J. C. Joyce and K. A. Langeland
The history of aquatic plant management parallels the introduction of
alligator weed (Alternanthera philoxeroides), water hyacinth (Eichhornia
crassipes), hydrilla
(Hydrilla verticillata) and Eurasian water milfoil (Myriophyllum
spicatum) into the United
States.
The introduction of water hyacinth in 1884 quickly and seriously affected
the navigability of southeastern lakes and rivers. The most authentic information
on the introduction of the water hyacinth into Florida indicates that a visitor returning from the
Cotton
States Exposition in New Orleans in 1884 brought with him several of the plants. Perhaps
because
of the showy lavender flower, the plants were placed in a lawn fountain on the banks of the St.
Johns
River near Palatka, Florida. As the plants rapidly multiplied and filled the pond, excess plants
were
discarded into the St. Johns River. By 1896 the plants had spread throughout most of the basin,
and
by 1898 the plant population had increased to the point that steamboats and other vessels were
unable
to reach docks or pass through navigation openings in bridges or narrow points in the river.
Another
major exotic plant pest, alligator weed, was introduced into the U. S. from South America in the
late
1800s. Alligator weed is thought to have been introduced by way of ballast dumped from sailing
ships.
Public concern over the economic impact of water hyacinth prompted the U.S. Army Corps
of Engineers (COE) to investigate the magnitude of the problem and report to Congress on a
proposed plan of action. This report resulted in the initial authorization for the control of
waterhyacinth in federal navigation projects under Chapter 425, Section 1, River and Harbor Act
of
1899. This act authorized the construction and operation of vessels and log booms for the
removal
and containment of water hyacinth in navigable waters of Florida and Louisiana. These methods
did
not prove adequate to manage the problem.
In 1902 Congress authorized the extermination and removal of water
hyacinths by any
mechanical, chemical, or other means. Various materials were tested including muriatic acid,
sulfuric
acid, carbolic acid, kerosene, steam, sodium arsenite, mercury bichloride, whale oil soap,
formaldehyde, copper sulfate, potassium bichromate, and many others. Although there were no
laws
to regulate the use of pesticides, it was quickly learned that most of the chemicals which were
effective against water hyacinth were also toxic to cattle and humans. In 1905 Congress
prohibited
the use of any chemical which was injurious to cattle or man. However, rather than completely
abandon research on chemical control it was thought that repellents could be found which, when
added to the spray, would prevent cattle from eating the sprayed plants. Some of the repellent
substances tried were cow manure, tobacco, camphor oil, petroleum, cinnamon oil, citronella,
idoform, rotten eggs, decayed meat, macerated blood mixed with water, and others. These first
adjuvants (additives) were either not effective or
uneconomical.
Between 1900 and 1950 only mechanical methods of water hyacinth control were available
(Figure 1). These methods were inefficient and temporary. During this period, the rivers and
lakes
were severely affected by water hyacinth and alligator weed with frequent blockages of channels
and
complete coverage of coves and backwater areas.
During 1944 to 1946, evaluations of a newly discovered herbicide, 2,4-D, as a control agent
for water hyacinth were initiated by the U. S. Department of Agriculture, Jacksonville District
Corps
of Engineers, and the Everglades Experiment Station of the University of Florida.
The
herbicide 2,4-D proved extremely effective and economical, and above all was not toxic to fish,
cattle, or humans. Various agencies began both ground and aerial applications of 2,4-D in
1947 and this marked the beginning of the modern age of aquatic plant
management. For the first time in decades, many miles of infested streams were
open to navigation and as time passed the control operations shifted back into feeder areas and
aquatic weeds became less of a threat to navigation and other uses of open water.
At approximately the same time 2,4-D was arriving on the scene, a resolution was passed by
the U. S. House of Representatives calling for a "review of reports on water hyacinth
obstructions
in
the United States." The results of that study, which was conducted by the U. S. Fish and Wildlife
Service, the U. S. Department of Agriculture (USDA), the Public Health Service and the COE,
were
used as the basis for passage of Section 104 of Public Law 85-500 on July 3, 1958. This
landmark
legislation authorized a comprehensive 5-year project for the control and progressive eradication
of
water hyacinth, alligator weed, and other noxious aquatic plants from navigable waters, tributary
streams, and associated waters. Section 104 0f Public Law 85-500 was important
because it recognized that there were more reasons for aquatic plant control than just
navigation and authorized the expenditure of federal funds for aquatic plant control in the
interests of navigation, flood control, drainage, agriculture, fish and wildlife conservation,
public health and related purposes. The act provided for cost-sharing with local
governments providing 30% and the COE providing 70% of the total costs. The local
governments
were also required to "hold and save harmless" the federal government from claims that might
occur
from operation. A research program for the development of the most effective and economic
control
measures was also implemented.
One of the first major research efforts under the federally authorized research program was
the search for biological control agents for the major aquatic weeds of the day. In 1960, the COE
and the Agricultural Research Service of the USDA initiated efforts to search for biological
control
agents for alligator weed in its native range of South America. Many insects were discovered
and
studied to determine their ability to control alligator weed and determine if they were host
specific
(would perish in the absence of the host plant). These efforts resulted in the release of three
insects,
the alligator weed flea beetle (Agasicles hygrophila), alligator weed stem borer
(Vogtia malloi), and
alligator weed thrips (Amynothrips andersoni) between 1964 and 1971. This
biocontrol program was
tremendously effective and resulted in significant suppression of alligator weed in most
southeastern
waters.
Following the success with the alligator weed biocontrol agents, the USDA, COE, and Florida
DNR expanded the search for biocontrol insects for water hyacinth. This resulted in the
discovery
and
subsequent release of two water hyacinth weevils, (Neochetina eichhorniae, released
in 1972 near Ft.
Lauderdale and N. bruchi, released in 1974 in Broward County) and a moth,
(Sameodes albiguttalis),
released at three Florida locations in 1977. The biological control program is a continuing effort
among USDA, University of Florida and the COE.
A major change in the aquatic plant control situation occurred when
another noxious aquatic plant, hydrilla was introduced in the late 1950s. The
plant may have been unknowlingly introduced into canals near Miami and Crystal River by the
aquarium plant industry. Hydrilla quickly covered canals in these regions and caused severe
blockages of recreational navigation and flood control canals. The plant was initially thought to
be
Elodea sp. and was called Florida elodea. Proper identification was not made until 1966. By the
early 1970's it was established in major water bodies of all drainage basins in the state; and in
1988
the Florida DNR estimated over 20,000 ha (50,000 ac) in the state (in addition to 8,000 ha
(20,000
ac) that were controlled). Hydrilla is now found in all the Gulf Coast States, the Atlantic Coast
States
as far north as Maryland and Deleware, Tennessee and the Western States of California and
Arizona.
Hydrilla presented a new challenge to aquatic plant managers and researchers and, as with
waterhyacinth, initial efforts to control it were with mechanical means and various chemicals.
One
of the more famous tests that demonstrated the state's desperation to find a solution to the
problem
occurred in 1965 when 50,000 lb of sulfuric acid was pumped into a canal in the Crystal River
area
in an unsuccessful attempt to control hydrilla. Hydrilla continues to cause severe detrimental
impacts
to water resources and investigations continue to develop the most efficient herbicides, biological
control agents, mechanical devices and integrated methods for hydrilla management.
Just as hydrilla causes seriuos water use problems in the southeastern and mid-Atlantic states,
Eurasian water milfoil causes similar problems in more temperate regions, as well as in
southeastern
states. Eurasian water milfoil was first identified in the United states in 1942, from a
Washington
D.C.
pond. Through the 1940's, it was collected as far West as California. A recent study verified the
existance of 392 Eurasian water milfoil populations in 33 states, and there are no doubt more
than
these verified populations. Eurasian water milfoil continues to spread from lake to lake and will
require greater management efforts in the future.
This brief history of aquatic plant management demonstrates the enormous efforts that
have gone into developing present day aquatic plant management programs. These programs use
specialized machinery, carefully studied biological control agents, safe and effective herbicides
and
other methods alone or together, depending upon conditions of individual projects. These
methods
have been developed over a period of over 100 years of science and experience. It is the
responsibility of aquatic plant management professionals to learn from the experiences of those
before us and to build on the experiences to continually improve the field of aquatic plant
management.
Chronolgy of Aquatic Plant Management Events (1884-1977)
1884
_______________________________________________________________
Figure 1. Until about 1950 only mechanical methods of aquatic weed
control were available. Here, the U.S. Army Corps of Engineers uses a barge mounted grapple to
remove water hyacinths from a canal near Lake Okeechobee, Florida. (Photo courtesy of U.S.
Army Corps of Engineers, Jacksonville District.)
Water hyacinth introduced
1885 First record of alligator weed
1899 River and Harbor Act of 1899 authorized construction and
operation of vessels and log booms for the removal and containment of water hyacinths in the
waters of Florida and Louisiana
1902 Congress authorized the extermination and removal of water
hyacinths by any
mechanical, chemical or other means
1905 Congress prohibited the use of any chemical that was injurious
to
cattle or man
1900-50 Mechanical methods of controlling water hyacinths proved
unsuccessful
1942 Eurasian water milfoil identified in Belch Spring Pond, District
of
Columbia
1947 2,4-D successfully controlled water hyacinth
1958 Section 104 of Public Law 85-500 authorized 5-year federal
project funds for the
control and progressive eradication of water hyacinths, alligator weed, and other
noxious aquatic plants from navigable waters, tributary streams and associated waters
in the interests of navigation, flood control, drainage, agriculture, fish and wildlife
conservation, public health and related purposes
1959 Hydrilla discovered in Florida
1965 Public Law 89-298 authorized nationwide continuing project
with funding not to
exceed $5.0 million annually and authorized a continuing research program for the
development of the most effective and economic control measures
1964-71 Alligator weed biological control agents released
1972-77 Water hyacinth weevils and water hyacinth moth
released
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