leaf spot with the extended
growing period.

David Wright

Soybean Rust

Soybean rust has been widespread in late
August in both 2005 and 2006. This is
because the high humidity and rainfall that
is common in August hastens spore buildup
and dispersal. Several fungicide studies
were conducted in 2005 on late planted
soybeans. Most of the fungicides tested
were effective against Asian soybean rust if
applied at R1 growth stage, or as soon as
rust was found. Applications made with flat
fan nozzles at 30 psi appeared to do a very
good job of controlling the disease. Yield
increases by nearly 30% when applications









Cotton Changes

Monsanto Company and Delta and Pine
Land Company announced today that they
have signed a definitive agreement whereby
Monsanto will acquire Delta and Pine Land
Company for $1.5 billion in cash. The
transaction was unanimously approved by
the Boards of Directors of both companies
and is subject to Delta and Pine Land
shareowner approval, antitrust clearance,
and customary closing conditions. The
result may be that new technology will be
available faster to growers and many new
traits developed.

David Wright

Cotton Use in the U.S.

Global cotton use has stayed the same for a
number of years. However, this is now
changing. Many of the cotton mills in the
U.S. have moved overseas in the past 5
years, greatly impacting the textile industry.
In 1995, 8 million bales of cotton were made
into apparel while only 1 million bales are
projected to be used in 2006.

David Wright

Worldwide Impacts of Genetic
Technology in Cotton

India, U.S., and China are the world's
largest producers of cotton. Currently, U.S.
cotton companies are producing hybrid
varieties to introduce traits in other
countries, making pirating of the technology
more difficult. Therefore, hybrid cotton will
allow companies to be compensated for the
technologies they have developed. One in
particular is the Bt trait which is likely to
increase average cotton yields in India by
200 lbs/A. This is because insecticides are


rarely used and insect pests routinely reduce
cotton yield.

David Wright

Peanut Problems

Just when we thought rain made some of the
peanut problems go away, diseases have
begun showing up from plants damaged by
lesser corn stalk borers and cut worms.
Several growers have sprayed pyrethroids
for larvae and have gotten poor control since
the insects were too large to be adequately
controlled. It is important to be sure to use
the right material for the size and kind of
insect being controlled.

With some rainfall in most peanut areas,
peanuts appear to be 2-3 weeks later than
normal due to water stress. The drought has
caused many fields to still be pegging and
flowering heavily. In this scenario, it will be
very important to stay on schedule with
fungicides to keep from having severe
problems with leaf spot with the extended
growing period.

David Wright

Soybean Rust

Soybean rust has been widespread in late
August in both 2005 and 2006. This is
because the high humidity and rainfall that
is common in August hastens spore buildup
and dispersal. Several fungicide studies
were conducted in 2005 on late planted
soybeans. Most of the fungicides tested
were effective against Asian soybean rust if
applied at R1 growth stage, or as soon as
rust was found. Applications made with flat
fan nozzles at 30 psi appeared to do a very
good job of controlling the disease. Yield
increases by nearly 30% when applications









Cotton Changes

Monsanto Company and Delta and Pine
Land Company announced today that they
have signed a definitive agreement whereby
Monsanto will acquire Delta and Pine Land
Company for $1.5 billion in cash. The
transaction was unanimously approved by
the Boards of Directors of both companies
and is subject to Delta and Pine Land
shareowner approval, antitrust clearance,
and customary closing conditions. The
result may be that new technology will be
available faster to growers and many new
traits developed.

David Wright

Cotton Use in the U.S.

Global cotton use has stayed the same for a
number of years. However, this is now
changing. Many of the cotton mills in the
U.S. have moved overseas in the past 5
years, greatly impacting the textile industry.
In 1995, 8 million bales of cotton were made
into apparel while only 1 million bales are
projected to be used in 2006.

David Wright

Worldwide Impacts of Genetic
Technology in Cotton

India, U.S., and China are the world's
largest producers of cotton. Currently, U.S.
cotton companies are producing hybrid
varieties to introduce traits in other
countries, making pirating of the technology
more difficult. Therefore, hybrid cotton will
allow companies to be compensated for the
technologies they have developed. One in
particular is the Bt trait which is likely to
increase average cotton yields in India by
200 lbs/A. This is because insecticides are


rarely used and insect pests routinely reduce
cotton yield.

David Wright

Peanut Problems

Just when we thought rain made some of the
peanut problems go away, diseases have
begun showing up from plants damaged by
lesser corn stalk borers and cut worms.
Several growers have sprayed pyrethroids
for larvae and have gotten poor control since
the insects were too large to be adequately
controlled. It is important to be sure to use
the right material for the size and kind of
insect being controlled.

With some rainfall in most peanut areas,
peanuts appear to be 2-3 weeks later than
normal due to water stress. The drought has
caused many fields to still be pegging and
flowering heavily. In this scenario, it will be
very important to stay on schedule with
fungicides to keep from having severe
problems with leaf spot with the extended
growing period.

David Wright

Soybean Rust

Soybean rust has been widespread in late
August in both 2005 and 2006. This is
because the high humidity and rainfall that
is common in August hastens spore buildup
and dispersal. Several fungicide studies
were conducted in 2005 on late planted
soybeans. Most of the fungicides tested
were effective against Asian soybean rust if
applied at R1 growth stage, or as soon as
rust was found. Applications made with flat
fan nozzles at 30 psi appeared to do a very
good job of controlling the disease. Yield
increases by nearly 30% when applications








were made at first bloom and again 2 or 3
weeks later. Fungicides applied after R5
stage are not expected to increase yields.

David Wright

How Herbicides Work PROWL

Prowl is the trade name for the herbicide
that contains the active ingredient
pendimethalin. Prowl is registered for use in
a variety of crops, including corn, cotton,
peanuts and soybeans. It is also registered
for use in certain turfgrasses and many fruit
and nut crops. Pendimethalin is active on
many grasses and certain broadleaf weed
species. In general, broadleaves controlled
by pendimethalin are "small-seeded" and
include weeds such as pigweeds, Florida
pusley and common lambsquarters.

Pendimethalin is applied to the soil surface
for preemergence weed control. The
herbicide must be incorporated soon after
application with tillage or left on the soil
surface to be incorporated with rainfall or
irrigation. If incorporation does not occur
within 7 days after application, breakdown
due to photolysis (photodegradation) will
occur and deactivate the herbicide.
Pendimethalin can be applied over the top of
many crops without harmful effects, but
only has activity on weeds that have not
germinated. Pendimethalin does not have
postemergence activity.

Pendimethalin is classified as a growth
inhibiting herbicide, or sometimes it is
called a mitotic inhibitor. This herbicide
blocks the process of mitosis, the process
whereby cells divide to form new cells.
More specifically, pendimethalin binds to
tubulin, which comprises the spindle fibers.
As seen below, spindle fibers "pull" the
chromosomes to each newly developing cell.
The binding of pendimethalin to tubulin
does not allow the spindle fibers to form,
thus preventing cell division.


Figure 1 Mitosis adapted from
www.phoenix 5.org

Pendimethalin is effective on new and
rapidly dividing tissues; most often observed
in developing seedlings. Specifically, this
herbicide prevents shoot and root growth in
susceptible seedlings. Because seedlings
have only 2 growing points (the tips of
shoots and roots), blocking both or one of
these areas will result in death. Plants that
have established root systems are not
generally affected. However, pendimethalin
will cause root pruning in certain instances.

The big question then becomes, "If Prowl
inhibits root growth, why doesn't it hurt my
crop?" The answer can be explained in two
ways: uptake and water solubility. First of
all pendimethalin is not very soluble in
water, but is readily moving into plant
tissues. However, due to this lack of water
solubility, pendimethalin does not move
within the plant. Essentially, it behaves as a
contact herbicide. Since the growing point
is the susceptible tissue, there must be
critical level of pendimethalin in the soil at
the region where the shoot and/or root
growing points exist. This is called the zone
of activity. This is shown in the figure
below.








Monocots are susceptible to pendimethalin
because their growing regions (both root and
shoot) are directly in the herbicide treated
zone. As grasses germinate, the shoot and
root tips are exposed to lethal levels of the
herbicide and stop growing; thus killing the
seedling. Dicots will germinate below the
treatment zone, or lower in the zone where a
minimal amount of root uptake occurs.
Additionally, the growing point of the shoot
is shielded by the cotyledons as the shoot
emerges, and this limits the amount of
herbicide that can be taken up directly by the
shoot tip.

In a nutshell:

1. Pendimethalin must be applied to the
soil surface and watered in, or
incorporated to prevent losses from
photodegradation.
2. Due to low water solubility,
pendimethalin does not move
appreciably within the soil column; it
stays in the top 1-3 inches.
3. Pendimethalin is readily absorbed into
cells, but does not move within plant
tissues.
4. Pendimethalin must contact the
susceptible growing points to be
effective, therefore the growing tips
must be in the zone where pendimethalin
is applied.
5. Pendimethalin will prevent mitosis in
any cell tissues, but established plants do
not have dividing tissues (growing tips)
in the herbicide treated zone.

Greg MacDonald

MSMA in Cotton

Now that the cotton crop is maturing, it is an
ideal time to look back over the season and
evaluate your weed control program. Were
any new weeds present this year? Was
control less than desirable on any weeds?
Basically, the questions should center on


whether changes in the weed control
program need to be made for next year. If
so, you might want to consider returning to
MSMA.

MSMA has long been used over-the-top in
cotton early in the season and post-directed
applications late in the season. Although
MSMA does not have a great fit early in the
season due to cotton injury issues, it remains
an excellent option for post-directed
applications. I believe there are two reasons
why MSMA should be used more often in
cotton.

First, more residual herbicides (Direx,
Valor, Caparol, Prowl, etc) should be
sprayed at layby. When layby applications
are typically made, there is still a lot of
growing season left giving plenty of time for
weeds to germinate and become established.
Yes, glyphosate is excellent at controlling
weeds of all sizes, but the lack of residual
activity often often increases the occurrence
of late-season weeds. Therefore, residual
herbicides offer the unique ability to extend
weed control later into the season.
However, these residual herbicides often
lack significant grass and sedge activity. By
adding 2.5 pt/A of MSMA, grass and sedge
activity are dramatically improved at a
relatively low cost.

Secondly, MSMA + residual herbicides
offer differing herbicide modes of action to
the weed control program and significantly
reduce the probability of developing
herbicide resistant weeds. In Georgia,
glyphosate-resistant Palmer amaranth was
verified in 2005. The primary reason for
resistance in this field was because
glyphosate was the only herbicide used for
weed control for over 7 years. Repeated
applications of the same herbicide, or
herbicides with the same mode of action,
leads to high levels of selection pressure
and, in time, herbicide resistant weeds.
However, adding MSMA to the herbicide








program will dramatically reduce the
occurrence of resistant weeds.

MSMA is a very old herbicide, but it
maintains great usefulness in cotton
production. If late-season sedges are a
problem, consider adding MSMA to the
program. If you plan to use residual
herbicides at layby, MSMA is an ideal tank-
mix partner.

Jason Ferrell

Where are all of these weeds coming
from? Weed seed banks.

Despite the hard work of growers,
continuing research by weeds scientists, and
improvements in application technologies,
weeds are a persistent problem for most
growers. Why is it that a grower can
achieve near perfect weed control one
season, yet have to battle the same weed
problem the next? It turns out that the old
adage "One year's seeding- seven years'
weeding" is accurate. When weed seeds fall
to the ground, they become part of a weed
seed bank in the soil and can cause weedy
conditions for many years.

Even in the cleanest fields it is likely that a
few weeds will escape control and produce
seed. Depending on the species, a single
plant can produce anywhere from a few to
thousands of seeds. It has been estimated
that less than 10% of the viable weed seeds
produced each year germinate. The rest
accumulate on the surface and in the soil to
form the weed seed bank. The total number
of seeds in agricultural soils can be
enormous. Most research estimates the
number to be between 13,000,000 and
435,000,000 seeds per acre.

Although a large number of the buried seeds
are lost to decay, predation, and physical
damage, some species can remain viable for
decades. Some weed seeds enter a state of
dormancy, a relatively inactive or resting


condition, that slows down or stops weed
seed germination. This allows them to
escape or avoid exposure to control practices
that target emerging and emerged weed
seedlings.

Preventing weed seed development may not
have an immediate impact, but will help
reduce soil seed banks in the long term. As
with other weed management strategies an
integrated approach is best. Chemical and
mechanical weed control practices should be
timed to prevent seed development and
dispersal. Keeping canals and field edges
clean can also help reduce seed rain. In
Florida, many weeds can grow and produce
seed year round, thus it is critical to
maintain weed control during fallow
periods. Cleaning cultivation and harvest
equipment between fields can also prevent
moving seeds from one location to another.

Curtis Rainbolt

What is a 24(c) registration?

Consider the two following scenarios:

A new pesticide application
technology has been developed
specifically for nursery producers;
however, current pesticide labeling
does not support its practice. The
new technology could result in fewer
pounds of pesticides introduced into
the environment and less applicator
exposure.
An insect pest introduced into
Florida during the 1960s has shown
continuous activity on vegetable
crops. Producers recently discover
that a pesticide already in use for
other pests will also control this pest,
but it isn't listed on the pesticide's
label.

These scenarios have a common theme --
pesticides that have been in use over the
years could be adapted to fit unique








program will dramatically reduce the
occurrence of resistant weeds.

MSMA is a very old herbicide, but it
maintains great usefulness in cotton
production. If late-season sedges are a
problem, consider adding MSMA to the
program. If you plan to use residual
herbicides at layby, MSMA is an ideal tank-
mix partner.

Jason Ferrell

Where are all of these weeds coming
from? Weed seed banks.

Despite the hard work of growers,
continuing research by weeds scientists, and
improvements in application technologies,
weeds are a persistent problem for most
growers. Why is it that a grower can
achieve near perfect weed control one
season, yet have to battle the same weed
problem the next? It turns out that the old
adage "One year's seeding- seven years'
weeding" is accurate. When weed seeds fall
to the ground, they become part of a weed
seed bank in the soil and can cause weedy
conditions for many years.

Even in the cleanest fields it is likely that a
few weeds will escape control and produce
seed. Depending on the species, a single
plant can produce anywhere from a few to
thousands of seeds. It has been estimated
that less than 10% of the viable weed seeds
produced each year germinate. The rest
accumulate on the surface and in the soil to
form the weed seed bank. The total number
of seeds in agricultural soils can be
enormous. Most research estimates the
number to be between 13,000,000 and
435,000,000 seeds per acre.

Although a large number of the buried seeds
are lost to decay, predation, and physical
damage, some species can remain viable for
decades. Some weed seeds enter a state of
dormancy, a relatively inactive or resting


condition, that slows down or stops weed
seed germination. This allows them to
escape or avoid exposure to control practices
that target emerging and emerged weed
seedlings.

Preventing weed seed development may not
have an immediate impact, but will help
reduce soil seed banks in the long term. As
with other weed management strategies an
integrated approach is best. Chemical and
mechanical weed control practices should be
timed to prevent seed development and
dispersal. Keeping canals and field edges
clean can also help reduce seed rain. In
Florida, many weeds can grow and produce
seed year round, thus it is critical to
maintain weed control during fallow
periods. Cleaning cultivation and harvest
equipment between fields can also prevent
moving seeds from one location to another.

Curtis Rainbolt

What is a 24(c) registration?

Consider the two following scenarios:

A new pesticide application
technology has been developed
specifically for nursery producers;
however, current pesticide labeling
does not support its practice. The
new technology could result in fewer
pounds of pesticides introduced into
the environment and less applicator
exposure.
An insect pest introduced into
Florida during the 1960s has shown
continuous activity on vegetable
crops. Producers recently discover
that a pesticide already in use for
other pests will also control this pest,
but it isn't listed on the pesticide's
label.

These scenarios have a common theme --
pesticides that have been in use over the
years could be adapted to fit unique








production situations within the state. How
can producers call attention to these
situations and convince state and federal
agencies to allow special use of pesticides?
By applying for Special Local Need
Registration, also known as a 24(c). Both
groups of producers bring their situations to
the attention of scientists at the University of
Florida and their respective commodity
associations. In turn, these groups provide
supporting evidence to the Florida
Department of Agriculture and Consumer
Services (FDACS). FDACS forwards the
supporting documents to the U.S. EPA for
review and consideration of use approval.
With these groups working cooperatively,
special local needs labels are written
specifically for Florida to address these
unique situations.

A special local need means an existing or
imminent pest problem has been identified
by producers of a given agricultural
commodity within Florida. Major pieces of
supporting information required for such a
use is that the 24(c) use:

Is covered by necessary tolerances or
other clearances under the Federal
Food, Drug, and Cosmetic Act. A
tolerance is a term that is used
legally to describe the amount of a
pesticide's residue that may remain
on or in a treated crop according to
federal regulation.
Registration for the same use has not
previously been denied, disapproved,
suspended, or canceled by the EPA,
or voluntarily canceled by the
pesticide's registrant. This can occur
because of health or environmental
concerns about an ingredient
contained in the pesticide product. If
new data become available that
resolve the EPA's concerns, a 24(c)
may be considered.


The 24(c) registration is in
accordance with the intent of the
Federal Insecticide, Fungicide, and
Rodenticide Act (FIFRA).
If the proposed use or product falls
into one of the following categories,
FDACS must determine that it will
not cause unreasonable adverse
effects on humans or the
environment:
o Use of a product which has a
composition not similar to
any current federally
registered product.
o Use of a product involving a
use pattern not similar to any
federally registered use of the
same product or a product of
similar composition.
o Use of a product for which
other uses of the same
product, or uses of a product
of similar composition, has
had registration denied,
disapproved, suspended, or
canceled by the EPA.

FDACS can consider uses such as the
following for 24(c) registrations:

New method of application or timing
of application.
New pest.
Altered rate.
Application in particular soil type.
New product/different formulation.
Products useful in managing
pesticide resistance in a particular
crop.

A price differential between products is
generally not viewed as a legitimate
justification for a 24(c) registration.

FDACS can issue 24(c) registrations for the
purpose of avoiding the buildup of pest
resistance. Documenting this need is met if:








The pesticide with the 24(c) registration has
a different mode of action from products
that are already available; or if registering
two pesticides under a 24(c), they must have
different modes of action.

There are currently registered
pesticides; however, there is only
one effective mode of action
remaining.
The pest has a history of developing
resistance to existing or canceled
pesticides and this resistance is
documented through field studies or
references to field studies.
The currently registered pesticide has
a history of resistance which is
documented through field studies or
references to field studies.
Evidence must exist that the pest(s),
use patterns, and climatic conditions
for the proposed use under the 24(c)
is the same or substantially similar to
situations where resistance has been
documented.
A brief description of the resistance
management plan and how the
pesticide's use under a 24(c)
registration will fit into the plan.

Each state is encouraged to set time limits
for 24(c) registrations. Because 24(c)
registrations are considered by FIFRA to be
section 3 registrations (fully registered) after
90 days, EPA generally is not in a position
to impose time limits on 24(c) registrations.
So long as the registrant of the 24(c) is in
FIFRA's compliance requirements for
maintaining the registration by paying its
fees, EPA will not cancel the registration,
even if a state has done so. An exception is a
situation in which a registrant voluntarily


cancels the product or EPA has a cause to
issue a notice of intent to cancel.

An example of a 24(c) registration that was
granted in Florida during 2005 involved a
new application of an older pesticide. The
herbicide Surflan received its patent in
1968, but current labels prohibit its
application by air. The 2005 approved 24(c)
registration by FDACS approved aerial
application to caladiums in Florida. Another
example of a recent granting of a 24(c)
registration involved altering planting
restrictions. The fungicide Switch is
applied to certain vegetable crops and
strawberries. In Florida, a 24(c) registration
was granted to allow for planting of
subsequent crops on the Switch label
anytime following its last application and a
30-day waiting period for crops not listed on
its label. Another recent 24(c) registration
that was recently approved involved a new
timing of application. Paraquat is an older
herbicidal active ingredient with Syngenta
Crop Protection as the current registrant for
the product Gramoxone. The full section 3
label allows only for post-directed
applications of the product. However, the
new supplemental label now allows the
product to be applied as a post-harvest
desiccant to strawberry following harvest.

Applicators who wish to use a product in a
manner approved by the 24(c) registration
are required to have in their possession a
copy of the supplemental 24(c) label at the
time of application as well as the Section 3
label. They are also required to fully follow
all applicable directions, restrictions,
Worker Protection Standard requirements,
and precautions on the EPA-registered label.

Fred Fishel


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
products.
Prepared by: J.M. Bennett, Chairman; J.A. Ferrell, Extension Agronomist ijaferrell a itfa.uftl.edu F.M. Fishel, Pesticide Coordinator
..h.. .,I ,,i1 ..I,, C.R. Rainbolt, Extension Agronomist .11 ,1...11 I i ,,il ..h B.A. Sellers, Extension Agronomist
., I., ,I ii,,i ...i D.L. Wright, Extension Agronomist (dlw@ifas.ufl.edu).