• TABLE OF CONTENTS
HIDE
 Front Cover
 Credits
 Table of Contents
 Introduction
 Effect of 2,4-D on plants
 Types of 2,4-D
 2,4-D acid content
 Weeds that can be controlled
 Rate of application
 Use of 2,4-D in certain tolerant...
 2,4-D damage to susceptible...
 Differential tolerance of certain...
 Suitable equipment and methods...
 Practical aspects of field application...
 Precautions to be taken in the...
 Summary
 Acknowledgement
 Appendix














Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 532
Title: 2,4-D for post-emergence weed control in the Everglades
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Permanent Link: http://ufdc.ufl.edu/UF00027655/00001
 Material Information
Title: 2,4-D for post-emergence weed control in the Everglades
Series Title: Bulletin - University of Florida Agricultural Experiment Station ; 532
Physical Description: Book
Language: English
Creator: Seale, Charles C.
Randolph, John W.
Guzman, Victor L.
Publisher: University of Florida Agricultural Experiment Station
Publication Date: 1953
 Record Information
Bibliographic ID: UF00027655
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.

Table of Contents
    Front Cover
        Page 1
    Credits
        Page 2
        Page 3
    Table of Contents
        Page 4
    Introduction
        Page 5
    Effect of 2,4-D on plants
        Page 5
    Types of 2,4-D
        Page 6
    2,4-D acid content
        Page 7
    Weeds that can be controlled
        Page 8
    Rate of application
        Page 9
        Page 10
    Use of 2,4-D in certain tolerant crops
        Page 11
        Page 12
        Page 13
    2,4-D damage to susceptible crops
        Page 14
        Page 15
        Page 16
    Differential tolerance of certain susceptible crops to 2,4-D
        Page 17
    Suitable equipment and methods for the application of 2,4-D
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
        Page 26
        Page 27
        Page 28
        Page 29
    Practical aspects of field application of 2,4-D
        Page 30
    Precautions to be taken in the use of 2,4-D
        Page 30
    Summary
        Page 31
    Acknowledgement
        Page 32
    Appendix
        Page 33
        Page 34
        Page 35
        Page 36
Full Text


December 1953


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
WILLARD M. FIFIELD, Director
GAINESVILLE, FLORIDA

(A contribution from the Everglades Experiment Station)









2,4-D


For Post-Emergence Weed Control


in the Everglades

CHARLES C. SEALE, JOHN W. RANDOLPH
and VICTOR L. GUZMAN












Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


Bulletin 532











BOARD OF CONTROL
Hollis Rinehart, Chairman, Miami
J. Lee Ballard, St. Petersburg
Fred H. Kent, Jacksonville
Wm. H. Dial, Orlando '
Mrs. Alfred I. duPont, Jacksonville
George W. English, Jr., Ft. Lauderdale
W. Glenn Miller, Monticello
W. F. Powers, Secretary, Tallahassee
EXECUTIVE STAFF
J. Hillis Miller, Ph.D., Presidents
J. Wayne Reit, Ph.D., Provost for Agr.3
Willard M. Fifleld, M.S., Director
J. R. Beckenbach, Ph.D., Asso. Director
L. O. Gratz, Ph.D., Assistant Director
Rogers L. Bartley, B.S., Admin. Mgr.s
Gee. R. Freeman, B.S., Farm Superintendent

MAIN STATION, GAINESVILLE
AGRICULTURAL ECONOMICS
H. G. Hamilton, Ph.D., Agr. Economist'
R. E. L. Greene, Ph.D., Agr. Economist
M. A. Brooker, Ph.D., Agr. Economists
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Agr. Economist
D. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate
M. R. Godwin, Ph.D., Associates
W. K. McPherson, M.S., Economist3
Eric Thor, M.S., Asso. Agr. Economist
Cecil N. Smith, M.A., Asso. Agr.. Economist
Levi A. Powell, Sr., M.S.A., Assistant
Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agri. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statistician'
J. B. Owens, B.S.A., Agr. Statistician 2
F. T. Calioway, M.S., Agr. Statistician
AGRICULTURAL ENGINEERING
Frazier Rogers, M.S.A., Agr. Engineer s
J. M. Myers, M.S.A., Asso. Agr. Engineer
J. S. Norton, M.S., Asst. Agr. Engineer
AGRONOMY
Fred H. Hull, Ph.D., Agronomist12
G. B. Killinger Ph.D. Agronomist
H. C. Harris, Ph.D., Agronomist
R. W. Bledsoe, Ph.D., Agronomist
W. A. Carver, Ph.D., Agronomist
Fred A. Clark, M.S., Associate 2
E. S. Horner, Ph.D., Assistant
A. T. Wallace, Ph.D., Assistant
D. E. McCloud, Ph.D., Assistant3
G. C. Nutter, Ph.D., Asst. Agronomist
I. M. Wofford, Ph.D., Asst. Agronomist
ANIMAL HUSBANDRY AND NUTRITION
T. J. Cunha, Ph.D., Animal Husbandman 1'
G. K. Davis, Ph.D., Animal Nutritionist 3
R. L. Shirley, Ph.D., Biochemist
A. M. Pearson, Ph.D., Asso. An. Husb.3
John P. Feaster, Ph.D., Asst. An. Nutri.
H. D. Wallace, Ph.D., Asst. An. Husb.S
M. Koger, Ph.D., An. Husbandman T
J. F. Hentges, Jr., Ph.D., Asst. An. Husb. S
L. R. Arrington, Ph.D., Asst. An. Husb.
A. C. Warnick, Ph.D., Asst. Physiologist
DAIRY SCIENCE
E. L. Fouts, Ph.D., Dairy Technologist's
R. B. Becker, Ph.D., Dairy Husbandman 3
S. P. Marshall, Ph.D., Asso. Dairy Husb.3
W. A. Krienke, M.S., Asso. Dairy Tech.3
P. T. Dix Arnold, M.S.A., Asso. Dairy Husb. 2
Leon Mull, Ph.D., Asso. Dairy Tech.'
H. H. Wilkowske, Ph.D., Asst. Dairy Tech.3
James M. Wing, Ph.D., Asst. Dairy Husb.


EDITORIAL
J. Francis Cooper, M.S.A., Editor 3
Clyde Beale, A.B.J., Associate Editor
J. N. Joiner, B.S.A., Assistant Editor 3
William G. Mitchell, A.B.J., Assistant Editor
Samuel L. Burgess, A.B.J., Assistant Editor 3
ENTOMOLOGY
A. N. Tissot, Ph.D., Entomologist 1
L. C. Kuitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
F. A. Robinson, M.S., Asst. Apiculturist
R. E. Waites, Ph.D., Asst. Entomologist
S. H. Kerr, Ph.D., Asst. Entomologist
HOME ECONOMICS
Ouida D. Abbott, Ph.D., Home Econ.1
R. B. French, Ph.D., Biochemist
HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist
F. S. Jamison, Ph.D., Horticulturist84
Albert P. Lorz, Ph.D., Horticulturist
R. K. Showalter, M.S., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. H. Sharpe, M.S., Asso. Horticulturist
V. F. Nettles, Ph.D., Asso. Horticulturist
F. S. Lagasse, Ph.D., Horticulturists
R. D. Dickey, M.S.A., Asso. Hort.
L. H. Halsey, M.S.A., Asst. Hort.
C. B. Hall, Ph.D., Asst. Horticulturist
Austin Griffiths, Jr., B.S., Asst. Hort.
S. E. McFadden, Jr., Ph.D., Asst. Hort.
C. H. VanMiddelem, Ph.D., Asst. Biochemist
Buford D. Thompson; M.S.A., Asst. Hort.
M. W. Hoover, M.S.A., Asst. Hort.
LIBRARY
Ida Keeling Cresap, Librarian
PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist 13
Phares Decker, Ph.D., Plant Pathologist
Erdman West, M.S., Botanist & Mycologist 3
Robert W. Earhart, Ph.D., Plant Path.2
Howard N. Miller, Ph.D., Asso. Plant Path.
Lillian E. Arnold, M.S., Asso. Botanist
C. W. Anderson, Ph.D., Asst. Plant Path.
POULTRY HUSBANDRY
N. R. Mehrhof, M.Agr., Poultry Husb.1 8
J. C. Driggers, Ph.D., Asso. Poultry Husb.8
SOILS
F. B. Smith, Ph.D., Microbiologist'1
Gaylord M. Volk, Ph.D., Soils Chemist
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
Ralph G. Leighty, B.S., Asst. Soil Surveyor 2
G. D. Thornton, Ph.D., Microbiologist
C. F, Eno, Ph.D., Asst. Soils Microbiologist
H. W. Winsor, B.S.A., Assistant Chemist
R. E. Caldwell, M.S.A., Asst. Chemist 4
V. W. Carlisle, B.S., Asst. Soil Surveyor
J. H. Walker, M.S.A., Asst. Soil Surveyor
William K. Robertson, Ph.D., Asst. Chemist
0. E. Cruz, B.S.A., Asst. Soil Surveyor
W. G. Blue, Ph.D., Asst. Biochemist
J. G. A. Fiskel, Ph.D., Asst. Biochemist I
L. C. Hammond, Ph.D., Asst. Soil Physicist 8
H. L. Breland, Ph.D., Asst. Soils Chem.
VETERINARY SCIENCE
D. A. Sanders, D.V.M., Veterinarian '
M. W. Emmel, D.V.M., Veterinarian
C. F. Simpson, D.V.M., Asso. Veterinarian
L. E. Swanson, D.V.M., Parasitologist
W. R. Dennis, D.V.M., Asst. Parasitologist
E. W. Swarthout, D.V.M., Asso. Poultry
Pathologist (Dade City)










BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
W. C. Rhoades, M.S., Entomologist in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
L. G. Thompson, Jr., Ph.D., Soils Chemist
W. H. Chapman, M.S., Agronomist
Frank S. Baker, Jr., B.S., Asst. An. Husb.
Frank E. Guthrie, Ph.D., Asst. Entomologist
Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist
Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist
Mobile Unit, Pensacola
R. L. Smith, M.S., Associate Agronomist
Mobile Unit, Chipley
J. B. White, B.S.A., Associate Agronomist

CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, Ph.D., Asso. Plant Path.
C. R. Stearns, Jr., B.S.A., Asso. Chemist
J. W. Sites, Ph.D., Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist
H. J. Reitz, Ph.D., Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist
R. Hendrickson, B.S., Asst. Chemist
Ivan Stewart, Ph.D., Asst. Biochemist
D. S. Prosser, Jr., B.S., Asst. Engineer
R. W. Olsen, B.S., Biochemist
F. W .Wenzel, Jr., Ph.D., Chemist
Alvin H. Rouse, M.S., Asso. Chemist
H. W. Ford, Ph.D., Asst. Horticulturist
L. C. Knorr, Ph.D., Asso. Histologist4
R. M. Pratt, Ph.D., Asso. Ent.-Pathologist
W. A. Simanton, Ph.D., Entomologist
E. J. Deszyck, Ph.D., Asso. Horticulturist
C. D. Leonard, Ph.D., Asso. Horticulturist
W. T. Long, M.S., Asst. Horticulturist
M. H. Muma, Ph.D., Asso. Entomologist
F. J. Reynolds, Ph.D., Asso. Hort.
W. F. Spencer, Ph.D., Asst. Chem.
R. B. Johnson, Ph.D., Asst. Entomologist
W. F. Newhall, Ph.D., Asst. Entomologist
W. F. Grierson-Jackson, Ph.D., Asst. Chem.
Roger Patrick, Ph.D., Bacteriologist
Marion F. Oberbacher, Ph.D., Asst. Plant
Physiologist
Evert J. Elvin, B.S., Asst. Horticulturist
R. C. J. Koo, Ph.D., Asst. Biochemist
J. R. Kuykendall, Ph.D., Asst. Horticulturist

EVERGLADES STATION, BELLE GLADE
W. T. Forsee, Jr., Ph.D., Chemist in Charge
R. V. Allison, Ph.D., Fiber Technologist
Thomas Bregger, Ph.D., Physiologist
J. W. Randolph, M.S., Agricultural Engr.
R. W. Kidder, M.S., Asso. Animal Hush.
C. C. Seale, Associate Agronomist
N. C. Hayslip, B.S.A. Asso. Entomologist
E. A. Wolf, M.S., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist
W. G. Genung, M.S., Asst. Entomologist
Robert J. Allen, Ph.D., Asst. Agronomist
V. E. Green, Ph.D., Asst. Agronomist
J. F. Darby, Ph.D., Asst. Plant Path.
V. L. Guzman, Ph.D., Asst. Hort.
J. C. Stephens, B.S., Drainage Engineer2
A. E. Kretschmer, Jr., Ph.D., Asst. Soils
Chem.
Charles T. Ozaki, Ph.D., Asst. Chemist
Thomas L. Meade, Ph.D., Asst. An. Nutri.
D. S. Harrison, M.S., Asst. Agri. Engr.


F. T. Boyd, Ph.D., Asso. Agronomist
M. G. Hamilton, Ph.D., Asst. Horticulturist
J. N. Simons, Ph.D., Asst. Virologist
D. N. Beardsley, M.S., Asst. Animal Hush.
SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
D. 0. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Robert A. Conover, Ph.D., Plant Path.
John L. Malcolm, Ph.D., Asso. Soils Chemist
R. W. Harkness, Ph.D., Asst. Chemist
R. Bruce Ledin, Ph.D., Asst. Hort.
J. C. Noonan, M.S., Asst. Hort.
M. H. Gallatin, B.S., Soil Conservationist
WEST CENTRAL FLORIDA STATION,
BROOKSVILLE
Marian W. Hazen, M.S., Animal Husband-
man in Charge2
RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Agronomist
D. W. Jones, M.S., Asst. Soil Technologist
CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. W. Wilson, ScD., Entomologist
P. J. Westgate, Ph.D., Asso. Hort.
Ben F. Whitner, Jr., B.S.A., Asst. Hort.
Geo. Swank, Jr., Ph.D., Asst. Plant Path.
WEST FLORIDA STATION, JAY
C. E. Hutton, Ph.D., Vice-Director in Charge
H. W. Lundy, B.S.A., Associate Agronomist
SUWANNEE VALLEY STATION,
LIVE OAK
G. E. Ritchey, M.S., Agronomist in Charge
GULF COAST STATION, BRADENTON
E. L. Spencer, Ph.D., Soils Chemist in Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. A. Kelbert, Asso. Horticulturist
Robert O. Magie, Ph.D., Plant Pathologist
J. M. Walter, Ph.D., Plant Pathologist
S. S. Woltz, Ph.D., Asst. Horticulturist
Donald S. Burgis, M.S.A., Asst. Hort.
C. M. Geraldson, Ph.D., Asst. Horticulturist

FIELD LABORATORIES
Watermelon, Grape, Pasture-Leesburg
J. M. Crall, Ph.D., Associate Plant Path-
ologist Acting in Charge
C. C. Helms, Jr., B.S., Asst. Agronomist
L. H. Stover, Assistant in Horticulture
Strawberry-Plant City
A. N. Brooks', Ph.D., Plant Pathologist
Vegetables-Hastings
A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist
T. M. Dobrovsky, Ph.D., Asst. Entomologist
Pecans-Monticello
A. M. Phillips, B.S., Asso. Entomologist2
John R. Large, M.S., Asso. Plant Path.
Frost Forecasting-Lakeland
Warren O. Johnson, B.S., Meteorologist in
Charge2
1Head of Department
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
On leave















CONTENTS


INTRODUCTION ..........-.... .......-... ..--.. ...

EFFECT OF 2,4-D ON PLANTS ............--- ... ... .. ......

TYPES OF 2,4-D ........... ............ .... --------------------

2,4-D ACID CONTENT ...... ....... -..... ....- -... -

WEEDS THAT CAN BE CONTROLLED .................----- ..-----

RATE OF APPLICATION ..--........... --------------------

USE OF 2,4-D IN CERTAIN TOLERANT CROPS ........................

Pastures and Turf ........-..... ....- ..... ..- --


Corn .........

Sugar Cane


PAGE

-.. -.- -... 5


.. --------... .....- 5
-~5

6

7

-~8
...... .... ......... 6

-. --.-.-.-- ..- 7

......................... 8

.... -.......--... 9



.. .. ..... ... 11

..... ... .... 12

... .... 14


R ice .. ..... ...... -- ........ --... ------- ----....-------------.......... ---- --- 14

R am ie ..- .... ........ ..... ... .. .. --- -. ------- --.. --------. -- 14

2,4-D DAMAGE TO SUSCEPTIBLE CROPS -......... ... ... ---..-.---- ------.-------- 14

DIFFERENTIAL TOLERANCE OF CERTAIN SUSCEPTIBLE CROPS TO 2,4-D ..... 17

SUITABLE EQUIPMENT AND METHODS FOR THE APPLICATION OF 2,4-D .. 18

N ozzles ........ ....--...........- ...... .. ........ ----- --- ---------.... --.. ..-- -..- 20

Boom s ............-..... ................. .... ... ....- ----- -- 27

Pum ps .... ...........- .....................-........- ...... -----.. ------ ---------.. -- 27

Screens .---.. -... ... ......- -. -- --.. -- --... ---. --- -- 2 28

PRACTICAL ASPECTS OF FIELD APPLICATION OF 2,4-D .........-....-....-----.... 30

PRECAUTIONS TO BE TAKEN IN THE USE OF 2,4-D ....-.-------------- ..----- 30

SUMMARY ................ ----. -.--. --- ...- -- ----------.------ --. -- 31

A CKNOW LEDGMENTS .......... ....- ----- .-.-. ....--- ----.. -. ------.--- --.... --. ... 32

A PPENDIX .--..-- .- -- .--.- --. ------ .. -- -- ---- ... -- -------- --- ----. ...- 33


---- -------









2,4-D for Post-Emergence Weed Control

in the Everglades

CHARLES C. SEALE, JOHN W. RANDOLPH
and VICTOR L. GUZMAN 1

INTRODUCTION
Scientific work conducted in this country and elsewhere a
little over a decade ago demonstrated that the chemical sub-
stance commonly known as 2,4-D (2,4-dichlorophenoxyacetic
acid) possesses plant-killing properties. Since that time, 2,4-D
has been used in increasing quantity for the control of a wide
variety of broadleaf weeds in resistant crops. Statistics show
that in 1951 over 34 million pounds of the herbicide 2 were manu-
factured in the United States.
Experimental work with 2,4-D for weed control in pastures,
turf and certain field crops has been done since 1945 at the
Everglades Experiment Station. Weed control work is under
way at present on sugar cane and vegetable crops using 2,4-D
and a number of other herbicides.
There are several benefits to be obtained from the use of
2,4-D for the control of weeds. However, improper handling
of the herbicide in recent years has been the cause of consider-
able damage to vegetable and other sensitive crops in the Ever-
glades and elsewhere. This bulletin offers information on the
proper use of 2,4-D for post-emergence weed control in the
Everglades.

EFFECT OF 2,4-D ON PLANTS
Plants produce in their systems minute quantities of certain
chemical substances which regulate their rate of growth. These
substances are commonly called plant hormones or growth regu-
lators. Early investigators studying growth-regulating sub-
stances found that certain chemicals such as 2,4-D behave in
a similar manner. The application of 2,4-D to susceptible plants
stimulates abnormal growth, because the natural balance of
growth processes is distorted.
1Associate Agronomist, Agricultural Engineer and Interim Assistant
Horticulturist, respectively, Everglades Experiment Station, Belle Glade,
Florida.
U. S. Tariff Commission. Private communication dated June 13, 1952.









2,4-D for Post-Emergence Weed Control

in the Everglades

CHARLES C. SEALE, JOHN W. RANDOLPH
and VICTOR L. GUZMAN 1

INTRODUCTION
Scientific work conducted in this country and elsewhere a
little over a decade ago demonstrated that the chemical sub-
stance commonly known as 2,4-D (2,4-dichlorophenoxyacetic
acid) possesses plant-killing properties. Since that time, 2,4-D
has been used in increasing quantity for the control of a wide
variety of broadleaf weeds in resistant crops. Statistics show
that in 1951 over 34 million pounds of the herbicide 2 were manu-
factured in the United States.
Experimental work with 2,4-D for weed control in pastures,
turf and certain field crops has been done since 1945 at the
Everglades Experiment Station. Weed control work is under
way at present on sugar cane and vegetable crops using 2,4-D
and a number of other herbicides.
There are several benefits to be obtained from the use of
2,4-D for the control of weeds. However, improper handling
of the herbicide in recent years has been the cause of consider-
able damage to vegetable and other sensitive crops in the Ever-
glades and elsewhere. This bulletin offers information on the
proper use of 2,4-D for post-emergence weed control in the
Everglades.

EFFECT OF 2,4-D ON PLANTS
Plants produce in their systems minute quantities of certain
chemical substances which regulate their rate of growth. These
substances are commonly called plant hormones or growth regu-
lators. Early investigators studying growth-regulating sub-
stances found that certain chemicals such as 2,4-D behave in
a similar manner. The application of 2,4-D to susceptible plants
stimulates abnormal growth, because the natural balance of
growth processes is distorted.
1Associate Agronomist, Agricultural Engineer and Interim Assistant
Horticulturist, respectively, Everglades Experiment Station, Belle Glade,
Florida.
U. S. Tariff Commission. Private communication dated June 13, 1952.






Florida Agricultural Experiment Stations


One of the first symptoms of a lethal application of 2,4-D to
susceptible plants is a curving of the younger plant stems and
leaf petioles. This condition is evident a few hours after spray-
ing and becomes very pronounced in two to three days. About
a week after treatment plants may have a wilted and chlorotic
appearance, while the young developing leaves tend to become
narrow, mottled and thickened. These effects may become pro-
gressively worse until the plant dies. If the concentration of
2,4-D spray is not lethal, partial recovery may take place from
any of the conditions mentioned above.
Susceptible plants are killed in one to four weeks after treat-
ment with 2,4-D. The quantity of the herbicide required to
kill different species of plants varies considerably. However,
one pound of 2,4-D acid equivalent per acre is generally suffi-
cient for practical control of susceptible weeds. The differential
response of various species of crop plants and weeds to treat-
ment with 2,4-D represents a property known as selectivity,
which makes it possible to control susceptible weeds in resistant
crops. Many important crops such as corn, sugar cane, pasture
grasses and rice, which are members of the grass family, are
either not affected or very little damaged by treatment with
2,4-D, and susceptible weeds in these crops can be controlled
with the herbicide. On the other hand, most vegetable crops,
such as tomatoes, beans, peppers and cabbage, are very suscep-
tible and 2,4-D cannot be used for weed control in these crops.

TYPES OF 2,4-D
There are several different chemical types of 2,4-D, but the
following are most widely used for weed control:
(1) sodium salt of 2,4-D.
(2) amine salts of 2,4-D (diethanolamine, triethanolamine,
isopropanolamine, morpholine, and dimethylamine).
(3) esters of 2,4-D.
(a) highly volatile types such as methyl, ethyl, isopropyl
and butyl esters.
(b) low volatile types such as the polyethylene glycol
derivatives of 2,4-D.
The sodium salt of 2,4-D is available as a solid and the amine
salts and esters as liquids. All types can be mixed with water
to obtain a spray solution. Some formulations of the sodium






2,4-D for Post-Emergence Weed Control


salt do not go into solution very rapidly; these types must be
dissolved before use.
The principal chemical types of 2,4-D are listed above in an
order related to their herbicidal properties. The sodium salt
is least effective on hard-to-kill weeds, the amine salts are
intermediate and the esters are most effective. Many of the
2,4-D esters are highly volatile; their use is not recommended
unless the area to be sprayed is located at a considerable dis-
tance from sensitive crops and great care is exercised in hand-
ling this type of 2,4-D. New ester formulations, polyethylene
glycol derivatives of 2,4-D, are now available commercially.
These herbicides have low volatility, but precautionary measures
should still be taken in their use. The amine and sodium salts
are safer to handle and the amine salts, especially, have given
satisfactory control of weeds.
Dust formulations of 2,4-D also are available. Tests have
shown that 2,4-D dusts are less effective for weed control and
more hazardous to susceptible crops than sprays. Their use is
not recommended.

2,4-D ACID CONTENT
Commercial formulations of 2,4-D contain varying quantities
of the active ingredient, 2,4-D acid, combined in different chemi-
cal forms. The higher the 2,4-D acid content of the formula-
tion the stronger the killing effect will be. Consequently, spray
solutions should always be made up on the basis of the actual
2,4-D acid equivalent content. The percent 2,4-D acid content
is generally stated on the label of the container and, with liquid
preparations, the number of pounds of 2,4-D acid equivalent
contained in one gallon of solution also is given. Recommenda-
tions for the use of 2,4-D are stated in terms of pounds of 2,4-D
acid equivalent per acre. The quantity of the commercial
formulation (sodium salt, amine salt or ester) that will furnish
the recommended amount of 2,4-D acid equivalent can be deter-
mined by relatively simple calculations.
Example.-The label on a container might give the following
information:

Alkanolamine salt of 2,4-D ..................................... 65%
Inert ingredients .............--......---........ ...----........... 35%
Total ......................... ..... .......... ............... ... ------100%

2,4-D acid equivalent is 39% or 4 pounds in one gallon.







8 Florida Agricultural Experiment Stations

The quantity of the above formulation on a volume or weight
basis that will furnish 1 pound 2,4-D acid equivalent per acre
is determined as follows:


(1) Volume
Pounds 2,4-D acid equivalent per acre
Pounds 2-4-D acid equivalent per gallon


= 14 = 0.25 gallons


(2) Weight
Pounds 2,4-D acid equivalent per acre X 100 Ix 100
2.56 pounds
Percent 2,4-D acid equivalent 39

WEEDS THAT CAN BE CONTROLLED

Tests with herbicides at the Everglades Station have shown
that a large number of the broadleaf weeds commonly found
in the Everglades can be controlled by spraying with 2,4-D.
However, a number of broadleaf weeds and most grass weeds
are not affected by treatment with the herbicide.
A list of some common weeds grouped according to their sus-
ceptibility to treatment with 2,4-D is given below.

SUSCEPTIBLE


Common Name
Match weed ............................
Wandering jew .......... .......
Mexican tea weed ...............
Spanish needle ............................
Water hyacinth .......................
Marsh flebane ........ .............
Rag weed ............................
Sticker weed .......................
Pigweed, "careless" weed ..........
Ground cherry ........................
......... ........ ... ..........
-........................................


Scientific Name
Phyla nodiflora (L.) Greene
Commelina diffusa L.
Ambrina ambrosioides (L.) Spach.
Bidens pilosa L.
Eichhornia crassipes Solms.
Pluchea pururrascens (SW.) DC
Ambrosia bidentata Michx.
Amaranthus spinosus L.
Acnida cannabina L.
Physalis pubeseens L.
Geranium carolinianum L.
Eclipta alba (L.) Hassk.


INTERMEDIATE


Common Name
D og fennel ...............................
Sow thistle -................... .......
False bishop weed ...............
Everglades boneset ..............
V ervain .............. .. ...... ...............
Burn or fireweed ....................
Iron or teaweed ....................
Nut grass ................. .........
Purslane ..................... ...............
.... ... ... ... .


Scientific Name
Eupatorium capillifolium (Lam.) Small.
Sonchus asper (L.) All.
Ptilimnium capillaceum (Michx.) Raf.
Eupatorium serotinum Michx.
Verbena scabra Vahl.
Erechtites hieracifolia (L.) Raf.
Sida carpinifolia L.
Cyperus rotundus L.
Portulaca oleracea L.
Erigeron quercifolius Lam.
Verbena urticaefolia L.







2,4-D for Post-Emergence Weed Control


LESS SUSCEPTIBLE
Common Name Scientific Name
Cressleaf groundsel ............-.. Senecio lobatus Pers.
Black nightshade .................. Solanum gracile Link.
Lantana .................... ....... Lantana camera L.
Elder ................................ Sambucus simpsonii Rehder
Dock ..................................... Rumex floridanus Meisn.
Sedge .................-.....- ...- Kyllingia brevifolia L.
Ponyfoot .............................. Dichondra carolinensis Michx.
.-.. .. ............. ............. Bramia monnieri (L.) Ritch.
RESISTANT
Common Name Scientific Name
Para grass ...................... Panicum purpurascens Raddi.
Napier grass ...... ..... ............ Pennisetum purpureum Schumach.
Bermuda grass ...-............. Cynodon dactylon (L.) Pers.
Pellitory, chick or artillery
weed .......-...... ................ Parietaria numularia Small.
Cudweed .................................. Gnaphalium spathulatum Lam.

The quantity and distribution of susceptible and resistant
weeds in the area to be treated will determine whether it is
practical to use 2,4-D or some other method of weed control.
Some partially resistant weeds are killed when sprayed in the
seedling stage with 2,4-D, and treatment at a later stage of
development may render the seed of other resistant types non-
viable.
In many cases the most effective control of weeds is obtained
by a combination of mechanical and chemical methods. For
example, with row crops mechanical cultivation can be used to
control weeds between the rows and treatment with 2,4-D to
kill weeds within the rows.

RATE OF APPLICATION
The quantity of 2,4-D that is essential for weed control will
vary from 0.5 to 2 pounds or even more of 2,4-D acid equivalent
per acre, but an application of 1 pound of 2,4-D acid equivalent
per acre is usually sufficient for average conditions.
Important factors controlling the rate of application of 2,4-D
are:
(1) Tolerance of the crop.
(2) Stage of growth of the crop as related to sensitivity.
(3) Susceptibility of the weeds.
(4) Age, density and condition of growth of the weeds.
(5) Level of soil fertility.
(6) Chemical type of 2,4-D used.
(7) Effects of rainfall and temperature.






Florida Agricultural Experiment Stations


The most important factor to be considered is whether the
crop is tolerant to treatment with 2,4-D. Some slightly suscep-
tible crops are less sensitive to 2,4-D at certain stages of growth.
Sugar cane does not appear to be affected when treated with
1 pound of 2,4-D acid equivalent per acre at any stage of its
growth. On the other hand, some varieties of corn will be in-
jured if sprayed with the same quantity of 2,4-D acid after 3
inches in height or during the period of tasselingg."
Susceptible weeds can be controlled with lesser quantities of
2,4-D than more resistant types. Plants with broad leaves are
relatively easier to kill than those with narrow leaves; although
there are many exceptions to this statement.
Young weeds can be killed with much smaller quantities of
2,4-D than mature weeds. Heavy stands of weeds require high-
er rates of application than light stands. It is generally im-
practical to attempt the control of very heavy mature stands
of weeds with 2,4-D; in such cases best results can be obtained
with mechanical methods.
Weeds growing rapidly on soils of high fertility are killed
more easily than when growing slowly under unfavorable con-
ditions.
The chemical types of 2,4-D differ in herbicidal effect. In
comparison with the amine salts, larger quantities of the sodium
salt and lesser quantities of the ester should be used.
The effect of 2,4-D treatment is sometimes reduced by heavy
rain falling two to three hours after spraying. However, the
losses' due to the washing effects of the rain can be reduced
by the addition of spreaders and stickers to 2,4-D sprays. A
better kill is generally obtained when air temperature is high.
Water is generally used as a diluent for 2,4-D sprays, but
diesel oil and other petroleum products also can be used for
the low gallonage application of the esters of 2,4-D. The sodium
and amine salts and esters of 2,4-D can be mixed with water,
but only the esters are miscible with oil.
The quantity of water that should be used with 2,4-D sprays
to obtain the most satisfactory herbicidal results will vary with
the crop to be treated, the susceptibility and stage of develop-
ment of the weeds, and the spray equipment available for use.
Rates of spraying for weed control are shown below:
(1) low gallonage rate, 2 to 10 gallons per acre.
(2) intermediate gallonage rate, 25 to 75 gallons per acre.
(3) high gallonage rate, 100 to 300 gallons per acre.







2,4-D for Post-Emergence Weed Control


The intermediate gallonage rate is most suitable for general
weed control operations. The low gallonage rate has the ad-
vantage that the cost of the equipment and of the application
of the spray liquid is considerably less than with the higher
rates. On the other hand, with this type of spraying opera-
tional stoppages caused by the clogging of the small nozzle
orifices take place more frequently. The high gallonage rates
can be used to best advantage to provide adequate coverage for
a very heavy growth of weeds.

USE OF 2,4-D IN CERTAIN TOLERANT CROPS
Post-emergence control of weeds with sprays of amine and
sodium salts of 2,4-D may be accomplished in certain tolerant
crops-which are mainly members of the grass family-on the
organic soils of the Everglades. Recommended rates of appli-
cation are given in terms of 2,4-D acid equivalent per acre.
When the herbicide is applied as a band over the row, suitable
adjustments in rate should be made.
Patures and Turf.-The need for weed control in pastures in
the Everglades is greatest in the early stages of establishment,
but at that time injury to the grass may occur if heavy applica-
tions of the herbicide are made.
Germinating seed of some species of grass can be killed or
severely damaged by spraying with 2,4-D. Grass seedlings and
young growth from recently planted cuttings also are some-
what sensitive and can be injured by treatment. However,
when the grass is three to six inches in height, an application
of 0.5 to 1 pound of 2,4-D acid equivalent per acre will cause
little or no injury to most species.
Well established stands of pasture grasses, such as St. Aug-
ustine grass (Stenotaphrum secundatum (Walt.) Kuntze.), Pan-
gola grass (Digitaria decumbens Stent.), Bermuda grass
(Cynodon dactylon (L.) Pers.), Para grass (Panicum purpur-
ascens Raddi.) and Carib grass (Eriochloa polystachaya H.B.K.),
which are commonly grown in the Everglades, can be safely
treated with 1 to 1.5 pounds 2,4-D acid equivalent per acre for
the control of broadleaf weeds. In such cases the most suitable
rate of application is mainly determined by the susceptibility
of the weeds to be controlled. Undesirable grassy weeds that
sometimes develop in pastures are not killed by treatment. It
may be more practical to control weeds in established pastures







Florida Agricultural Experiment Stations


under good management by regular mowing and proper fer-
tilizing than by the use of 2,4-D.
When legumes are grown in association with pasture grasses
it is not generally advisable to use 2,4-D for weed control, be-
cause many legumes can be severely injured.
Grasses sprayed with 2,4-D are not injurious to livestock and
the herbicide can be safely handled by humans.
Oats grown for supplementary winter pasture should not
be sprayed with 2,4-D in the seedling, booting or flowering
stages. Varieties of oats differ in their susceptibility to 2,4-D,
and preliminary tests should be run before large scale applica-
tions are made.
Turf grasses are affected by 2,4-D in a manner similar to
pasture grasses. They are most susceptible to injury when
treated in the young seedling stage or soon after close mowing.
Bent grasses (Agrostis spp.) can be injured by the herbicide,
especially when mowed frequently on golf greens, and only
light applications should be made.
Weedy areas in turf should be replanted and fertilized after
treatment with 2,4-D, so that a weed-free stand of grass can
be obtained.
When sensitive ornamental plants are growing in the vicinity
of lawns, golf greens or playgrounds, 2,4-D should be applied
to these areas in such a manner as to avoid injury.
Corn.-Field corn is not as susceptible to the effects of 2,4-D
as some sweet corn hybrids. It is not generally advisable to
apply more than 0.5 pound of 2,4-D acid equivalent per acre
to sweet corn for weed control, and the herbicide should not be
used if there is any doubt concerning the susceptibility of the
variety. Field corn can generally be treated with 0.5 to 1.0 pound
2,4-D acid equivalent per acre with little or no injury. Sprays
should be applied whenever possible beneath the leaf canopy
of the plants. This can be done by mounting the nozzles on
extension leads at a level lower than the boom.
The stage of development of the corn should be considered
before applying 2,4-D. Sweet corn can usually be sprayed with
2,4-D until the plants are 3 inches tall. On the other hand,
it is generally safe to treat field corn until the plants are 12
inches tall; some injury may occur if the herbicide is applied
when the plants are 12 to 24 inches tall. After that stage of
development the spray should not be applied to the tops of the







2,4-D for Post-Emergence Weed Control


plants. Corn should not be treated with 2,4-D just before or
during tasselingg."
When 2,4-D is improperly applied to corn the effects are as
follows: (a) The young plants bend to the ground. This con-
dition generally arises when 2,4-D is used at higher rates than
are recommended and may persist for two weeks before re-
covery. (b) The stalks become brittle and are easily broken
off. In areas where high winds are prevalent severe damage
can be caused. (c) The upper leaves roll into a tube-like shape
sometimes referred to as "onion leaf". (d) There is abnormal
development of brace roots. Some of these symptoms are shown
in Figure 1.
In 1948 experimental plots of the Big Joe variety of field
corn were sprayed with the amine salt of 2,4-D at the rate of
0.25, 0.75 and 1.50 pounds of 2,4-D acid equivalent per acre
about 18 days after planting. The yield of corn from plots
treated with 1.5 pounds of 2,4-D acid was about 20 percent lower

Fig. 1.-Big Joe field corn damaged by spraying with the amine salt of
2,4-D at the rate of 2 pounds acid equivalent per acre. Stalks are brittle
and severely bent.






Florida Agricultural Experiment Stations


than the check plots, to which 2,4-D was not applied. The other
rates of 2,4-D treatment did not cause a decrease in yield. These
results emphasize the fact that 2,4-D should not be applied to
field corn at rates exceeding 1 pound of 2,4-D acid equivalent
per acre.
Sugar Cane.-Most varieties of sugar cane will tolerate high
rates of 2,4-D from an early stage of their development without
injury.
The sodium salt of 2,4-D has been used quite extensively
for the control of weeds in sugar cane in the Everglades. This
formulation has somewhat weaker herbicidal properties than
the other chemical types and has been applied at a rate of
about 3 pounds 2,4-D acid equivalent in 70 to 150 gallons of
water per acre without injury to the crop. The amine salt
can be used at a rate of 1 to 2 pounds of 2,4-D acid equivalent
in 30 to 60 gallons of water per acre.
Rice.-In the Everglades rice is flooded about two weeks after
emergence. It is not generally advisable to use 2,4-D as a pre-
flooding treatment for weed control, because the young rice
seedlings are very sensitive to the effects of the herbicide. After
flooding, when the plants are three to four weeks old, an appli-
cation of 0.5 to 1 pound of 2,4-D acid equivalent per acre can
generally be made for the control of broadleaf weeds without
injury to the rice.
Ramie.-Ramie plantings require several weedings before a
proper stand is established. This is generally done by mechani-
cal methods. Sometimes, however, a very weedy condition de-
velops from poor germination of the planting stock or other
causes. When this occurs the amine salt of 2,4-D can be applied
at the rate of 1 to 1.5 pounds of 2,4-D acid equivalent per acre
for the control of broadleaf weeds. Yield and quality of the
fiber do not appear to be detrimentally affected by the 2,4-D
treatment. The vegetative growth of the plant is retarded for
a short period but recovery is fairly rapid.

2,4-D DAMAGE TO SUSCEPTIBLE CROPS
When an area is sprayed with 2,4-D, susceptible crops in the
vicinity may be damaged by spray particles of 2,4-D carried by
wind or by volatile vapors given off from certain 2,4-D formu-
lations.







2,4-D for Post-Emergence Weed Control


Movement of 2,4-D particles by wind generally occurs at
time of spraying and has been the principal cause of damage
to susceptible crops in the Everglades. The stronger the wind
velocity and the finer the spray particles, the greater is the
possibility of damage by spray drift. The danger of such dam-
age can be reduced by the following means: (1) spray when
there is little or no wind; (2) use low pressure, about 30 pounds
per square inch, to avoid fine sub-division of spray particles;
and (3) operate the sprayer with nozzles placed as close as is
practical to the upper surface of the weeds to minimize the
undesirable influence of air currents.
Several cases of extensive damage by 2,4-D to susceptible
crops have been reported five miles or more from the point of
application. In most of these cases either dusts, ester spray
formulations, airplane application or combinations of these
factors were usually involved under windy conditions.
The volatility of 2,4-D can cause damage to susceptible crops
either at the time of spraying or shortly thereafter, and de-

Fig. 2.-Typical leaf malformation (left) of Tendergreen beans sprayed
with 2,4-D, as compared with normal leaf (right).











.I .. .






Florida Agricultural Experiment Stations


pends on the type of 2,4-D formulation used, the atmospheric
temperature and the wind velocity. Esters of 2,4-D give off
volatile vapors that are toxic to susceptible plants at tempera-
tures of 65 F. and over. In recent studies the amine salts
showed little or no volatility. The sodium salt is considered
non-volatile under most conditions.


I1oo p~D~m.


50 p.p.m.


Fig. 3.-Canker formation on stems of Copenhagen Market cabbage due
to application of 2,4-D.

When susceptible crops are growing in the near vicinity of
an area that is in need of weed control, under no circumstances
should 2,4-D be applied. However, when susceptible crops are
1/2 mile or more away, it is generally safe to apply the amine
or sodium-salts of 2,4-D, if there is little or no wind movement,
or if the wind is blowing in the opposite direction to the
susceptible crops.






2,4-D for Post-Emergence Weed Control


DIFFERENTIAL TOLERANCE OF CERTAIN
SUSCEPTIBLE CROPS TO 2,4-D
Preliminary greenhouse tests at the Everglades Station
showed that the application of concentrations of 1,000, 100,
50, 20, 10, 1, 0.1 and 0.01 ppm. of 2,4-D acid equivalent to the
roots of young seedlings of different types of plants was less
toxic than to the tops of the same plants. Average results of
both root and top applications of 2,4-D showed a decreasing order
of tolerance of the following plants: beans, celery, cabbage,








4













Check
Fig. 4.-Leaflets of Rutgers tomatoes damaged by 2,4-D (left);
normal leaf (right).







Florida Agricultural Experiment Stations


tomatoes, okra, kenaf and cotton. The plants damaged by 2,4-D
in these tests recovered after a month or more of retarded
growth when placed under good growing conditions. The effect
of ttreatment on yield and quality of the fruit was not deter-
mined.
With the exception of some sweet corn hybrids, practically
all of the vegetable crops grown commercially in the Everglades
are susceptible to damage by 2,4-D. The damage caused to
beans, cabbage and tomatoes is shown in Figures 2 to 4.

SUITABLE EQUIPMENT AND METHODS FOR THE
APPLICATION OF 2,4-D
Spraying with 2,4-D can be successfully done with the fol-
lowing types of equipment:
(1) Knapsack or other hand-operated sprayers.
(2) Small spray units driven by gasoline motor or other
power sources, frequently mounted on wheelbarrow
frames.
(3) Spray assembly mounted on and powered by a tractor or
pick-up truck.
(4) Sprayer mounted on a trailer which is drawn by a tractor.
(5) Specially designed self-propelled sprayers.
Examples of some of these types of spray equipment are
shown in Figures 6 to 10 and the basic elements of a power
spray unit in Figure 5.
Satisfactory results can be obtained with different types of
equipment and methods of application. With extensive spray-
ing it may be desirable to have a large capacity supply tank
follow the operations. When weed growth is irregular or is
located in rather inaccessible places a spray gun can be used
to good advantage. Several types of spray guns are available
with single or multiple nozzles.
A uniform distribution of 2,4-D spray is essential for effec-
tive weed control, although complete leaf coverage is not re-
quired as is the case with certain insecticides and fungicides.
The first step is to determine the amount of 2,4-D acid that
is needed for a good weed kill and the quantity of water in
which it should be applied for satisfactory coverage. These
two factors considered together represent the concentration of
the solution and have already been dealt with. The next step
is to determine the nozzle size and type that will distribute the







2,4-D for Post-Emergence Weed Control


J.Tu^/ o// Presiure '








L0w PVESSU^F ,Sr'rT-ktT LAYYOu7-
Fig. 5.-Diagrammatic illustration of the basic elements of
spray unit.


a low-pressure


., 2




--





Vt ~


a-A v i


Fig. 6.-Low-cost portable sprayer developed at the Everglades
Experiment Station.


i.. -.-,...J.







V;

:







20 Florida Agricultural Experiment Stations

necessary amount of spray liquid at a practical forward speed
of the sprayer.
The most important components of the equipment, which
govern the discharge of the spray liquid from the machine,
are given below.
Nozzles.-Several different types of nozzles may be used, but
the fan-type ("fish tail") nozzle is used most extensively for
applying 2,4-D sprays. Some of the commercial types of "fish
tail" nozzles, with one type separated into its component parts
(body, strainer, cap and tip) are shown in Figure 11. Nozzles
are manufactured with great precision because their principal
function is to distribute the spray material uniformly.
Sprays with 2,4-D are generally applied in the form of rela-
tively coarse droplets so that the hazard of damage to suscep-
tible crops by spray drift can be reduced. Spray droplet size
is controlled by variations in nozzle orifice size and by adjust-
ments in pressure. A decrease in pressure causes an increase
in droplet size and lessens the chances of damage by spray

Fig. 7.-Spray equipment suitable for weed control in pastures. Note
simple boom assembly with nozzles directly attached. The pump is operated
from the fan shaft of the tractor and the spray liquid is carried in a tank
on the trailer cart.

.r .o .-


"- .
W,








it






2,4-D for Post-Emergence Weed Control


drift. A safe operating pressure is about 30 pounds per square
inch. Pressure also influences the angle of delivery and rate
of spray discharge. These effects are shown in Figure 12 for
several nozzles. This information was obtained from the Spray-
ing Systems Company and refers to the action of the "Teejet"
nozzles. Similar data are available for other manufacturers'
products.
The serial number of a "Teejet" nozzle is based on its per-
formance with water at 70' F. applied under 40 pounds pres-
sure per square inch. The number 8001 nozzle under standard
conditions forms a spray delivery angle of 800 and delivers 0.1
gallon of spray per minute. Thus for this particular nozzle the
first two digits of the number 8001 represent the angle and the
last two digits the rate of discharge. These characteristics of
the number 8001 nozzle will vary with other pressures. For
example, at 10 pounds pressure per square inch, the discharge
rate is 0.05 gallons per minute, while at 400 pounds it is in-
creased to 0.32 gallons per minute. In the above range of

Fig. 8.-The Everglades Mule equipped for weed control work. Booms
are folded for transport and storage. (Construction of this sprayer was
made possible by the generosity of Mr. Henry I. Cohn, Indian Trail Ranch,
Loxahatchee, Fla.)





...V __ -\ ,?
"." -: :




































Fig. 9.-High-clearance tractor used for spraying 2,4-D in sugar cane.
(Photograph courtesy U. S. Sugar Corporation, Clewiston, Fla.)



Fig. 10.-Spray unit with special boom assembly. Nozzles are mounted
on sled runners to maintain a uniform height of spray application on un-
even ground.












i ..- .

,I.
V-~ ~ 7i~L

I~a; ;-~t i-


rir


c-






2,4-D for Post-Emergence Weed Control


pressures the spray delivery angle of this nozzle will vary
from 52 to 94 degrees.


Fig. 11.-Commercial types of fish-tail nozzles. Principal parts of one
nozzle are shown at right.

The factors influencing the height at which the nozzles
should be placed above the tops of the weeds are illustrated
in Figure 13A. The four nozzles described in Figure 12, with
angles of spray delivery of 650, 800, 950 and 110" at 40 pounds
pressure per square inch, will cover a swath of 25.5, 33.6, 43.7
and 57.1 inches, respectively, when the nozzle is located 20
inches above the tops of the weeds. High nozzle placement may
allow an undesirable modification of the spray pattern by wind.






24 Florida Agricultural Experiment Stations





120















500---/ ----'---- --t--.6







40 .0.5
s o
















0.2,
50 --- ^0.4 ..















0.1 z


0 25 50 75 100 125 150 175 200
Pressure (Pounds per Square Inch)

Fig. 12.-Relationship between pressure and spray delivery angle (upper
diagram) and pressure and rate of spray discharge (lower diagram) for
four types of nozzle. Note that both spray delivery angle and discharge
increase with pressure. (Data based on drawing No. 2851, Spraying
Systems Co.)






2,4-D for Post-Emergence Weed Control


Rotation of the nozzle tip produces changes in the effective
spray width of the individual nozzles. Various angles of rota-
tion between 0 and 900 will give different widths of spray cov-
erage shown in Figure 13B. Thus spray patterns illustrated in
Figure 13C can be adjusted to avoid undue overlapping or in-
terference.
The use of special nozzles is sometimes necessary. "Off-
center" nozzles can spray a considerable distance on one side.
A cluster or multiple assembly of "off-center" nozzles, shown
in Figure 14, can be effectively used for the application of herbi-
cides in pastures.


A6_ ^ /


A-Sproy Pattern Width of 4 Nozzles 20 Inches From Orifice


B-Effective Pattern Widths with 3 Nozzle Settings


C--Nozles Set at Angle to Fill Pattern Without Interference
Fig. 13.-Spray coverage pattern in relation to spray angle, height and
rotation of nozzle tip.
























































o


- C



ZCD


E-4---]--- 40--- -" ----- ,- ^ ___

S-40












-4 /



I 10 _--
-_ -to _

^ i ___----_ _-


10 20 30 40 50 60

Pressure (Pounds per Square Inch)
Fig. 14.-Cluster nozzle assembly and diagram showing discharge and
coverage in relation to pressure from series -10 and -40 nozzles. (Data
based on drawing No. 5430, Spraying Systems Co.)


Y






2,4-D for Post-Emergence Weed Control


It is a good practice for the spray operator to have an extra
supply of nozzle tips and screens, so that little time is lost when
clogging of the nozzles occurs or when making check calibra-
tions of spray delivery.
Booms.-Spraying for weed control covers a wide range of
conditions and no standard boom design can be recommended.
Booms may be inexpensively constructed of galvanized pipe or
steel tubing with the nozzles mounted directly by drilling and
threading or attached to standard pipe fittings. The lateral
location of the nozzles on the boom is usually determined by
the row spacing of the crop to be treated. Figures 12 and 13
indicate that nozzles with a spray angle of 650 mounted 18
inches apart and located 20 inches above the top of the weeds
will be suitable for spraying a crop planted in 36-inch rows.
If the crop and weeds are about equal in height, the nozzles
can be directly attached to the boom. On the other hand, a
low weed growth in a tall crop will require a high placement
of the boom with the nozzles mounted at a lower level. With
different row spacings, changes have to be made in the nozzle
spacing on the boom and in the selection of nozzles with more
suitable spray delivery angles.
The boom can be connected to the spray delivery pump with
garden hose made of new types of synthetic materials, which
are not affected by the action of 2,4-D spray liquids.
Short booms distribute the spray liquid more uniformly on
uneven ground and cause less vibrational strain and pipe fric-
tion., Long booms should be built in sections so they can be
folded for transport and storage.
The length and size of the pipe and hose and the number and
type of fittings used in the assembly influence the pressure and
flow of the spray liquid. Figure 15 shows the pressure that
must be applied for each 100-foot section of standard galvanized
pipe of different sizes to obtain the indicated rates of liquid flow.
Any fraction of this length of pipe requires proportionally less
pressure.
Pumps.-Special high cost piston pumps are not needed for
applying 2,4-D sprays. Simple types of rotary pumps can be
used satisfactorily, providing the capacity is adequate. This
requirement is different from some other agricultural spray
operations. The capacity of the pump is mainly dependent on
size and speed of operation, and can be determined from maker's
specifications. The pump must have the capacity to deliver






Florida Agricultural Experiment Stations


the necessary quantity of liquid to the nozzles under a constant
pressure of about 30 pounds per square inch for uniform dis-
tribution of the spray.

5 0 T ---- f------ r- --- ---- .
I OOI










Gallons per Minute
4S J /


and rate of spray delivery. (D.ta based on Lea Formula, pp. 181 and
S 0 ~ -+. -- -- -- -
30i

C


a-


Io

0
0 2 4 6 8 10 12 14
Gallons per Minute
Fig. 15.-Effect of size of pipe per 100-foot section on pressure loss
and rate of spray delivery. (Data based on Lea Formula, pp. 181 and
206, Handbook of Hydraulics by Horace Williams King, McGraw-Hill,
1939.)

A pressure gauge should be installed as close as possible to
the point of spray discharge so that accurate pressure readings
can be obtained at all times. Pressure control on some pumps
is obtained by an integral pressure regulator, while other types
require an auxiliary regulator, the by-pass of which goes back
into the supply tank and produces a certain amount of agita-
tion. This is generally adequate for 2,4-D spray mixtures.
Quick action starting and stopping of the spray delivery is
controlled by a shut-off valve. A syphon valve used in combina-
tion with the shut-off valve makes this action more sensitive.
Check valves mounted between the boom and each nozzle pro-
duce a further refinement in this action and also prevent nozzle
drip.
Screens.-A source of clean water, free from suspended solids,
and proper screening of the 2,4-D spray solution are necessary for






2,4-D for Post-Emergence Weed Control


uninterrupted operation of the spray machine. Otherwise, a
considerable amount of time will be lost by frequent stoppages
due to clogging of the screens and nozzle orifices. With low
and intermediate rates of spraying, screens of fine mesh and
nozzles of small orifice size are generally used; 2,4-D spray
solutions which are apparently clean may contain fine particles
that will quickly clog these parts of the spray system.


Acres per Hour
Fig. 16.-Acreage sprayed per hour in relation to speed and working width
of the implements.

A screen should be placed in the outlet line of the spray sup-
ply tank, and in the inlet line also, if the source of water is not
clean. A large capacity screen should be installed on the suction
line to the pump. Multiple part nozzles are provided with
screens as a part of the assembly. The mesh of the screen is
about the size of the nozzle orifice. Large spray rigs should
have in-line screens in each section of the boom.







Florida Agricultural Experiment Stations


PRACTICAL ASPECTS OF FIELD APPLICATION OF 2,4-D
Several factors must be considered in the operation of equip-
ment for applying 2,4-D. With different conditions of spray-
ing and types of equipment, many of these factors are more or
less fixed and cannot be easily adjusted. For example, nozzle
spacing on the boom should conform with the row spacing of
the crop to be treated; size and type of sprayer limits the scope
of certain operations, and so forth. On the other hand, there
are other factors-such as concentration of the spray solution,
rate of nozzle discharge and ground speed of the sprayer-that
can be controlled by the operator.
The widest variation of 2,4-D application can be obtained by
changing the concentration of the spray solution. Herbicidal
properties of spray solutions of different concentrations will not
vary to any great extent if the same quantity of 2,4-D acid is
applied per acre.
Another means of controlling 2,4-D application is by modify-
ing the rate of spray discharge by the use of different size
nozzles. This adjustment is limited to the rate of spraying
that is most suitable for a given set of conditions. For instance,
intermediate gallonage rates would be limited to adjustment
within the range of 25 to 75 gallons per acre.
Rates of 2,4-D application can be adjusted to some extent
also by varying the speed of the sprayer. Speeds can be varied
from two to five miles per hour. However, for most economical
operation, speed should be maintained at as high a rate as is
practical under existing field conditions. A frequent check of
speed should be made by a speedometer mounted on the tractor
or by test runs. The speed of travel multiplied by the width
of the strip sprayed or "swath" gives a rate of land coverage.
This can also be determined by reference to Figure 16 if the
speed and swath width are known.

PRECAUTIONS TO BE TAKEN IN THE USE OF 2,4-D
Set aside a sprayer for use only with 2,4-D, because it is very
difficult to remove traces of the herbicide from spray equipment.
Read carefully the instructions on the label of the 2,4-D con-
tainer.
Apply 2,4-D sprays with suitable types of ground equipment.







Florida Agricultural Experiment Stations


PRACTICAL ASPECTS OF FIELD APPLICATION OF 2,4-D
Several factors must be considered in the operation of equip-
ment for applying 2,4-D. With different conditions of spray-
ing and types of equipment, many of these factors are more or
less fixed and cannot be easily adjusted. For example, nozzle
spacing on the boom should conform with the row spacing of
the crop to be treated; size and type of sprayer limits the scope
of certain operations, and so forth. On the other hand, there
are other factors-such as concentration of the spray solution,
rate of nozzle discharge and ground speed of the sprayer-that
can be controlled by the operator.
The widest variation of 2,4-D application can be obtained by
changing the concentration of the spray solution. Herbicidal
properties of spray solutions of different concentrations will not
vary to any great extent if the same quantity of 2,4-D acid is
applied per acre.
Another means of controlling 2,4-D application is by modify-
ing the rate of spray discharge by the use of different size
nozzles. This adjustment is limited to the rate of spraying
that is most suitable for a given set of conditions. For instance,
intermediate gallonage rates would be limited to adjustment
within the range of 25 to 75 gallons per acre.
Rates of 2,4-D application can be adjusted to some extent
also by varying the speed of the sprayer. Speeds can be varied
from two to five miles per hour. However, for most economical
operation, speed should be maintained at as high a rate as is
practical under existing field conditions. A frequent check of
speed should be made by a speedometer mounted on the tractor
or by test runs. The speed of travel multiplied by the width
of the strip sprayed or "swath" gives a rate of land coverage.
This can also be determined by reference to Figure 16 if the
speed and swath width are known.

PRECAUTIONS TO BE TAKEN IN THE USE OF 2,4-D
Set aside a sprayer for use only with 2,4-D, because it is very
difficult to remove traces of the herbicide from spray equipment.
Read carefully the instructions on the label of the 2,4-D con-
tainer.
Apply 2,4-D sprays with suitable types of ground equipment.







2,4-D for Post-Emergence Weed Control


Operate the spray machine, whenever possible, at a pressure
of about 30 pounds per square inch to reduce danger of spray
drift.
The amine and sodium salts of 2,4-D are recommended for
general weed control operations. Do not use 2,4-D dusts and
avoid the use of 2,4-D esters.
Do not apply 2,4-D when heavy rains are expected.
Do not use 2,4-D when susceptible crops are growing close
to the area to be treated. However, when susceptible crops
are located 1/2 mile or more away, it is generally safe to use
the amine or sodium salt formulations if there is no wind or
if the wind is blowing in the direction opposite to these crops.
Do not spray more than 100 acres per day in the same lo-
cality.
Do not store 2,4-D in the same building with seeds, fertilizers,
insecticides or fungicides.
Do not apply 2,4-D at higher rates than are recommended
for weed control in a given crop.
When in doubt concerning the proper manner of using 2,4-D,
consult a county agricultural agent or qualified experiment sta-
tion worker.

SUMMARY

Experimental work with 2,4-D for controlling weeds in pas-
tures, turf and certain field crops has been in progress at the
Everglades Experiment Station for several years. This work
has shown the advantages of using 2,4-D for the control of
susceptible broadleaf weeds.
Improper use of 2,4-D in the Florida Everglades and else-
where has been the cause of a considerable amount of damage
to sensitive vegetable crops. This bulletin outlines methods
for the safe use of 2,4-D.
Some of the more common weeds in the Everglades are listed
according to their susceptibility to treatment with 2,4-D.
A list of the principal chemical types of 2,4-D is given. The
quantity of the herbicide that will be required for the control
of weeds will vary considerably, but one pound of 2,4-D acid
equivalent per acre usually is sufficient for average conditions.
Rates of 2,4-D spray application with ground equipment are
discussed. Intermediate rates with 25 to 75 gallons of water
per acre are most commonly used.







Florida Agricultural Experiment Stations


Various types of equipment and conditions suitable for apply-
ing 2,4-D are presented. A detailed account is given of the
functions of the important components of the spray machine,
namely nozzles, booms, pumps and screens.
Factors affecting the successful operation of spray equipment
are reviewed.
Precautions that should be taken in the proper use of 2,4-D
are listed.
Several equations which may be useful in the application of
2,4-D under controlled conditions are presented. Examples are
given to illustrate the use of the equations.

ACKNOWLEDGMENTS
The authors wish to express their appreciation to the management of
the United States Sugar Corporation, Clewiston, Florida, whose grant-in-
aid facilitated the progress of certain phases of the work reported in this
publication.
Different types of 2,4-D used in weed control tests were supplied by the
following manufacturers: The Dow Chemical Company, American Chemi-
cal Paint Company, E.I. Dupont de Nemours and Company, Pennsylvania
Salt Manufacturing Company, and Michigan Chemical Corporation.
Acknowledgment is made to Grant Averill for the photographic work,
to E. King and E. M. Dull for making the diagrams, and to Bill Desnoyers,
deceased, formerly Assistant Agricultural Engineer, for assisting with
certain phases of the weed control work.



It is necessary in a publication of this nature to make mention of trade
names of certain products and equipment. However, no endorsement of
the products named is intended, nor is criticism implied for similar products
which are not mentioned.







2,4-D for Post-Emergence Weed Control


APPENDIX

The following equations can be used to determine certain
values that are useful in the application of 2,4-D under con-
trolled conditions:


(1) Miles per hour


(2) Acres per
spray tank


(3) Spray time
minutes per acre


(4) Spray rate
gallons per
minute

(5) Spray rate
gallons per
minute

(6) 2,4-D acid
equivalent per
acre

(7) 2,4-D formulation
pounds or gallons
per spray tank


(8) 2,4-D formulation
pounds or gallons
per spray tank

(9) 2,4-D formulation


spray tank X spr
gallons fee


test run in feet

time in minutes X 88

spray tank, gallons

Spray rate, gallons per acre

43,560

spray swath, X speed X 88
feet mph

spray rate, gallons per acre

spray time, minutes per acre

acres per hour X gallons per acre

60

2,4-D acid equiv. content of the formulation

acres sprayed per pound or gallon of 2,4-D
formulation

acres per spray tank

acres sprayed per pound or gallon of 2,4-D
formulation


spray tank
gallons

spray rate
gallons per acre


2,4-D acid equiv.
pounds per acre
X
2,4-D acid equiv.
content of the formulation


pounds or gallons per spray tank =
2,4-D acid
ay swath X speed X equiv. pounds
t mph per acre


number of
X nozzles


2,4-D acid
X equiv. content
of formulation


The use of these equations is illustrated in four examples.
In these examples the following conditions are held constant:
(1) the spray boom is made up of 12 nozzles spaced 18 inches
apart covering a spray swath of 18 feet; (2) the spray tank
has a capacity of 200 gallons; (3) the commercial formulation
of 2,4-D contains 3.65 pounds 2,4-D acid equivalent per gallon;


spray rate
gals. per min.
per nozzle


X 495


__






Florida Agricultural Experiment Stations


(4) 1 pound of 2,4-D acid equivalent is applied per acre; (5)
the operating pressure is maintained at 30 pounds per square
inch.
EXAMPLE 1
Object.-to determine the speed of travel of the sprayer.
A test run shows that the sprayer travels 1,000 feet in 3.27
minutes. By applying the calculations in equation (1) the speed
of travel is
1,000 1,000
= -- 3.47 miles per hour
3.27 X 88 287.76

EXAMPLE 2
Object.-To determine the number of gallons of the com-
mercial formulation of 2,4-D that should be added to the spray
tank when the rate of application is 1 pound 2,4-D acid equiva-
lent in 40 gallons of water per acre.
The quantity of 2,4-D is determined by substituting in equa-
tion (8) the following known values: 200 gallon tank capacity;
40 gallons spray per acre; 1 pound 2,4-D equivalent applied per
acre; 3.65 pounds of 2,4-D acid equivalent per gallon of the
commercial formulation.
200 1 200
2,4-D formulation X = 1.37 gallons
gallons per spray tank 40 3.65 146

Let us assume that it may not be convenient to measure 1.37
gallons accurately, and suppose for convenience that we add
1.50 gallons to the spray tank instead. This quantity contains
1.50 X 3.65 = 5.48 pounds 2,4-D acid equivalent, and with an
application of 1 pound of 2,4-D acid equivalent per acre will
200
amount to -- = 36.5 gallons of spray per acre.
5.48
EXAMPLE 3
Object.-To determine the rate of nozzle discharge when
spraying 36.5 gallons per acre at a speed of 3.47 miles per hour.
The nozzle discharge can be found by the use of equation
(3) and the following calculations:
Spray time minutes per acre
43,560 43,560
46--- 4---- 7.9 minutes to spray an acre
18 X 3.47 X 88 5,496.48







2,4-D for Post-Emergence Weed Control


The spray discharge through the boom assembly of 12 nozzles
will be 36.5 7.9 = 4.62 gallons per minute. This will amount
to 4.62 12 = 0.385 gallons per minute per nozzle.
Referring to Figure 12, we find that a nozzle is not available
for this exact rate of spray delivery at an operating pressure
of 30 pounds per square inch. However, we could use an -04
nozzle that will deliver 0.35 gallons per minute at the required
pressure. But in order to offset the slightly lower rate of de-
livery of the -04 nozzle, we will have to decrease the speed of
the tractor. The slower speed can be determined as follows:
0.35 1.2145
X 3.47 3.15 miles per hour
0.385 0.385

It should be possible to obtain this speed by a minor throttle
adjustment.
EXAMPLE 4
Object.-To control spray delivery by variations in the rate
of nozzle discharge and the speed of the machine.
By substituting in equation (9) the known values (1.50 gallons
of commercial 2,4-D formulation added to spray tank; 200 gal-
lon capacity of spray tank; 18 feet width of boom; 1 pound
2,4-D acid equivalent per acre; 12 nozzles in the boom assembly;
3.65 pounds of 2,4-D acid equivalent in one gallon of the com-
mercial formulation; 495 a constant in the equation) we obtain
the following result:
200 X 18 X speed, mph X 1
1.5 =-
spray rate X 12 X 3.65 X 495
gals./min./nozzle
speed, mph
1.5 =--
6.0225 X spray rate
gals./min./nozzle

By transposing we can obtain two simplified equations which
can be used to determine: (a) the speed when the rate of spray
discharge through the nozzle is varied; and (b) the rate of spray
discharge when the speed is varied.

(a) speed, miles per hour = 9.03375 X spray rate-gals/min/nozzle
speed, miles per hour
(b) spray rate-gals/min/nozzle =-
9.03375






36 Florida Agricultural Experiment Stations

In order to illustrate the use of the equations, let us assume
that we wish to use an -03 nozzle which delivers 0.26 gallons
per minute per nozzle at 30 pounds pressure, then the speed of
the spray machine = 9.03375 X 0.26 = 2.35 miles per hour.
On the other hand, suppose we wish to operate the machine at
a speed of 3.15 miles per hour, then the rate of spray dis-
3.15
charge = 0.349 gallons per minute per nozzle. This
9.03375
rate can be obtained by the use of an -04 nozzle which is rated
to deliver 0.35 gallons per minute per nozzle at 30 pounds pres-
sure.




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