CONTROLLING WATER HYACINTHS WITH
2, 4-D IN SOUTH FLORIDA
J. C. Stephens, V. L. Guzman, and C. C. Seale
This report is based on research conducted co-
operatively by Florida Everglades Experiment
Station; Agricultural Research Service, U.S.D.A,;
and Central and Southern Florida Flood Control
Everglades Station Mimeo Report 55-12
Belle Glade, Florida
May 13, 1955
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Controlling Water Hyacinths With 2,4-D in South Florida
J. C. Stephens, V. L. Guzman, and C. C. Sealel
The Water Hyacinth (Eichhornia crassipes), a perennial aquatic weed,
is reported to have been introduced into the United States at the Cotton
Centennial Exposition in New Orleans in 1884 from South America. Native
to Japan, it thrived well in the climate of southeastern United States,
and by 1890 had invaded the fresh waters of Florida where it soon became
a widespread pest. This floating, mat-forming plant has been called the
"million dollar" weed because of its adverse effects on water control,
wildlife, and navigation. Water control is extremely difficult in a
system of infested waterways and canals. A cover of hyacinths will cut
the flow in large drainage canals to one-half of normal flow, and even
more in smaller laterals and farm ditches. Hyacinths carried by flood
waters frequently jam into dense masses at bridge piers and pump intakes
so that flow is almost completely stopped. They have been known to jam
up and push over wooden highway bridges in south Florida. Under floating
hyacinth mats the light is cut off so that submersed aquatics, some
valuable for duck food, do not grow; also, the oxygen supply in the water
is reduced to the point where only gar and mudfish survive. Navigation
is often completely blocked by a dense growth of water hyacinths.
The mature hyacinth plant consists of roots, rhizomes, stolons,
leaves, blossoms, and fruit clusters. The broad, green leaves extending
out and up from a central axis have an enlarged basal spread or float
filled with air sacs which allows the plant to float. Erect spiked
clusters of beautiful lavender blossoms are characteristic of this plant.
The hyacinth reproduces at an astounding rate. W. T, Penfound and
T. T. Earle2 have made an exhaustive study of water hyacinths in Louisiana
and report that under good growing conditions a floating mat of these
plants will grow outward about its periphery at the rate of 2 feet per
month, the plants doubling their numbers every 2 weeks by means of off-
shoots. At this rate only ten plants would produce about 650,000 plants
Drainage Engineer, Assistant Horticulturist, and Associate
The Biology of the Water Hyacinth, Ecological Monographs,
Vol. 18, No. 4, October 1948.
in approximately 8 months. It was noted that the individual plants vary
in size from a few inches under poor growing conditions, to several feet
under optimum conditions in well aerated canals. Propagation is accom-
plished primarily from vegetative reproduction rather than from seed. It
is doubtful if the seeds will germinate under water in south Florida. The
hyacinth does not tolerate brackish water. It is killed by prolonged
freezing, and will not survive where water temperatures remain much above
900 F. for long periods. Cattle often eat the plants; however, the water
content averages about 95 percent and they afford little sustenance.
Water hyacinths are susceptible to the effects of 2,4-D (2,4-Dichloro-
phenoxyacetic Acid) and can generally be controlled by an application of
1 pound of 2,4-D acid equivalent per acre.
When treated with 2,4-D the plants exhibit the following symptoms:
a few hours after spraying there is a marked bending of the leaf stems;
in about a week plants wilt and become brown in color; in three to four
weeks they die and form a floating mass which decomposes and sinks to
the bottom of the ditch about the sixth to eighth week after treatment.
Water current, wave action, and wind movement appear to be factors in
causing the dead material to sink. Studies in Louisiana indicate that the
plants sink quicker under heavier rates of 2,4-D application. This has
not been confirmed under south Florida conditions.
Water hyacinths are killed more rapidly in warm weather than in cool.
A poor kill may be obtained if the weather is cool or if rain falls within
6 hours after treatment with 2,4-D.
The quantity of 2,4-D acid used for the control of water hyacinths,
as well as for general weed control purposes, is not harmful to fish or
to warm-blooded animals.
TYPES OF 2,4-D
The most common types of 2,4-D which are available commercially are:
(1) Sodium salt of 2,4-D
(2) Amine salts of 2,4-D such as dimethylamine, alkanolamine, etc.
(3) Esters of 2,4-D
(a) high volatile types such as butyl, ethyl, isopropyl and
(b) low volatile types such as the propylene glycol butyl
ether, and other low volatile esters of 2,4-D
The sodium salt is available as a powder and the amine salts and
esters as liquids. Most of the commercial types of 2,4-D can be mixed
with water to obtain a spray mixture.
For general weed control, including water hyacinths, the amine salts
are recommended. In south Florida the amine liquid containing about 4
pounds of 2,4-D acid equivalent per gallon is generally used in preparing
the spray mix.
An application of 1 pound of 2,4-D acid equivalent per acre is generally
sufficient for controlling water hyacinths. This quantity of 2,4-D can be
mixed and applied in quantities of water varying from 2 to 150 gallons per
acre depending upon the method of application. The volume, or "bulk" of
the actual spraying solution, is only important in its relation to thorough,
uniform coverage. Using ordinary farm type spraying equipment from 50 to
100 gallons of solution will usually be needed to cover 1 acre. The labels
on commercial lots of 2,4-D amines usually show the number of pounds of
2,4-D acid equivalent contained in 1 gallon of the liquid. For example,
where the strength is 4 pounds of acid equivalent per gallon, which is a
common commercial formulation, 1 quart of the liquid should be applied
with suitable spray equipment to cover 1 acre regardless of the quantity
of water required.
Satisfactory application can be made with a variety of spraying
equipment ranging from knapsack type to large capacity power units, The
type selected will vary with the degree of infestation, the size of the
area to be treated, and the ruggedness of the banks and growth adjacent
to the canal or pond. Relatively inexpensive sprayers suitable for
applying sprays under low pressure up to 100 psi. are available
commercially and consist essentially of a rotary pump, pressure regulator,
suction hose, and boom and nozzles, or discharge hose and adjustable-spray
hand gun. If higher pressure 300 to 600 psi. is needed for reaching
remote weeds, then a somewhat more expensive plunger-type pump and high
pressure fittings are required. Both type units are usually powered by
light weight, air-cooled, gasoline engines.
It is best to work at low pressures and with a coarse spray, where
feasible, to reduce danger of spray drift. The higher the pressure used
the smaller the spray droplet size, and an extremely fine mist can be
easily carried by wind and harm sensitive crops in the vicinity. For
example, an 0.0008-inch-diameter spray particle, when released from a
height of 10 feet, reportedly, can drift a distance of about mile in a
3 mph. wind; whereas, droplets half this size can travel approximately
Sprays can be distributed most uniformly using a boom with flat
spray nozzles, or a boomless cluster of nozzles such as the "Boomjet" or
"Broadjet" which operate at pressures of 60 psi. or less and produce a
flat spray which gives uniform and complete coverage. These methods are
preferable where conditions allow the use of such equipment. However,
most agencies engaged in hyacinth control in south Florida use the
orchard type hand gun with an adjustable spray pattern because it is more
adaptable to the variety of conditions encountered.
The usual method' of application is spraying from a boat. However,
in many cases it may be best to mount the spraying equipment on a truck
and spray from the bank.
In calibrating the spray equipment and in calculating quantities it
will be helpful to remember that there are 43,560 sq. ft. in 1 acre and
also that a strip 8 feet wide, one mile long, is approximately 1 acre.
For low-volume, low-pressure type sprayers, the nozzle delivery rates
and speed of spray-rig travel are furnished by the manufacturer and may
be followed. If these are not available, the machine may be calibrated by
making a test run of a measured distance of, say, mile, and determining
the quantity of spray liquid applied. For example, let us suppose that
the following conditions prevailed: length of the test run was 1,320 feet
and width of spray swath was 16 feet, making a sprayed area of 21,120
square feet or about acre; quantity of spray liquid used in the test
run was 15 gallons. From these figures it can readily be determined that
about 30 gallons of spray was applied per acre. When the rate of spray
delivered per acre is ascertained, mix the required amount of 2,4-D amine
concentrate with this quantity of water so as to apply at the rate of
1 pound acid equivalent per acre.
High volume, high pressure gun-type spray nozzles are supplied with
interchangeable discs with different size holes ranging from 3/64 to
3/16 inches in diameter. Accordingly, they deliver from 1 to 14 gallons
per minute at 400 psi. pressure when the gun is set for wide open,
distant stream delivery. The discharge is from 10 to 20 percent less in
medium fog position. The capacities for the different size discs are
supplied by the manufacturer. The size orifice and pressure selected
should deliver the largest possible droplet size consistent with the re-
quired coverage and effective killing range of the spray stream. When the
amount of spray solution required to cover an acre has been determined by
trial, mix the killing solution so as to put on the spray at the rate of
1 pound acid equivalent per acre. If in doubt, it is usually satisfactory
to mix at the rate of 1 pound 2,4-D acid equivalent to 100 gallons of
water and apply the spray so as to cover the plants adequately.
The cost of controlling hyacinths with 2,4-D is cheap compared to
most of the manual or mechanical methods. Cost of 2,4-D amine concen-
trate, containing 4 pounds acid equivalent per gallon, varies from 3 to
4 dollars a gallon depending upon the quantity purchased. Thus, at the
recommended application rate the cost of the 2,4-D itself will run from
about 75 cents to a dollar an acre.
The cost of application may vary greatly depending upon the experi-
ence of the applicators, the type and capacity of the spray equipment,
and the density and accessibility of the hyacinth cover. Normally, with
power equipment, a two-man crew can be expected to treat from 10 to 40
acres per day.
A 90 to 95 percent kill can ordinarily be expected with the initial
application. If it is desired to eradicate the plants it will be necess-
ary to prevent reinfestation from other sources and to destroy the remain-
ing plants by removing them by hand or re-treating the remaining plants
with 2,4-D before they can repropagate.
(1) To avoid danger from drift, do not spray water hyacinths with
2,4-D when susceptible crops are growing at a distance of less than .
mile from the area to be treated or when the wind movement is greater
than 10 miles per hour, including the speed of the gusts. Due to the
volatility of esters, their use for spraying canals is not recommended.
The safest time for spraying will be after the harvest of sensitive crops.
(2) Water from canals treated with 2,4-D should not be used for
spraying or irrigating sensitive crops until a test indicates that this
water is np longer contaminated with 2,4-D. Such a test can be run by
spraying the canal water onto young tomato plants and by observing the
results obtained. If, under normal temperature, bending of the stem of
the plant does not occur within 24 hours the water is safe.
(3) For best results, 2,4-D in a water solution should not be
applied when rain is expected within 6 hours after spraying.
(4) Water hyacinths should be treated with 2,4-D whenever possible
when temperatures are high.
(5) Sprayers which have been used for 2,4-D should never be used
for spraying susceptible crops.
(6) When feasible, operate spray machines with a coarse spray at
low pressure in order to reduce drift.
(7) Maintain the spray boom at as low a level as possible to obtain
a good spray pattern and to avoid spray drift.
(8) 2,4-D should not be stored in the same building with agricul-
tural chemicals, products, or equipment.
For information on use of 2,4-D on crop land, consult Bulletin 532,
University of Florida Agricultural Experiment Stations; "2,4-D FOR POST-
EMERGENCE WEED CONTROL IN THE EVERGLADES," which may be obtained on
request from the Agricultural Experiment Station, Gainesville, Florida.