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Everglades Station Mimeo Report EES65-21 March 1965
APPLY 2,4-D WITH CAR 4'
J. R. Orsenigo
Chlorophenoxy herbicide (2,4-D) injury to susceptible vegetable crops in
the Everglades farming area has increased greatly in recent years. Often,
damage was related to nearby sugarcane weed control operations. Poorly con-
trolled application of 2,4-D (and 2,4,5-T) is a direct hazard to many vegetable
The most common damage is visible; appearance, quality and yield of veget-
ables may be affected. Vegetables may also be contaminated with illegal-residues.
Many plants of urban areas; ornamentals, home gardens, nurseries and trees, are
susceptible to chlorophenoxy herbicides.
Positive determination of damage is not simple since diseases, insects,
viruses, cultural and climatic conditions and other pesticides may cause plant
responses similar to herbicide injury. Minor cases of damage may be undetected
or ignored. Injury by chlorophenoxy herbicides is characterized by visual symp-
toms in crops, commonly by petiole epinasty and deformities of expanding and
new leaves, and, in some cases, stem, root and fruit abnormalities. Losses in
yield or quality may occur on plants without visible symptoms or on plants which
apparently recovered from exposure. Susceptible- crops include cabbage, celery,
eggplant, lettuce, okra, pepper, radish and southern pea.
Minute amounts of 2,4-D may be detected by chemical analyses of plant tissue.
CAUSES of 2,4-D DAMAGE Physical drift of spray as an aerosol or mist from
the spraying site to sensitive plants is the immediate cause of injury. Fine
particles of spray can drift for miles, particularly when applied by aircraft.
Vapor injury is rare when amine salts and low-volatile formulations are used.
The basic cause of 2,4-D damage is usually traced to personnel and operating
procedures. Safe use of 2,4-D and 2,4,5-T requires trained and supervised per-
sonnel, knowledge of sensitive crop locations, proper chemical formulation and
.dosage, proper application equipment and operation, and, attention to wind con-
AVOID 2,4-D DAMAGE BY EFFECTIVE ORGANIZATION Keep an accurate base map of
fields and nearby (1 to.4 miles) vegetablelcrops. Safe wind direction and velo-
city for 2,4-D application in each field should be noted. Maintain an accurate
record of each 2,4-D application with date, wind direction and velocity, chemical
formulation and dosage, water volume, spraying pressure, spray unit number and
operating personnel for each field. Train supervisory personnel in proper pro-
A revision of Mimeo Report EES 64-12 which detailed and repeated prior cautions
on safe use of 2,4-D.
Associate Horticulturist, University of Florida, Everglades Experiment Station,
Belle Glade, Florida.
AVOID 2,4-D DAMAGE BY EFFECTIVE PROCEDURES Use the proper 2,4-D formula-
tion; amine salts or low-volatile esters. Never use other esters. Use the
proper dosage never more than 2 Ib./A. acid equivalent for 2,4-D; use the
lowest rate that will control the problem weeds. Use proper equipment adjusted
to avoid spray drift. Large spray droplets minimize drift.. Use a brush-boom
sprayer with the boom as low as possible consistent with good coverage of the
weeds. Use large diameter flat-fan herbicide tips, Do not use cone tips.
Operate at low spraying pressures not over 25 psi at the nozzle tip. Use low
volumes of water 10 to 20 gallons of spray per acre. Use the fastest practi-
cal sprayer speed which permits use of large-orifice tips, low pressure and low
volume. Do not spray more than 10% of any farm unit per day except when fields
are well isolated.
Observe wind direction and velocity precautions/ Chlorophenoxy herbicides
should not be applied within one-half mile of susceptible crops except under the
most carefully controlled and supervised conditions. These chemicals should not
be applied when the wind velocity at boom.height exceeds 8 mph in isolated areas
or when wind exceeds 4 mph when sensitive crops are grown less than 2 miles down-
wind. Application should be avoided during periods of unsettled weather and when
variable winds, strong temperature inversions and turbulent weather exist or are
AERIAL APPLICATION: Ground equipment is preferable for most of the local
sugarcane, pasture and sod area. Aerial spraying of chlorophenoxy herbicide
materials greatly increases the risk of spray drift and damage. Aerial appli-
cation requires constant caution and should be utilized only in well-isolated
areas under rigidly controlled conditions. Spraying should be suspended when
wind velocity exceeds 5 mph at spray altitude. Aircraft wind-tip vorticies
"drag" spray aerosols to turn altitudes. Strong temperature inversions and
turbulent air movement prevent drift control. A plume of smoke from a burning
rubber tire or from a smoke generator facilitates estimation of wind direction
and velocity at various heights above ground level. Flight patterns should con-
form to crop conditions and ferry flights should avoid vegetable crop areas.
CONSEQUENCES OF MISUSE: Chlorophenoxy herbicides are valuable, economical
tools for control of broadleaf weeds in sugarcane, pastures, sod, rights-of-way
and waterways. Careless use causes sensitive plant damage, unfavorable publicity,
damage claims, litigation and needless expense. Repeated, indiscriminate use and
frequent crop damage could lead to legislation restricting the use of these herbi-
cides. Unfortunately, legislation is not a cure-all nor is it a guarantee prevent-
Pocket or portable wind guages are useful. One type is available as a
"Pocket Wind Meter" from the F. W. Dwyer Mfg. Co., Michigan City, Indiana.