Everglades Station Mimeo Report EES64-12 Novmber, 1963
USE 2,4-D SAFELY /
J. R. Orsenigo / /
Chlorophenoxy herbicide (2,4-D) injury to susceptible vegetable crops in the
Everglades farming area increased greatly during the past year. Much of this "cop
damage was related to sugarcane weed control operations. Additional'cases of crop
exposure may have been undetected or ignored.
Poorly controlled use of 2,4-D (and 2,4,5-T) is a direct, immediate hazard to
vegetable production in the area.
AGRICULTURAL CROP DAMAGE: The most common damage is visible: vegetable
appearance, quality and yield are affected. Contamination with illegal residues
is a new and more subtle form of damage to food crops. A 2,4-D tolerance has been
established for only 1 vegetable.
NON-AGRICULTURAL CROP DAMAGE: Many plants of urban areas; ornamentals, home
gardens and nurseries, are susceptible also to damage by chlorophenoxy herbicides.
DETECTION AND IDENTIFICATION OF DAMAGE: Positive determination of 2,4-D damage
is not always simple since diseases, insects, viruses and cultural and climatic
conditions may cause plant responses similar to herbicide injury. It is likely that
minor cases of chlorophenoxy herbicide damage are not perceived. Primary detection
of 2,4-D injury is based on visual symptoms in crops. Injury is characterized most
commonly by petiole epinasty and deformities of expanding and new leaves, and, in
some cases, stem, root and fruit abnormalities. Plants without visible symptoms,
or those apparently recovered, may have sustained damage not manifested until harves4
when losses in yield and quality are noted. Fruit abnormalities are found often in
tomato and snapbean exposed to 2,4-D drift. Included among susceptible crops are:
cabbage, celery, eggplant, lettuce, okra, pepper, radish and southern pea.
New analytical methods permit chemical detection of minute quantities of 2,4-D
in or on plant tissue.
CAUSES OF 2,4-D DAMAGE: The immediate cause of damage usually is the physical
drift of spray particles, as an aerosol or mist, from the treatment site to sensitive
plants. Varorization and vapor drift after application are less common causes.
The underlying cause of damage may be traced to personnel and operating pro-
cedures. Safe use of 2,4-D requires properly trained and supervised personnel,
knowledge of susceptible crop locations, proper chemical formulation and dosage,
proper application equipment and operation, and, attention to wind conditions.
/ This mimeo details and repeats previous cautions on the use of 2,4-D.
Associate Horticulturist, University of Florida Everglades Experiment Station,
Belle Glade, Florida.
Fine particles of spray mist can drift or be wind-borne for considerable dis-
tances. Damage symptoms in tomato and southern pea have been noted several miles
from 'cane fields receiving aerial sprays of 2,4-D.
AVOID CAUSING 2,4-D DAMAGE BY:
1. Effective organization
a. Establish and maintain up-to-date a base map of fields and adjacent
areas, particularly indicating location of nearby (1 2 miles) vegetable crop
fields. Note safe wind direction and velocity for 2,4-D application in each
b. Maintain an accurate log or record of each 2,4-D application in-
cluding date, wind direction and velocity, formulation and dosage, water
volume, spraying pressure, spray unit number and personnel for each treated
c. Train supervisory personnel in proper spraying procedures and stress
their responsibility for safe application and continued supervision of crews.
2. Effective procedures.
a. Use the proper 2,4-D (and/or 2,4,5-T) formulation. Amine salts are
preferred and practically preclude vapor-type injury. Low-volatile esters
usually are satisfactory. Never use other esters.
b. Use proper chemical dosage. Never apply more than the cleared rate
(2 lb/A acid equivalent for 2,4-D) and use a lower rate if it will control the
c. Use proper equipment. Crop damage can be minimized or avoided by
preventing spray drift during application. The mcst effective way to prevent
drift is to increase spray droplet size; adhere to the following:
Adjust boom height as low as possible consistent with good spray
coverage of weeds. Use a brush boom sprayer.
Use correct nozzles large-diameter orifice flat-fan herbicide
or flat-fan flooding tips. Cone tips should not be used; they develop
a wide range of droplet sizes and cause excessive misting.
Operate at low spraying pressures not over 25 psi at the nozzle
Use low volume sprays in water at 10 20 gallons of spray per
Use fastest practical sprayer speed which permits use of large-
orifice tips, low pressure and low volume.
d. Restrict acreage treated daily. Do not cover more than 10% of any
farm unit per day except when fields are well isolated; this practice will
reduce atmospheric contamination near the treated fields and also downwind.
e. 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 downwind. Application should be avoided during periods
of unsettled weather and when variable winds, strong temperature inversions
and turbulent weather exist or are anticipated.
AERIAL APPLICATION: Ground equipment is preferable for most of the local
sugarcane, pasture and sod area. Aerial spraying of chlorophenoxy herbicide
matcrialo greatly iicreaco the risk of spray drift and damage. Aerial application
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. Flight patterns should conform 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. More than 10 states currently have laws pertaining to chlorophenoxy herbi-
cide use. Unfortunately, legislation is not a cure-all nor is it a guarantee
EESMimeo Rpt. 64-12
/ 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.