Group Title: Circular ;
Title: Guide for use of herbicides in Florida citrus /
CITATION THUMBNAILS PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00102057/00001
 Material Information
Title: Guide for use of herbicides in Florida citrus /
Series Title: Circular ;
Physical Description: 1 folded sheet (12 p.) : ill. ; 23 cm.
Language: English
Creator: Ryan, George F
Davis, Robert M
University of Florida -- Agricultural Extension Service
Publisher: Agricultural Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville, Fla
Gainesville, Fla
Publication Date: 1967
Copyright Date: 1967
 Subjects
Subject: Herbicides   ( lcsh )
Citrus -- Diseases and pests -- Control -- Florida   ( lcsh )
Weeds -- Control -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: George F. Ryan and Robert M. Davis.
General Note: Cover title.
General Note: "June 1967."
 Record Information
Bibliographic ID: UF00102057
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 213812709

Full Text
CIRCULAR 303 A
JUNE 1967









GUIDE FOR USE
OF HERBICIDES
IN FLORIDA CITRUS


AGRICULTURAL EXTENSION SERVICE
INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES
UNIVERSITY OF FLORIDA, GAINESVILLE






SUGGESTIONS FOR CHEMICAL WEED CONTROL
RATES GIVEN ARE FOR POUNDS OF ACTIVE INGREDIENT PER ACRE ACTUALLY SPRAYED
Rate per Time of Weeds
Situation Chemical Acre Application Controlled Remarks


6.4 to 9.6
lbs.


Bearing
groves































Planting sites
and non-crop
areas which
contain no
roots of
citrus trees











Grove ditches
(bottoms
only)








Grove ditches
(general)

















Citrus
Nurseries



Weed en-
croachment
barriers























Burrowing
nematode
buffer zones












Spot eradi-
cation of
torpedograss


In spring to
weed-free area


Young non-
bearing
groves


simazine







diuron






terbacil


paraquat






dalapon








diuron










simazine





terbacil




dalapon











2,4-D and/
or
2,4,5-T


diuron




monuron-
TCA




dalapon





2,4-D and/
or 2,4,5-T





silvex





dichlobenil




diuron









fenuron









fenuron-
TCA




diuron






monuron-
TCA





methyl
bromide





bromacil


3.2 to 6.4
Ibs.





3 to 4 lbs.






1 to 1 lbs.






3 applications
of 1.5 lbs. with
2- to 4-day
intervals





3.2 to 6.4
lbs.









6.4 to 9.6
lbs.




3 to 4 lbs.




2 applications
of 3.7 to 5.6
lbs. with a 5-
to 10-day in-
terval







2 to 4 lbs.




20 to 40 lbs.





22 to 44 lbs.




2 applications
of 3.7 to 5.6
lbs. with a 5-
to 10-day in-
terval

2 to 4 lbs.






4 lbs.





4 to 6 lbs.




20 to 40 lbs.









50 lbs.









100 lbs.





20 to 40 lbs.






33 to 44 lbs.






1-% to
4 Ibs. per
100 sq. ft.




24 lbs.


In spring to
weed-free area






Spring






Any time






In spring very
soon after grass
starts to grow
or very soon after
grass starts to
regrow following
mowing during
other times of
year

In spring to
weed-free area









In spring to
weed-free area





Spring




Any time when
grass is growing
vigorously









Any time when
weeds are grow-
ing vigorously


When ditches are
dry or contain
less than 2 inches
of standing water


When ditches
are dry or con-
tain less than
2 inches of
standing water

Any time weeds
are growing
vigorously



Any time weeds
are growing
vigorously




Any time weeds
are growing
vigorously



In spring to
weed-free area



Any time









Any time









Any time




After area
has been
fumigated
and leveled




After area
has been
fumigated
and leveled




Any time to
well-tilled
soil




Early spring
to mid-summer


All weeds Most effective when applied
to recently cleaned ditches.
Flush ditches well before
using water for irrigation or
spraying.

All weeds Most effective when applied
to recently cleaned ditches
Flush ditches well before
using water for irrigation or
spraying.

Perennial Keep spray drift off citrus
grasses and foliage and away from tree
cattails rooting zone. Use nonionic
wetting agent in spray solu-
tion.

Broadleaf Use amine salt forms. Keep
weeds, vines spray drift off citrus foliage
and brush and away from tree rooting
zone. If brush is tall, cut
off and treat sprouting
stumps. May be used with
first application of dalapon.

Broadleaf Keep spray drift off citrus
weeds, vines foliage and away from tree
and brush rooting zone. Not as effec-
tive against certain brush
species as 2,4,5-T.

Annual weeds Follow with 1%-1/ inch irri-
gation. Do not disturb soil
after treatment. Two appli-
cations per year if needed,
not less than 90 days apart.

All weeds, Do not use in areas where
including chemical may be leached into
torpedograss rooting zones of citrus or
other desirable plants. May
last 2 years or more. Not
to be used in an area in-
fested with torpedograss.
Serves as a barrier between
area infested with torpedo-
grass and clean area.

Torpedograss Do not use in areas where
chemical may be leached into
rooting zones of citrus or
other desirable plants. May
last up to 1 year. Not to be
used in an area infested with
torpedograss. Serves as a
barrier between area infest-
ed with torpedograss and
clean area.

Torpedograss Do not use in areas where
chemical may be leached in-
to rooting zones of citrus or
other desirable plants. May
last up to 1 year.

All weeds Use the higher rates if
perennial grasses are pres-
ent. Do not treat outside of
fumigated area. May last 2
years or more. Light discing
at 6-month intervals may in-
crease length of control.

All weeds Use the higher rates if
perennial grasses are pres-
ent. Do not treat outside of
fumigated area. May last up
to 2 years. Light discing
at 6-month intervals may in-
crease length of control.

Torpedograss If citrus trees present, re-
move carefully before treat-
ment. Keep gas sealed in
area 48 hours or more. Re-
planting of trees may be
done 7 to 10 days after treat-
ment.

Torpedograss Do not apply in root zone of
trees. Spot treatment of re-
maining live grass may be
necessary 4 to 6 months after
application. Trees may be
planted 1 year after initial
treatment.


Annual weeds
and perennial
weed seedlings





Annual weeds
and perennial
weed seedlings





Annual weeds
and perennial
grasses




Burndown of
all weeds





Perennial
grasses







Annual weeds
and perennial
weed seedlings









Annual weeds
and perennial
weed seedlings




Annual weeds
and perennial
grasses


Perennial
grasses (not
torpedograss)









Perennial,
broadleaf
weeds, vines
and brush


Do not apply in groves under
1 year from planting. Use
the higher rates in soils con-
taining more organic matter.
Use only 1 application per
year, or divide total amount
in 2 applications.

Do not apply in groves under
1 year from planting. Use
the higher rates in soils con-
taining more organic matter.
Use only 1 application per
year, or divide total amount
in 2 applications.

Do not apply in groves
younger than 2 years. Use the
higher rates in soils contain-
ing more organic matter. For
control of perennial grasses,
make a second application as
needed.

Avoid contact with citrus
foliage or green bark. Repeat
applications as needed. Use
non-ionic wetting agent in
spray solution. Observe label
precautions on use of protec-
tive clothing.

Do not apply in groves
younger than 4 years. Use
only 1 series of applications
per year. Use nonionic wet-
ting agent in spray solution.
Do not apply to bare soil
over tree root zone.



Use the higher rates in soils
containing more organic mat-
ter. May be used with the
first application of dalapon
treatment above for control
of paragrass and guineagrass
seedlings, but dalapon appli-
cation should be reduced
from 3 to 2 applications. Use
only 1 series of applications
per year.

Use the higher rates in soils
containing more organic mat-
ter. Use only 1 application
per year. May be used with
the first application of dala-
pon.

Use the higher rates in soils
containing organic matter.
For control of perennial
grasses, make a second appli-
cation as needed.

Repeated series of treat-
ments necessary for com-
plete elimination of grasses,
especially those which pro-
duce viable seed. Plowing
with moldboard turning plow
4 weeks after second appli-
cation aids kill. Citrus may
be planted 6 weeks after
second application. Use non-
ionic wetting agent in spray
solution.

May be included with first
dalapon application above.
Use amine salt form.






GUIDE FOR USE
OF HERBICIDES
IN FLORIDA CITRUS
George F. Ryan and Robert M. Davis'
This publication supersedes recommendations given in
Circular # 224, "Chemical Weed Control in Citrus Groves",
dated April 1962.

Weed control in citrus groves is a time consum-
ing and expensive operation. Cultivation by me-
chanical devices is not only expensive but also
inadequate, often causing serious root and trunk
damage. Proper application of herbicides can re-
sult in a more effective and economical means of
weed control.
TEN PRINCIPLES OF WEED CONTROL
1. Know the herbicide, its chemical proper-
ties, limitations and precautions.
READ THE LABEL!
2. Know the weed problem. Is it primarily
grasses, or is it broadleaf weeds? Are they
annuals or perennials? Certain herbicides
are effective only against certain kinds of
weeds.
3. Apply the proper rate. Excessive amounts
may interfere with herbicidal action, result-
ing in poor control and damage to the tree.
Too low a rate may not result in good weed
control.
4. Rates will vary with soil type. Crops grown
on soils containing higher amounts of or-
ganic matter will tolerate higher rates of
herbicides. Use lower rates on lighter soils
containing less organic matter. Higher rates
on lighter soils may damage the tree.
5. Apply at the proper time. Preemergence
type herbicides are more effective against
germinating weed seedlings than against
older plants. Growth regulator or hormone
type herbicides should be applied when
weeds are growing vigorously.
1Assistant Horticulturists, Florida Agricultural Ex-
periment Station and Florida Agricultural Extension
Service, respectively.






6. Apply when soil moisture is at the proper
level. Insufficient soil moisture will result
in poor weed control from preemergence
chemicals because they have to be in solu-
tion to control weed seedlings. Excessive
rainfall or irrigation soon after application
may leach the chemical out of the surface
of the soil or wash off foilage-absorbed ma-
terials.
7. Apply only to healthy, vigorous trees. Herbi-
cides may adversely affect trees in poor nu-
tritional condition, those damaged by cold,
drought, flooding or insects and diseases.
Generally, older trees will tolerate higher
rates than younger trees.
8. Do not cultivate after treatment unless spec-
ified on the label. Cultivation may destroy
the chemical layer and bring weed seeds to
the surface where they may germinate.
9. Do not apply under windy conditions. Spray
drift or vapors coming in contact with foli-
age may damage trees. When using 2,4-D
or 2,4,5-T, use only the amine salt form.
10. Use properly designed equipment in good
operating condition. Poorly designed equip-
ment may result in improper application
rates, incorrect placement of the herbicide,
damage to trees or poor weed control.

HERBICIDES
Bromacil.-A non-selective, root-absorbed, soil-
sterilant type herbicide; a preemergence herbi-
cide at low rates; also effective against some
established perennial grasses; available in wet-
table powder and granular form; essentially non-
corrosive to spray equipment and non-toxic to
warm-blooded animals; soil moisture necessary
for proper action; should not be used in tree root
zone.
Dalapon.-A leaf-absorbed, translocated herbi-
cide; selective against grasses; kills best when
applied to young, vigorously growing grasses;
should have at least four hours drying time before
rainfall; soluble in water but not in oil and is






somewhat corrosive to spray equipment; rela-
tively non-toxic to warm-blooded animals; has a
temporary stunting effect on citrus trees from
foliage or root absorption; should not be used in
groves under four years old.
Dichlobenil.-A non selective, root absorbed,
soil-sterilant type herbicide; a preemergence her-
bicide at low rates; available in wettable powder
or granular form; essentially non-corrosive to
spray equipment and non-toxic to warm-blooded
animals; soil moisture necessary for proper ac-
tion; effectiveness may be reduced unless applica-
tion is followed immediately by light irrigation
or rainfall or light mechanical incorporation.
Diuron.-A non-selective, root-absorbed, soil-
sterilant type herbicide; a preemergence herbi-
cide at low rates; available in wettable powder or
granular form; essentially non-corrosive to spray
equipment and non-toxic to warm-blooded ani-
mals; soil moisture necessary for proper action;
may cause a yellow-veining of citrus foliage from
root absorption; should not be used in groves less
than one year old.
Fenuron or FenuronTCA.-Non-selective, root-
absorbed, soil-sterilant type herbicides; very toxic
to all plants; relatively non-toxic to warm-blooded
animals; soil moisture necessary for proper ac-
tion; should not be used near citrus trees or other
desirable plants.
Methyl Bromide.-A non-selective soil fumi-
gant; toxic to all plants and most seeds; a gas
under normal pressure and temperature; requires
special application methods and equipment; must
be sealed in treated area with air-tight covering;
extremely toxic to warm-blooded animals; should
not be used near citrus trees.
MonuronTCA.-A non-selective, root-absorbed,
soil-sterilant type herbicide; toxic to most plants;
relatively non-toxic to warm-blooded animals; soil
moisture necessary for proper action; should not
be used near citrus trees or other desirable plants.

Paraquat.-A non-selective contact herbicide;
kills tops of sprayed weeds; periodic application
necessary to control new weed seedlings and re-






growth of perennial weeds; may be used in com-
bination with preemergence herbicides; somewhat
corrosive to spray equipment; moderately toxic
to warm-blooded animals; observe label precau-
tions on use of protective clothing; should be
kept off citrus foliage and green bark.

Silvex.-A leaf-absorbed, growth-regulator type
herbicide; effective against some species of broad-
leaf plants; relatively non-corrosive to spray
equipment; essentially non-toxic to warm-blooded
animals; herbicidal concentrations should be kept
off citrus foliage.

Simazine.-A non-selective, root-absorbed, soil-
sterilant type herbicide; a preemergence herbi-
cide at low rates; available in wettable powder or
granular form; essentially non-corrosive to spray
equipment and non-toxic to warm-blooded ani-
mals; soil moisture necessary for proper action;
should not be used in groves less than one year
old.

Terbacil.-A non-selective, root-absorbed, soil-
sterilant type herbicide; a preemergence herbi-
cide at low rates; also effective against some
established perennial grasses; essentially non-
corrosive to spray equipment and non-toxic to
warm-blooded animals; soil moisture necessary
for proper action; may cause temporary yellow
network of small veins on citrus foliage from root
uptake.

2,4-D. A growth-regulator type herbicide;
generally leaf absorbed; selective against broad-
leaf weeds; relatively non-corrosive to spray
equipment; essentially non-toxic to warm-blooded
animals; herbicidal concentrations should be kept
off citrus foliage and away from the tree root
zone; the amine salt form should be used to mini-
mize the possibility of vapor drift.

2,4,5-T.-Similar in action to 2,4-D but gen-
erally kills more woody plant species than 2,4-D;
also relatively non-corrosive to spray equipment
and non-toxic to warm-blooded animals; herbi-
cidal rates should be kept off tree foliage and
away from tree root zone; only the amine salt






form should be used near citrus trees or other
desirable plants.
EQUIPMENT
Equipment for herbicide applications need not
be expensive. Most herbicides are applied at low
pressure (20-50 pounds per square inch) and at
low volume. There is no need to purchase large
capacity, high volume systems. With certain
modifications, present sprayer systems can be
adapted for herbicidal applications.

A covered boom is desirable for spraying herbi-
cides to prevent wind drift, spraying of foliage
and interference of tree limbs.
A herbicide spray should have the following
features:
A metal or fiberglas tank which can easily
be cleaned. A wooden tank will absorb cer-
tain materials (i.e., 2,4-D or 2,4,5-T) pre-
venting its use for other materials or spray
operations.

A low pressure, low volume pump that is
relatively inexpensive and easily replaceable.
The pump should have a minimum capacity
of 4 gpm and should be resistant to the abra-
sive action of wettable powders.

The sprayer should have a provision for agi-
tation. Thorough agitation is necessary to
keep some herbicide materials in suspension.
Mechanical agitation generally will be more
satisfactory than a by-pass from the pump.

The spray boom should be adjustable in
height and be covered to prevent interfer-
ence with tree limbs. The boom height and
the nozzle spacing should allow a slight over-
lap of the spray pattern at ground level with
preemergence herbicides or at the top of the
weeds with postemergence applications.

A pressure regulator and accurate pressure
gauge should be located as near as possible
to the boom. This equipment plus a quick
opening and closing valve should be located
within easy reach of the operator.







Fifty-mesh screens should be included in the
intake line and nozzles. Screens finer than
fifty-mesh will not allow some wettable powd-
ers to pass through readily.

Nozzles should be of the flat-fan type with
a capacity of 0.2 to 0.6 gpm at a pressure of
40 psi.

Hand booms or guns can be used in ditches and
non-crop areas providing the pressure is low and
droplet size is large enough to prevent drift.

Gravity flow applicators are available for
either manual or tractor mounted operations in-
volving granular herbicides. This type of appli-
cator is usually more difficult to calibrate and to
spread the material uniformly because of humid-
ity, temperature, growth habit of the tree, and
nature and size of granules. The speed of the fan,
ground speed of the applicator, and area of
metering orifices will also affect uniformity of
distribution.

CALIBRATION

Proper calibration, either for sprayers or granu-
lar applicators, is essential for good weed control.
Space does not permit detailed description of
calibration of equipment. For details consult
Florida Agricultural Extension Circular 275A,
"Calibration of Pesticide Applicators", dated
September 1965.











FIG. 1-FLAT-FAN TYPE SPRAY NOZZLES
SHOWING PROPER OVERLAP.
COOPERATIVE EXTENSION WORK IN
AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Agricultural Extension Service, University of Florida
and
United States Department of Agriculture, Cooperating
M. O. Watkins, Director




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