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Bennett, F. D. 1966. Investigations on the insects attacking the
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Bennett, F. D. 1968. Insects and mites as potential controlling agents

of water hyacinth (Eichhornia crassipes (Mart.) Solms). Proc.
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DeLoach, C. J. 1975. Search for and importation of insect
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Bennett, F. D. 1975. Insects and plant pathogens for the control of
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Perkins, B. D. 1973. Host specificity and biology studies of Neochetina
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Perkins, stet. D. 1974. Biocontrol of water hyacinth. p. E3-E17. In
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Waterways Exp. Sta., Vicksburg, Miss. (NTIS AD-775 408/8)

Bennett, F. D., and H. Zwolfer. 1968. Exploration for natural enemies
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Hyacinth Control J. 7:44-53.

DeLoach, C. J. and H. A. Cordo. 1976. Life cycle and biology of _
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53


an opening cut in the plant prior to pupation (88).

Arzama--

A native moth, Arzama densa, is also under investigation as a water
hyacinth control (114). The young larvae feed upon tender parts of the
hyacinth and bore into the plant as they grow older (88, 134, 135). Damage
caused by this insect may be extensive; over 70 percent of the water hya-
cinths covering a small pond were affected within four months after the pond
was innoculated with 30 larvae/m? (88) While A. densa is a potential bio-
logical control agent, it has not yet been effective in the natural envi-
ronment, perhaps because of parasites (136, 137). Habeck (138) warned that
the moth should not be introduced into countries where dasheen (Calococisia
esculentais) is grown as a root crop because of dangers of infestation.

Parapoynx--

Parapoynx stratiota, a Yugoslavian moth, has demonstrated potential in
the control of Eurasian watermilfoil (128, 139). Only the adult stage is
spent above the water surface (140) and one caterpillar can eliminate 8-12
50 cm plants (141). P. allionealis, a closely related species, is also un-
der study (140).

Other Lepidopterans--

A number of other lepidopterans have been tried or proposed as biologi-
cal controls. Epipagis albiguttalis attacks water hyacinth in South America
and may be introduced into the United States after adequate testing (131,
133). Samea multipicalis has been introduced into Kariba Lake, Africa, from
Trinidad for control of Salvinia spp. but the results are unknown (79).

This species also attacks water lettuce (142). The moth Erastroides curvi-
fuscia has been studied in India, where in prelimimary tests, 17-86 larvae/
m* cleared 1,230-1,340 g of water lettuce in 30-40 days (143). Nymphula
caterpillars have been suggested for coontail Ceratophy Tum demersum
control in New Zealand (144) and the leaf miner Hydrellia appears to be
specific in attacking Hydrilla in Pakistan (124).

Cornops--

Cornops aquaticum, a grasshopper native to South America has been
studied as a possible control for water hyacinth in the United States (88,
133, 137). C. longicorne has also been considered (136, 145); however, some
investigators believe it might be detrimental to other plants (75, 89).

Paulina--

The grasshopper Paulina accuminata was introduced into Kariba Lake,
Africa, from Trinidad to control Salvinia; however, results were uncertain.
This insect was also suggested as a possible control of water lettuce in the

United States (80).

Thrips--

A species of thrips, (Amynothrips andersoni), an important suppressant
of alligator weed in South America 746). was introduced into the United
States in 1967 (104, 105). This insect creates lesions which cause the
leaves to distort and become stunted (110). Population densities of thrips
sufficient to control alligator weed have not yet developed, possibly due

19


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields
The nine series are

Environmental Health Effects Research

Environmental Protection Technology

Ecological Research

Environmental Monitoring

Socioeconomic Environmental Studies

Scientific and Technical Assessment Reports (STAR)
Interagency Energy-Environment Research and Development
“Special” Reports

9. Miscellaneous Reports

This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments

MNAMSEwWNH

This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161


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manatee research: report of a workshop held 7-13 February 1974 in
Georgetown, Guyana, South America. 39. p. (NTIS PB-240 244/4GA)

Ingersoll, J. M. 1974. The water hyacinth. p. A3-A33. In Gangstad,
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Bertram, G. C. and C. K. Bertram. 1962. Manatees of Guiana. Nature
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5(9) :60-65.

Allsopp, W. H. 1960. The manatee: ecology and use for weed control.
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Bertram, G. C. L. and C. K. R. Bertram. 1968. Bionomics of dugongs and
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MacLaren, J. P. 1967. Manatees as a naturalistic biological

mosquito control method. Mosquito News 27(3):387-393.
(Biol. Abstr. 49:86328)

73


TABLE 1 (continued)

Problem or Project Solution or Proposed Treatment Location Results or Remarks References
Overabundant Northern pike Colorado Successful at 62 15-cm fish/ha 371
panfish ‘in reservoirs
B. PATHOGENS
Zooplanktivorous Fish diseases wee Proposed as means to decrease 442
fish phytoplankton by increasing
zooplankton
Tilapia Hybridization California Under study as means to develop 490
control fish which do not
reproduce in wild
Fish Sterilization and sex-reversal aad Suggested to control fish 369, 483, 485
populations
IV INSECTS
A. PREDATION
Mosquitoes White amur ULS.S.R, Proposed as control since amur 351
consumes plants upon which
insects depend
Chironomid Carp and goldfish California Effectively reduces nuisance 354
midges outbreaks in limited situations

Chaoborid midges

Mississippi silversides
(Menidia audens)

California

Has had little impact

63, 356 R. Brown
Pers. Comm.



256.

257.

258.

259,

260.

261.

264.
265.

266.

267.
268.

Landner, L. 1974. Production and use of herbivorous fish. Swedish
Water and Air Pollution Research Laboratory. Nordforsk Publ.
1:121.  (Abstr.)

Bailey, W. M. and R. L. Boyd. 1973. A preliminary report on spawning
and rearing of grass carp (Ctenopharyngodon idella) in Arkansas.
p. C3-C16. In E. 0. Gangstad, J. J. Raynes and R. M. Burress, et
al. Herbivorous fish for aquatic plant control. Aquatic Plant
Control Program, Tech. Rep. 4, U. S. Army Eng. Waterways Exp. Sta.,
Vicksburg, Miss. (NTIS AD-765 437)

Hickling, C. F. 1972. The artificial inducement of spawning in the
grass carp, Ctenopharyngodon idella Val. App. D. p. 1-9. In
Gangstad, E. 0., D. E. Seaman, and M. L. Nelson. Potential growth
of aquatic plants in the Republic of the Philippines and projected
methods of control. Office of the Chief of Eng. (Army), Washing-
ton, D. C. (NTIS AD-901 645L)

Stanley, J. and K. Sneed. 1973. Scope of Corps of Engineers coopera-
tive research aquatic plant control program, white amur studies.
p. 83-B18. In E. 0. Gangstad, J. J. Raynes and R. M. Burress, et
al. Herbivorous fish for aquatic plant control. Aquatic Plant
Control Program, Tech. Rep. 4, U. S. Army Eng. Waterways Exp. Sta.,
Vicksburg, Miss. (NTIS AD-765 437)

Food and Agriculture Organization of the United Nations. 1975. Pro-
duction of monosex grass carp. FAO Aquacult. Bull. 7(1-2):6.

Stanley, J. G., J. M. Martin, and J. B. Jones. 1975. Gynogenesis as a
possible method for producing monosex grass carp (Ctenopharyngodon
idella). Prog. Fish Cult. 37(1):25-26.

. Bailey, R. M. 1972. Grass carp symposium. Grass Carp Symp. 102nd Ann.

Meeting, Amer. Fish. Soc. Hot Springs, Ark. 5 p.

3. Ellis, J. E. 1974. Observations on the jumping and escapement of white

amur. Prog. Fish Cult. 36(1):15.
Sport Fishing Institute. 1975. Grass carp binge. SFI Bull. 266:8.

Lowe-McConnell, R. H. 1973. Summary: Reservoirs in relation to man--
fisheries. Geophys. Monogr. 17:641-654.

Bond, C. E. 1972. Grass carp: view from the Northwest. Grass Carp
Symp. 102nd Ann. Meeting, Amer. Fish. Soc. Hot Springs, Ark. 4 p.

Oregon Wildlife. 1975. Not wanted--the white amur. 30(1):2, 12.
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point. Grass Carp Symp. 102nd Ann. Meeting. Amer. Fish. Soc.
Hot Springs, Ark. 4 p.

68


Spawning considerations--Since the amur does not often spawn outside of
its native area, spawning must be frequently induced artifically in other
locales. Successful spawning has been achieved in Arkansas under artificial
conditions using human chorionic gonadotropin (257). Hickling (258) reviewed
and summarized this procedure.

Ware et al. (46) recommended that future programs involving amur should
include only sterile or monosex fish. The production of monosex cultures of
amur would insure that the fish could not breed in nature and would alleviate
some of the problems of exotic species introduction. However, gynogenesis, a
method of producing monosex fish by fertilization with genetically inactivated
sperm (259, 260) was determined impractical for mass production (261).

Bailey (180) considered the danger of spawning in the United States to
be slight since the amur normally spawns in nature in a strong current after
a rapid water rise (180). Widespread introduction in this country however,
would eventually place it in suitable spawning locations (262). The fishes
jumping ablity could lead to its spread from farm ponds into waters where its
establishment is not desired (263). Amur are collected occasionally from the
Mississippi River, presumably escapees from Arkansas (264); similarly, escaped
fish also are found in the rivers of East and Central Europe (Holcik, Holcik
and Par, cited in 265).

The Columbia River drainage system might provide conditions suitable for
spawning with the subsequent danger of natural vegetation reduction in water-
fowl habitats (266, 267). Spawning conditions might also be satisfied in
some Missouri streams (268) and the fish could eventually become established
throughout the Mississippi River Basin (269). The amur was not recommended
for introduction into California because the possibility of its establishment
in some of the larger rivers would be detrimental to native game fish (270,
271). In Florida, the fish might also spawn in some rivers used by the
native striped bass (Morone saxatilis), and could possibly harm the sport
fish production potential of the littoral zone in lakes (46). Alabaster and
Scott (272) believed the amur had the potential to breed in Great Britain in
some of the faster flowing rivers receiving heated effluents, and perhaps in
some sluggish rivers in southwest England.

Although spawning is often believed restricted to native areas, natural
reproduction has occurred in other regions. The amur has spawned in the Tone
River in Japan since 1947 (273). Spawning has been reported from a fish pond
in the Ukraine (Prikhodko and Nosal, cited in 272). It has also reproduced
in a 360 ha reservoir in Taiwan where it had become established after finger-
lings escaped from a nearby pond (53). Natural reproduction has taken place
in a river and lake system in Mexico after the fish were released following
water hyacinth control experiments (274, 275).

Control of the amur--Toxicants could be used to control the amur as it
is about as sensitive to those materials as the common carp (276). Antimycin
applied at 6 mg/1 and rotenone applied at 2 mg/1 killed all the amur in
experimental ponds within 16 days (277). The amur is sensitive to 0.006 ppm

26


to withstand winter temperatures (348). Contributions of these animals to
the nutrient loading of the water should be considered in any proposed con-
trol program.

CONTROL OF INSECTS

. Nuisance insect emergences can be a part of eutrophic systems and
biological means are one approach to their control. Most efforts have
concerned mosquitoes (349, 350). Amur have been proposed for mosquito con-
trol in Russia since they will consume plants upon which the insects depend
(351). Tilapia have also been considered for mosquito control, as well as
for control of chironomid midge larvae (301, 352, 353).

Nuisance outbreaks of chironomid midges have been effectively reduced in
limited situations by carp and goldfish stocked at 168-562 kg/ha. As their
control efficiency is usually inversely proportional to the area of midge
production, they are less valuable for control in large lakes (354). The
leech, Helobdella stagnalis, plays a significant role in the population
dynamics of a chironomid midge in a Wisconsin lake (355) and may merit fur-
ther investigation.

Mississippi silversides were introduced into Clear Lake, California, to
help control the “gnat", Chaoborus astictopus (62, 63, 356). However, it
apparently has had little impact. R. Brown, pers. comm.).

CONTROL OF FISH

The control of undesirable fish in eutrophic lakes through stocking of
predator species is a way to establish more desirable and valuable fish
populations (17). Predatory fish have long been stocked to control other
species (357) and forage fish are often introduced to increase production of
large piscivorous species (358). Beard (359) presented a literature review
on the population dynamics, environmental and biological influences, life
histories and current management techniques on predator stocking to control
panfish. An annotated bibliography on bluegill stocking was compiled by
Graham (360).

Predator stocking to control panfish is rarely effective (359, 361,
Klingbeil and Snow, cited in 362). Stocking of walleyes (Stizostedion
vitreum) to control panfish populations in a number of Wisconsin lakes was
ineffective (363); in general, most walleye stocking attempts have failed,
perhaps related to a lack of suitable spawning requirements (364). Bluegills
(Lepomis macrochirus) in some Alabama ponds were not controlled by spotted
gar (Lepisosteous oculatus) (365) nor by largemouth bass (Micropterus salmoides)
in an Ohio lake (366). A variety of management procedures including heavy
stocking of forage fish, heavy stocking of predators and no stocking at all
failed to produce changes in fish populations in an Ohio lake (367).

Some instances of successful stocking have been reported. Young

muskellunge (Esox masquinongy) placed into two Wisconsin lakes to control
perch (Perca flavescens ond bass nearly eliminated the perch within a year;

33


129.

130.

131.

132.

133.

134,

135.

136.

137.

138.

139.

Spencer, N. R. 1974. Biological contro] of Eurasian watermilfoil. p.
75-84. In: Proc. Research Planning Conf. on Integrated Systems of
Aquatic Plant Control. Army Eng. Waterways Exp. Sta., Vicksburg,
Miss. (NTIS AD-787 302)

Brown, J. L. and N. R. Spencer. 1973. Vogtia malloi, a newly intro-
duced phycitine moth (Lepidoptera:Pyralidae) to control alligator-
weed. Environmental Entomol. 2(4):519-523.

Spencer, N. A. 1975. Biological control of weeds with insects, U. S.
Dep. Agr., Biological Control Laboratory, Gainesville, Florida.
Notice of Research Project, Smithsonian Science Information Ex-
change, Washington, D. C. SIE No. GTK-21.

Maddox, D. M. 1970. The bionomics of a stem borer, Vogtia malloi
(Lepidoptera: Phycitidae) on alligatorweed in Argentina. Entomol.
Soc. Amer. 63(5):1267-1273.

DeLoach, C. J. 1975. Evaluation of candidate arthopods for biological
control of water hyacinth: Studies in Argentina. p. 44-50. In
Brezonik, P. L. and J. L. Fox (eds.) Proc. symp. on water quality
management through biological control. Univ. of Florida and U. S.
Environmental Protection Agency, Gainesville, Jan. 29-31.

Vogel, E. and A. D. Oliver, Jr. 1969. Life history and some
factors affecting the population of Arzama densa in Louisiana.
Entomol. Soc. Amer. 62(4):749-752.

Vogel, E. and A. D. Oliver, Jr. 1969. Evaluation of Arzama densa as an
aid in the control of water hyacinth in Louisiana. J. Econ. Ento-
mol. 62(1):142-145.

Bennett, F. D. 1970. Insects attacking water hyacinth in the West
Aster British Honduras and the U. S. A. Hyacinth Control J.
8(2):10-13.

Gordon, R. D. and J. R. Coulson. 1974. Field observations of arthro-
pods on water hyacinth. p. B3-B37. In Gangstad, E. 0. J. J.
Raynes, C. R. Zeiger, J. M. Ingersoll, R. D. Gordon, et al. Bio-
logical control of water hyacinth with insect enemies. Aquatic
Plant Control Program, Tech. Rep. 6. Army Eng. Waterway Exp. Sta.,

Vicksburg, Miss. (NTIS AD-775 408/8)

Habeck, D. H. 1974. Arzama densa as a pest of dasheen. Fla. Entomol.
57(4) :409-410.

Sailer, R. I. 1970. Insect enemies of Eurasian water milfoil--a pro-
gress report. Proc. Weed Sci. Soc. Amer. 10:5-6. (Abstr.)

58


numbers (291) and stocking rates in ponds have ranged from 2,470 to 6,765
fish/ha (40, 61, 302).

Although T. melanopleura effectively controls some aquatic plants, its
use in Florida was considered potentially harmful because of its competitive-
ness and reproductive potential (46). Phillippy (149) reported that it can
live in 100 percent sea water, although adults refused food at concentrations
higher than 66 percent. He emphasized that since the fish can adapt to sea
water, it has the potential to migrate from one Florida watershed to another
through the Atlantic Ocean or Gulf of Mexico and perhaps establish itself to
the detriment of native fishes. It has also been reported as a menace to all
vegetation and small fish in various Rhodesian water bodies (303) and may
devour rice seedlings if stocked in irrigation canals (36).

T. zillii also consumes sprouting rice (296) and so should be used with
caution in irrigation canals (36). JT. randalli randalli, a prolific breeder
with destructive weed eating habits, was considered potentially harmful to
desirable vegetation in Lake Kariba, Rhodesia (304). Tilapia may also have
had a detrimental effect upon other members of the aquatic community in Lake
Mcllwaine, Rhodesia, in spite of its success in weed control (van der Lingen
and others, cited in 17). It was abandoned in weed control projects in the
Sudan (146) and by the U.S. Bureau of Sport Fisheries and Wildlife because of
disappointing results (60).

The ability of tilapia to reproduce rapidly in waters free of any
natural enemies was demonstrated in an 8 ha pond containing over 30 species
of plants and 19 species of frogs; plants and animals were virtually eli-
minated two years after the introduction of 20 T. mossambica and 20 T.
melanopleura (305). The dangers of introducing species with destructive
potential has been demonstrated by T. aurea. Courtenay et al. (306) and
Courtenay and Robins (282) have described how this species has spread
throughout central and western Florida, after its introduction as a test
organism, competing with the native fish. It now dominates the fauna in many
eutrophic Florida lakes (307). The tolerant characteristics of tilapia have
also allowed them to colonize relatively inhospitable habitats in Africa
subject to extremes of temperature, salinity and pH (308, 309).

Common and Israeli Carp--

The ability of the common carp to completely eliminate vegetation by
uprooting with a subsequent increase of light limiting turbidity was re-
cognized at an early date (310, 311, 312, 313). Although the carp is highly
adapted to feed upon benthic fauna (314) it is reported to selectively
consume or destroy sago pondweed, (Potamogeton pectinatus), coontail, elodea
and pickerel weed in that order (315).

Submersed vegetation in some Alabama ponds was controlled with 400
common carp/ha (39). A carp density of 448 kg/ha was excessively destructive
to submersed vegetation in some Lake Erie marsh enclosures (316). It is
used for weed control in Poland (317) and is planned for introduction into
Sudan to both control weeds and provide a badly needed source of animal

29


167.

168

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small Ohio pond. Prog. Fish Cult. 34:55-58.

Rickett, J. D. 1974, _Trophic relationships involving crayfish of the
genus Orconectes in experimental ponds. Prog. Fish Cult. 36(4):

Dean, J. L. 1969. Biology of the crayfish Orconectes causeyi and its
use for control of aquatic weeds in trout Takes. U. S Sin Sport-
fish. Wildlife Tech. Pap. 24:3-15.

Friberg, D. 1974. The crayfish (Orconectes causeyi) as a biological
control of aquatic vegetation, 1972-73, South Dakota. South Dakota
Dept. Game, Fish and Parks. Dingell-Johnson Project F-15-R-8. 7

p.

Army Engineer District, Walla Walla, Wash. 1972. The crayfish Paci-
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Magnuson, J. J., G. M. Capelli, J. G. Lorman, and R. A. Stein. 1975.
Consideration of crayfish for macrophyte control.
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Florida and U. S. Environmental Protection Agency, Gainesville,
dan. 29-31.

Yount, J. L. and R. A. Crossman, Jr. 1966. Causes and relief of
hyper-eutrophication of lakes. Florida State Board of Health, Vero
Beach. Entomological Research Center. 67 p. (NTIS PB-228 045/1)

Bailey, W. M. and R. L. Boyd. 1972. Some observations on the white
amur in Arkansas. Hyacinth Control J. 10:20-22.

Michewicz, J. E., D. L. Sutton, and R. D. Blackburn. 1972. The white
amur for aquatic weed control. Weed Sci. 20(1):106-110.

Johnson, M. and J. M. Laurence. 1973. Biological weed control with the
white amur. p. E3-E12. In E. 0. Gangstad, J. J. Raynes and R. M.
Burress, et al. Herbivorous fish for aquatic weed control. Aqua-
tic Plant Control Program, Tech. Rep. 4, U. S. Army Eng. Waterways
Exp. Sta., Vicksburg, Miss. (NTIS AD-765 437)

Sneed, K. E. 1971. The white amur: A controversial biological con-
trol. Amer. Fish Farmer and World Aquacult. News. 2(6):6-9.

Nair, K. K. 1968. A preliminary bibliography of the grass carp
Ctenopharyngodon idella Valenciennes. FAQ Fish. Cir. 302:1-15.

Cagni, J. E., D. L. Sutton, and R. D. Blackburn. 1971. The white amur
for aquatic weed control. Florida Agric. Exp. Sta. Jour. Ser. No.
3820. 19 p.

61


bacterium capable of causing disease in the water hyacinth.

Control of Fish

The control of fish pathogens has been emphasized in fish management
Programs, but they have not been evaluated in terms of lake restoration (17).
There are more outbreaks of bacterial diseases in fish in enriched than
unenriched waters (441), a potential control situation which might be ex-
ploited. Shapiro (442) proposed using specific diseases against zooplankti-
vorous fish to increase zooplankton numbers for phytoplankton control.

FUNGI

Control of Phytoplankton

Fungal parasites of phytoplankton may delay or decrease the maximum size
of the population; parasitism may also lower the development of one species
with respect to another (443). Differences in the composition or amount of
organic substances liberated by algae was suggested as a factor in the dif-
ferences in susceptibility of members of an algal population to fungal in-
fection (444). Safferman and Morris (445) determined that about 20 percent
of over 500 studied actinomycetes and fungal isolates were antagonistic
toward algae. A number of aquatic fungi parasitic on phytoplankton (446,
447, 448, 449) and diatoms (450, 451) have also been described.

Although a number of species of fungi have been listed as parasites of
the blue-green algae Anabaena, Aphanizomenon, Gomphosphaeria, Lyngbya,
Microcystis, and Oscillatoria, the possibility of their use has apparently
not been explored (443, 452, 453). The association and physiological rela-
tionships between fungi and blue-greens, however, have been reviewed by
Whitton (429).

Control of Macrophytes

A number of fungi have been identified as potential macrophyte controls,
primarily for water hyacinth and hydrilla. So far, thirty species have been
listed in a University of Florida project to survey, isolate, identify. test
and catalog all fungi associated with the water hyacinth (454).

The fungus Rhizoctonia solani, first isolated from the anchoring hya-
cinth (Eichhornia azurea) in Panama, is highly pathogenic to the water hya-
cinth (378, 455). R. solani occurs commonly in Central America and the
Caribbean, but not in the United States (456). It has been isolated also
from India (377). This fungus is highly virulent (457); the disease, which
causes severe blighting, proceeds optimally at 22-27 C (378). The RhEa
strain of R. solani is particularly pathogenic to water hyacinth but exten-
sive testing is still required (458).

Acremonium zonatum (=Cephalosporium zonatum) has been isolated from £1
Salvador, Panama, Puerto Rico, Florida, Louisiana and India. This fungus is

39


431.

432.

433.

434.

435.

436.

437.

438.

439.

440.

441.

442.

443.

Burnham, J. C. 1974. Bacterial control of aquatic algal populations.
Medical College of Ohio, School of Medicine, Toledo, Ohio. Notice
of Research Project, Smithsonian Science Information Exchange,
Washington, D. C. SIE No. GUW-4008.

Burnham, J. C. and T. Stetak. 1972. Observations on the interaction of
Bdellovibrio bacteriovorus with two species of blue-green algae.
Ann. Meet. Am. Soc. Microbiol. 72:33 (Abstr. G78).

Burnham, J. C., D. Sun, and T. Stetak. 1974. Biological properties of
a Bdellovibrio produced inhibitor of blue-green algae. Ann. Meet.
Am. Soc. Microbio. 74:62. (Abstr. G255).

Burnham, J. C. 1973. Bacterial control of aquatic algae. Ohio State
Univ. Columbus, Water Resources Center. 100 p. (NTIS PB-236
185/5GA)

Shilo, M. 1970. Lysis of blue-green algae by a myxobacter. J. Bacter-
jol. 104:453-461.

Daft, M. J. and W. D. P. Stewart. 1971. Bacterial pathogens of
freshwater blue-green algae. New Phytol. 70(5):819-829.

Schwabe, G. H. and 8B. Mollenhauer. 1967. Effect of accompanying bac-
teria on the thallus of Nostoc sphaericum. Nova Hedwigia. 13(1/2):
77-80. (in German) (Bio. Abstr. 49:91349)

Daft, M. J. and W. D. P. Stewart. 1973. Light and electron microscope
observation on algal lysis by bacterium CP-1. New Phytol. 72(4):
799-808.

Stewart, J. R. and R. M. Brown, Jr. 1969. Cytophaga that kills or
lyses algae. Science 164:1523-1524.

Mitchell, R. 1971. Role of predators in the reversal of imbalances in
microbial ecosystems. Nature 230:257-258.

Collins, V. G. 1970. Recent studies of bacterial pathogens of fresh-
water fish. J. Soc. Water Treat. Exam, 19:3-31.

Shapiro, J. 1975. Biomanipulation - an ecosystem approach to lake
restoration. Research proposal to U. S. Environmental Protection

Agency.
Canter, H. M. and J. W. G. Lund. 1951, Studies on plankton parasites.

III. Examples of the interaction between parasitism and other
factors determining the growth of diatoms. Ann. Bot., London N. S.

15:359:371.

81


Some good earlier reviews of biological control practices and princi-
ples (7, 13, 14) have been followed recently by a review of the biological
control of aquatic weeds (15), a bibliography with abstracts on biological
control (16) and a review of biological control and its relationship to lake

restoration (17).


FOREWORD

Effective regulatory and enforcement actions by the Environmental Protection
Agency would be virtually impossible without sound scientific data on pollu-
tants and thier impact on environmental stability and human health. Respon-
sibility for building this data base has: been assigned to EPA's Office of
Research and Development and its 15 major field installations, one of which
is the Corvallis Environmental Research Laboratory, (CERL).

The primary mission of the Corvallis Laboratory is research on the effects of
environmental pollutants on terrestrial, freshwater, and marine ecosystems;
the behavior, effects and control of pollutants in lake systems; and the
development of predictive models on the movement of pollutants in the bio-
sphere.

This report reviews biological methods commonly in use or proposed to control
the manifestations of excess nutrients in aquatic ecosystems. Such methodo-
logy in many cases may bring about the economical and full utilization of
these nutrients to the best advantage of the environment and man.

A. F. Bartsch
Director, CERL

iii


9€

TABLE 2. BLUE-GREEN ALGAL VIRUSES*

Virus Host Algae Reference Virus Host Algae Reference
A-1 Anabaena variablis 380 Lpp-1* Lyngbya.
: Plectonema
A-4(L) Anabaena variabilis 381 Phormidium 379
AC-1 Anacystis nidulans LPP-2 Lynabya
Chroococcus minor 382 ectonema
Phormi dium, 388
AP-1 Aphanizomenon flos-aquae 383 LPP-16 Plectonema 389
AR-1 Anabaenopsis ra
Anabaenopsis N-1 Nostoc muscorum 390
Raphidiopsis 384
S-1 Synechococcus strain NRC-1 391
AS-1 Anacystis nidulans ‘SAM-1 Synechococcus cedrorum
Synechoccus cedrorum 385 Anacystis nidulans
Microcystis. 392
c-1 Cylindospermum 384
o-1 Lyngbya
Plectonema SM-1 Synechococus elongatus
Phormi dium 386 Microcystis aeruginosa 393
enti" Lyngbya Unnamed Plectonema boryanum 394
Plectonema Unnamed Anabaena variabilis 395
Phormidium 387
Unnamed Microcystis aeruginosa
Wicrocystis: pulverea
Microcystis musicola 396

* Modified from Dunst et al. (17) and Cannon (391), with additions.

+ Probably same virus.


243.

244.

245,

246.

247,

248.

249,

250.

251.

252.
253.

254.

255.

Mitzner, L. 1974. Evaluation of biological control of nuisance aquatic
vegetation by white amur, Ctenopharygodon idella (Valenciennes).
Project No. F-88-R-1. Fisheries Section, Towa Conservation Comm.

Shleser, R. A. and R. R. Yeo. 1975. Biological control of aquatic
weeds using the herbivorous fish white amur. Univ. of Calif.,
Agricultural Experiment Station, Davis. Notice of Reserach Project,
Ree omat oc tence Information Exchange, Washington, D.C. SIE
lo. GY- .

Benn, B. 0. and W. N. Rushing. 1975. Aquatic plant control with the
white amur in Puerto Rico. U. S. Army Waterway Experiment Station,
Vicksburg, Miss. Notice of Research Project, Smithsonian Science
Information Exchange, Washington, D. C. SIE No. ZTK~653.

Ahling, 8. 1972. Grdaskarpsférsbket i Osbysjén. Institutet for Vat-
ten-och Luftvards-forskning, B-publ. 143. 27 p.

Swedish Water and Air Pollution Research Laboratory. 1973. Weed
control with grass carp in Sweden. IVL Bull, 2(2):9-11.

Zarnecki, S. 1968. Algae and fish relationships. p. 459-477. In
Jackson, D. F. (ed.) Algae, man, and the environment. Proc.
Intern. Symp., Syracuse Univ., June 18-30, 1967.

Lupacheva, L. I. and R. A. Baltadzhi. 1971. A study of the higher
aquatic vegetation of the coolant-reservoir of the Mironov-Skaya
Gres (Thermal power station) in relation to stocking with herbi-
vorous fish. (Sport Fish. Abstr. 18(2):142, No. 16082)

Nikolskii, C. V., V. V. Verigin, A. P. Makeeva, and G. V. Popova. 1968.
Investigating herbivorous fish and their introduction for fish

farming and for cleaning reservoirs. (Weed Abstr. 19:245, No.
1611)

Hickling, C. F. 1965. Biological control of aquatic vegetation. Pest
Articles and News Summaries 11:237-244,

Nature. 1968. Clearance by carp. 222(5165):322-323.

Philipose, M. T. 1968. Present trends in the contro] of weeds in fish
culture of Asia and the Far East. FAO Fish. Rep. 44(5):26-52.

Ahmad, N. 1968. Review of research work done by the Directorate of
Fisheries, West Pakistan, Agr. Pakistan 19(3):557-527.

Food and Agriculture Organization of the United Nations. 1972. Control
of aquatic weeds. FAO Aquaculture Bull. 4(2):6-7.

67


368.

369.

370.

371.

372.
373.

374,

375.

376.

377.

378.

379,

380.

Gammon, J. R. and A. D. Hasler. 1965. Predation by introduced muskel-
lunge on perch and bass, I: Year 1-5. Wis. Acad. Sci., Arts and
Lett. 54:249-272.

Jenkins, R. M. 1970. Reservoir fish management. p. 173-182. In A
century of fisheries in North America. Amer. Fish. Soc. Spec.
Publ. No. 7.

McCarraher, D. B. 1959. The northern pike-bluegill combination in
north-central Nebraska farm ponds. Prog. Fish Cult. 21(3):188-189.

Powell, T. G. 1973. Effect of northern pike introductions on an over-
abundant crappie population. Colorado Divison of Wildlife. Colo-
rado F-34-4, Spec. Rep. 31.

Sport Fishing Institute. 1961. Stocking story. SFI Bull. 115:7.

Ryder, R. A. 1970. Major advances in fisheries management in North
American glacial lakes. p. 115-127. In A century of fisheries in
North America. Amer. Fish Soc. Spec. Publ. 7.

Bennett, G. W. 1971. Management of artificial lakes and ponds. 2nd ed.
Van Nostrand Reinhold Company. 375 p.

Pirozhnikov, P. L., A. F. Karpevich, A. J. Isayev, and Y. I. Karpova.
1969. Biological principles for improving fisheries in inland
waters. Problems of Ichthyol. Amer. Fish. Soc. 9(5):744-751.

Zettler, F. W. and T. W. Freeman. 1972. Plant pathogens as biological
controls of aquatic weeds. Ann. Rev. of Phytopathol. 10:455-470.

Freeman, T. E., R. Charudattan, F. W. Zettler, R. E. Rintz, H. R. Hill,
B. Joyner, and H. F. Hayslip. 1973. Biological control of water
weeds with plant pathogens. Florida Water Resources Res. Center,
Gainesville. Publ. 23. 52 p.

Freeman, T. E. and F. W. Zettler. 1974. A disease of water hyacinth
with biological control potential. p. C-3. In Gangstad, E. 0., T.
E. Freeman, F. W. Zettler, R. E. Rintz, R. Charudattan, K. Conway,
and H. E. Hill. Aquatic weed control with plant pathogens. Aqua-
tic Plant Control Program. Tech. Rep. No. 8. Army Eng. Waterways
Exp. Sta., Vicksburg, Miss.

Safferman, R. S. and M. E. Morris. 1963. Algal virus: isolation.
Science 140:679-680.

Kozyakov, S., B. Gromov, and I. Khudvakov. 1972. A-1 (L)

cyanophage of the blue-green alga Anabaena variabilis. Mikrobolog-
jya 41:555-559. (Translation)

76


EPA-600/3-77-084 :
July 1977 Ecological Research Series

BIOLOGICAL CONTROL OF AQUATIC
NUISANCES - A REVIEW

Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Corvallis, Oregon 97330


DISCLAIMER

This report has been reviewed by the Corvallis Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Mention of trade names or commercial products does not
constitute endorsement or recommendation for use.

ii


The amur exhibits a negative nitrogen balance when fed elodea, suggesting
a necessity for a food with a higher protein content, or for supplemental
protein, for normal growth (191, 225, 226). A Chinese study on digestibility
concluded that animal materials and the plant Wolffia arrhiza are the most
suitable food of the amur once it reaches the vegetation consuming stage
(227). It increases nutrient cycling by excreting 50-75 percent of the
ingested phosphorus and 90-95 percent of the nitrogen (225).

Protein and caloric differences in aquatic plants result in contrasting
conversions of plant material into fish flesh; while 48 g (fresh weight) of
hydrilla were required for a 1.0 g weight gain, only 22 g of duckweed were
required for the same increase (115). Amur similarly gained less weight on a
diet of water hyacinth than on hydrilla and southern naiad (228).

Stocking rates--Most stocking rates reported are for ponds and indicate
a variety of combinations of numbers, lengths, weights, and age per unit
area. Blackburn (229) emphasized dependence of stocking rates on the rela-
tionships between fish size and amount and type of vegetation rather than on
a standard rate. The size of the fish available, how long control is desired
and the relative palatability of the aquatic weeds present are also important
considerations (230).

Pond stocking rates in the United States for amur of unreported size
have ranged from 49 to 99 fish/ha (40, 199, 231). Fish 15-40 cm long have
been stocked at 49-1690/ha in ponds and pools (61, 211, 232). Amur weighing
0.9 kg have been stocked at 247 fish/ha (60).

Stocking rates used or recommended in Russia ranged from 36-86 fish/ha
(233), to 400-500 fingerlings or two-year olds/ha (234). Seventy-nine kg/ha
of one-year fish have cleared ponds of vegetation (235) and 254 kg/ha were
used in canals (236). Recommended rates in Czechoslovakian ponds ranged from
2,000 one-year fish to 150 four-year fish/ha (50, 237, 238). Effective
stocking rates in India ranged from 654 to 5,200/ha for fish initially weighing
62-2,640 g (215). Rates for English ponds have been reported at 92-300 kg/ha
(239, 240). One hundred twenty-five to 250 kg/ha of two-year fish were also
suggested as sufficient to reduce aquatic weeds by half (241).

Stocking rates reported for control of specific weeds are variable.
Hydrilla and southern naiad were controlled by 309 amur/ha (115); rates
greater than 49/ha were recommended for heavy hydrilla infestations (229).
Water hyacinth might be controlled by 99 amur/ha if assisted by a winterkill
and herbicides (176). Naiad and duckweed were controlled at a stocking
rate of 136 fingerlings/ha, but not at 69/ha (191).

Use in United States--The State of Arkansas has actively used the amur
in a program of aquatic weed control and has recommended its use from eco-
logical, fisheries and economic standpoints (174, 180, 242).

Baiiey (198) recently summarized its use there, where more than 100 lakes
totaling over 20,250 ha have been stocked with 308,000 amur. The fish
effectively controls 22 genera of aquatic macrophytes but is ineffective

24


456.

457.

458,

459.

460.

461.

462.

463.

464.

465.

Rintz, R. E. and R. Charudattan. 1974. A survey for diseases of water
hyacinth in Puerto Rico. p. H3-H4. In Gangstad, E. 0., T. E.
Freeman, F. W. Conway, and H. E. Hill. Aquatic weed control with
Plant pathogens. Aquatic Plant Control Program. Tech. Rep. 8.
Army Eng. Waterways Exp. Sta., Vicksburg, Miss.

Rintz, R. E. 1973. Location, identification and characterization of
Pathogens of the water hyacinth. Ph.D Thesis. Univ. of Florida.
(NTIS PB-223 868)

Joyner, B. G. and T. E. Freeman. 1973. Pathogenicity of Rhizoctonia
solani to aquatic plants. Phytopathology 63(6):681-685.

Rintz, R. E. 1973, A zonal leaf spot of water hyacinth caused by
Cephalosporium zonatum. Hyacinth Control J. 11:41-44.

Zettler, F. W., T. E. Freeman, and A. A. Cook. 1975. Biological con-
trol of water weeds with plant pathogens. Univ. of Florida, Agri.
Exp. Sta., Gainesville. Notice of Research Project, Smithsonian
Science Information Exchange, Washington, D. C. SIE No. GY 57699-
1.

Freeman, T. E., R. Charudattan, and K. Conway. 1974. Exploration,
pathogenicity, and integrated control. p. I3-I9. In Gangstad, E.
0., T. E. Freeman, F. W. Zettler, R. E. Rintz, R. Charudattan, Kk.
Conway, and H. E. Hill. Aquatic weed control with plant pathogens.
Aquatic Plant Control Program. Tech Rep. 8. Army Eng. Waterways
Exp. Sta., Vicksburg, Miss.

Charudattan, R. 1975. Use of plant pathogens for control of aquatic
weeds. p. 127-144. In Bourquin, A. W., D. G. Ahearn, and S. P.
Meyers (eds.) Impact of the use of micro-organisms on the aquatic
environment. U. S. Environmental Protection Agency, Ecol. Res.
Ser. 660/3-75-001.

Charudattan, R., G. Allen, and G. E. Templeton. 1975. Plant pathogens
for control of aquatic weeds: Summary. p. 247-248. In Bourquin,
A. W., D. G. Ahearn, and S. P. Meyers (eds.) Impact of the use of
micro-organisms on the aquatic environment. U. S. Environmental
Protection Agency. Ecol. Res. Ser. 660/3-75-001.

Nag Raj, T. R. and K. M. Ponnappa. 1970. Blight of water hyacinth
caused by Alternaria eichhornia sp.nov. Trans. Brit. Mycol. Soc.

55(1) :123-130.
Cappleman, L. E. 1972. Detached leaf culture of Eichhornia crassipes

and application to the culture of its pathogens. M.S. Thesis,
Florida Atlantic Univ., Boca Raton, Florida.

83


394.

395.

396.

397.

398.

399.

400.

401.

402.

403.

404,

405.

406.

407.

Singh, P. K. 1974. Isolation and characterization of a new virus
infecting the blue-green alga Plectonema boryanum. Virology 58:
586.

Granhall, U. and A. V. Holsten. 1969. The ultrastructure of a
cyanophage attack on Anabaena variabilis. Physiol. Plantarum
22:713-722.

Goryushin, V. A. and S. M. Chaplinskaya. 1966. Existence of viruses of
blue-green algae. Mikrobiol. Zh. Akad. Nauk. Ukr. RSR 28:94-97.
(English Summary) .

Padan, E. and M. Shilo. 1968. Spread of viruses attacking
blue-green algae in freshwater ponds and their interaction with
Plectonema boryanum. Bamidgeh 20:77-87.

Padan, E. amd M. Shilo. 1969. Distribution of cyanophages in natural
habitats. Verh. Int. Verein. Limnol. 17:747-751.

Padan, E. and M. Shilo. 1973. Cyanophages - viruses attacking blue-
green algae. Bacteriol. Reviews 37:343-370.

Shane, M. S. 1971. Distribution of blue-green algal viruses in various
types of natural waters. Water Res. 5:711-716.

Jackson, D. and V. Sladecek. Algal viruses - eutrophication control
potential. Yale Sci. Maga. 44:16-21.

Brown, R. M., Jr. 1972. Algal viruses. Advanced Virus Res. 17:243-
277.

Safferman, R. S. 1973. Phycoviruses. p. 214-237. In Carr, N. G. and
B. A. Whitton (eds.) The biology of blue-green algae. Blackwell
Sci. Pub., Oxford.

Cannon, R. 1975, Field and ecological studies on blue-green algal
viruses. p. 112-117. In Brezonik, P. L. and J. L. Fox (eds.)
Proc. symp. on water quality management through biological control.
University of Florida and U. S. Environmental Protection Agency,
Gainesville, Jan. 29-31.

Cannon, R. E., M. S. Shane, and E. DeMichele. 1974. Ecology of blue-
green algal viruses. Proc. Am. Soc. Civil Eng. J. Envir. Eng. Div.
100(EE6) :1205-1211.

Safferman, R. S. and M. E. Morris. 1974. Bibliography-phycoviruses.
National Environmental Research Center, Environmental Protection
Agency, Cincinnati, Ohio.

Shilo, M. 1972. The ecology of cyanophages. Bamidgeh 24:76-82.

78


TABLE 1 (continued)

Problem or Project

Solution or Proposed Treatment Location Results or Remarks References
Alligator weed Flea beetle-Agasicles Florida Most effective, consumed exten- 95, 103
sive areas; severe damage when 104, 105
54-108 adults/m2
Stemborer-Vogtia N. Carolina to Very promising control 104, 105,
Florida 131
Salvinia Moth-Samea, Grasshopper-Paul ina Africa Results uncertain in Kariba Lake 79
Excessive vegetation Crayfish-Orconectes causyi New Mexico Successfully cleared several 169
lakes
Crayfish-Orconectes causyi S. Dakota Control in reservoir not 170
documented
Crayfish-Pacifasticus Washington Results inconclusive in
Crayfish-Spp. Wisconsin Not recommended 172
o Need infested White amur (Ctenopharyngodon Sweden Myriophyllum decreased to half 201, 202
akes and ponds idella) the amount present in previous
year in Lake Osbyjon
White amur (Ctenopharyngodon Arkansas Amur effective in controlling 198
idella) weeds, generally stocked at 25
—— 20-25 cm fish/ha; stocked in
over 100 lakes
White amur (Ctenopharyngodon Towa Reduced standing crop of aquatic 243
idela) ° weeds by half in Red Haw Lake
White amur (Ctenopharyngodon Alabama Controlled weeds in ponds 49, 61, 211
idella)
White amur (Ctenopharyngodon U.S.A. Uncertainty of effect of intro- 181, 185, 268, 270,

idella)

duction a disadvantage.
Banned in many states.

281, 282, 287

(continued)


10.

VW.

12.

13.

14,

15.

16.

17.

18.

20.

al.

22.

Perkins, B. D. 1973. Potential for water hyacinth management with
biological agents. p. 53-64. In Tall Timbers conference on
ecological animal control by habitat management. No. 4.

Crowder, J. P. 1974. Exotic pest plants of South Florida. Dep. of the
Interior, Atlanta, Ga. South Florida Environmental Proj. 51 p.
(NTIS PB-231 619/8).

Brezonik, P. L. and J. L. Fox (eds.) 1975. Water quality management
through biological control. Proc. Symp., University of Florida and
U. S. Environmental Protection Agency, Gainesville, Jan. 29-31.
164 p.

National Academy of Sciences. 1968. Principles of plant and animal
pest control, Vol. 2. Weed Control. Publ. No. 1597. 250 p.

Holm, L. G., L. W. Weldon, and R. D. Blackburn. 1969. Aquatic weeds.
Science 166:699-709.

Andres, L. A. and F. D. Bennett. 1975. Biological control of aquatic
weeds. Ann. Rev. Entomol. 20:31-46.

Harrison, E. A. 1975. Aquatic weed control. (A bibliography with
abstracts). Nat. Tech. Information Service. (NTIS PS-75/581/9GA).

Dunst, R. C., S. M. Born, P. D. Uttormark, S. A. Smith, S. A. Nichols,
J. A. Peterson, D. 0. Knauer, S. L. Serns, D. R. Winter and T. L.
With. 1974. Survey of lake rehabilitation techniques and experi-
ences. Tech. Bull. No. 75. Dep. of Natur. Resources, Madison,
Wis. 179 p.

Canter, J. M. and J. W. G. Lund. 1968. The importance of protozoa in
controlling the abundance of planktonic algae in lakes. Proc.
Linnean Soc. London. 179(2):203-219.

Ho, T. S. and M. Alexander. 1974. The feeding of amebae on algae in
culture. J. Phycol. 10(1):95-100.

Cook, W. L., D. G. Ahearn, D. J. Reinhardt, and R. J. Reiber. 1974.
Blooms of an algophorous amoeba associated with Anabaena in a fresh
water lake. Water, Air, and Soil Pollution 3(1974):71-80.

Ahearn, D. G. 1975. (Discussion). p. 123. In Bourguin, A. W., D. G.
Ahearn, and S. P. Meyers (eds.) Impact of the use of microorganisms
on the aquatic environment. U. S. Environmental Protection Agency.
Ecol. Res. Ser. EPA 660/3-75-001.

Cole, G. T. and M. J. Wynne. 1973. Endocystis of Microcystis aerugino-
sa by Ochromonas dancia. p. 127-166. In Prows, B. L. and W. F.
McIlhenny. Development of a selective algaecide to control nui-
sance algal growth. U. S. Environmental Protection Agency. Ecol.
Res. Ser. EPA 660/3-73-006.

48


TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)

7, REPORT NO. 2. 3. RECIPIENT’S ACCESSION'NO.
EPA-600/3-77-084
4. TITLE ANDO SUBTITLE 5. REPORT DATE
duly 1977
Biological Control of Aquatic Nuisances - A Review Is. PERFORMING ORGANIZATION CODE
7. AUTHOR(S) I8. PERFORMING ORGANIZATION REPORT NO.

Gerald S. Schuytema

I9. PERFORMING ORGANIZATION NAME AND ADDRESS: 10. PROGRAM ELEMENT NO.
Environmental Research Laboratory-Corvallis, OR 1BA031
Office of Research and Development TT. CONTRACT/GRANT NO.

U. S. Environmental Protection Agency
Corvallis, OR 97330

12, SPONSORING AGENCY NAME AND ADDRESS. 13. TYPE OF REPORT AND PERIOD COVERED
Final
same 14. SPONSORING AGENCY CODE
EPA/600/02

715. SUPPLEMENTARY NOTES

16, ABSTRACT
A total of 532 references on the biological control of aquatic nuisances were
reviewed. Three major control approaches exist. Grazing and predation have been
the most frequently utilized techniques, with emphasis on macrophyte control by
fish and insects. The use of pathogens is potentially effective, with most promise
in macrophyte control. Biomanipulation, the exploitation of the interrelationships
among plants and their environment is a most promising technique for eutrophic
systems. This approach includes increasing algal grazers while controlling zoo-
planktivores and exploiting the competitive and growth limiting reactions among
various species. The importance of using host-specific organisms to prevent damage
to desirable components of the ecosystem is emphasized.

17. KEY WORDS AND DOCUMENT ANALYSIS.
ja. DESCRIPTORS b.IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Aquatic weeds* Inhibition Biological Control* 06/C
Reviews * Fishes Eutrophication* 08/H
Cyanophyta* Insects Biomanipulation*
Viruses Snails Water hyacinth
Fungi Phytoplankton Alligator weed
Bacteria Zooplankton Agasicles
Competition Neochetina
18. DISTRIBUTION STATEMENT hte Ais Tapia 21. NO. OF PAGES
. Unclassified
Release to public 20. SECURITY CLASS (This page] ware
Unclassified

EPA Form 2220-1 (9-73)
90 # U.S, GOVERNMENT PRINTING OFFICE: 1977~798-537/203 REGION 10



269.

270.

271.

272.

273.

274,

275.

276.

277.

278.

279.

280.

281.

282,

Sport Fishing Institute. 1975. Exotic fishes in United States waters.
SFI Bull. 264:1-4.

Pelzman, R. J. 1971. The grass carp. California Department of Fish
and Game. Inland Fisheries Administrative Rep. No. 71-14. 8 p.

Sport ersning Institute. 1972. White amur (grass carp). SFI Bull.

Alabaster, J. S., and B. Stott. 1967. Grass carp for aquatic weed
sore 36 Symp. Internationales Wasserpflanzen, Oldenburg, Germany.

Inaba, D., M. Nomura, and M. Nakamura. 1957. Preliminary report on the
spawning of grass-carp and silver carp in the Tone River, and
development of their eggs. J. Tokyo Univ. Fish. 43:86-96.

Sport Fishing Institute. 1975. North American reproduction of grass
carp. SFI Bull. 269:5.

Sport Fishing Institute. 1976. Status of grass carp. SFI Bull.
24-6.

Marking, L. L. 1972. Sensitivity of the white amur to fish
toxicants. Prog. Fish Cult. 34(1):26.

Cumming, K. B., R. M. Burress, and P. A. Gilderhus. 1975. Controlling
grass carp (Ctenopharyngodon idella) with antimycin, rotenone, and
thanite and by electrofishing. Prog. Fish Cult. 37(2):81-84.

Willey, R. G., M. J. Doskocil, and C. A. Lembi. 1974. Potential of

the white amur (Ctenopharyngodon idella Val.) as a biological
control for aquatic weeds in Indiana. Proc. Indiana Acad. Sci.

83:173-178.

Babayan, K. E. 1966. A new stage in the culture of plant-
eating fishes. (Trans]. from Russian) 8 p. Fisheries Research
Board of Canada Translation Series No. 714.

Terrell, T. T. 1975. The impact of macrophyte control by the white

amur (Ctenopharyngodon idella). Verh. Int. Verein. Limnol. 19:
2510-2514.

Cross, D. G. 1970. The tolerance of grass carp (Ctenopharyngodon
idella Val.) to sea water, J. Fish Biol. 2:231-233.

Courtenay, W. R., Jr. and C. R. Robins. 1975. Exotic organisms: an
unsolved, complex problem. BioScience. 25(5):306-373.

69


protein (196).

Lamarra (318) found that carp could regenerate phosphorus from the
sediments as a result of digestion, and suggested that a carp population of
200 kg/ha could internally load a lake with orthophosphate at 0.52 mg P/m2/
day. This phosphorus regeneration which might result in increased phyto-
plankton growth should be considered if bottom feeding fish such as carp are
proposed for aquatic plant control.

Israeli carp (the Israel strain of the common carp) controlled certain
rooted aquatics in Arkansas when stocked at the rate of 124 0.23 kg fish/ha
(60). It also controlled coontail and elodea in a 1,215 ha Arkansas reser-
voir when about 9,980 kg of fish were stocked over 3 years (319).

Others --

Silver dollar fish (Metynnis roosevelti and Mylossoma argentum), native
to South America, showed Some potential in submersed plant control in Cal-
ifornia by readily grazing upon a variety of pondweeds. Grazing was much
reduced below 21 C and death occurred below 15.6 C, hence utilization in
(Saye regions would necessitate holding the fish overwinter in warm water

320).

The gouramy (Osphronemus gorami) has been considered useful in con-
trolling some submerged macrophytes in Asian ponds and reservoirs, but it is
not as effective as tilapia (253). The tawes, (Puntius javicans) effective
in weed control experiments in East Pakistan (165), is utilized in Indonesia
and a few south Asian countries for the dual purpose of fish production and
weed control (253).

Although the channel catfish consumes higher plants, it, along with the
goldfish (Carassius auratus) is considered to have little potential for
controlling aquatic weeds (40, 61).

Fowl

Domestic ducks can remove small amounts of vegetation and can be ef-
fective in floating weed control (14, 321) but human predation limits their
usefulness (37). They have been used in aquatic weed control experiments in
East Pakistan (165) and have been recommended in Asian countries where other
suitable biological control agents are not available (253).

Muscovy ducks (Cairina moschata), stocked at 25/ha, have controlled
duckweed in some Louisiana ponds (322). In Georgia, 15/ha required 2 to 11
months to achieve complete reduction on 0.3 to 0.4 ha ponds (58). These
ducks were also considered to be potentially useful as biological controls
in Guyana (73).

Semi-wild mallard ducks (Anas platyrhynchos) kept dairy drain lagoons
free of aquatic grasses; natural breeding was sufficient to maintain the duck
populations (323).

30


crop of attached filamentous green algae in small lakes. They may trigger an
annual succession with widespread consequences, since factors which affect
the periphyton community of a small lake may affect its entire energy budget
(476). By overgrazing, they can also depress primary productivity and alter
community metabolism, in addition to decreasing the relative volume of blue-
green algae (477). Wassersug (478) documented the transport of nutrients
from the aquatic to the terrestrial environment by frogs and toads and con-
cluded that these organisms were important in the removal of nutrients from
aquatic systems. Results of current studies on the role of tadpoles in the
regulation of algal productivity will be used to model their impact on var-
ious physico-chemical components of the aquatic community (479). The rela-
tionships of tadpoles and their environment may thus suggest potential bio-
manipulative schemes to attain more desirable aquatic communities. Since
they are preyed upon heavily by fish, tadpoles probably would not be an
important control factor in large lakes.

FISH STOCKING

Reducing algal populations by stimulating increases in algae-feeding
fish has been recommended as a means of long-term eutrophication control in
established reservoirs (480). The somewhat different approach of introducing
carnivorous fish to prey upon zooplanktivorous fish was suggested by Shapiro
et al. (27). This induces an increase in grazing zooplankton able to reduce
phytoplankton populations. He demonstrated this concept in pilot scale
enclosures and ponds, and has now proceeded to full scale experimentation in
several Minnesota lakes (481, 482).

FISH STERILIZATION AND HYBRIDIZATION

Sterilization and sex reversal in fish have been used in fish culture,
and may have application in the control or manipulation of undesirable spe-
cies in eutrophic systems. Sterilization, believed to have only limited
promise as a biological control measure (369), may be induced by hormone
injection or hybridization (193). Blue-gills (Lepomis macrochirus) have been
sterilized by sub-lethal doses of gamma radiation (1000 R) in experiments on
population control (483). Male fertility in guppies (Lebistes reticulatus)
was adversely affected by TEPA [tris (l-aziridinyl) phosphine oxide], an
insect chemosterilant (484). Use of methyltestosterone to produce sex re-
versal and resultant monosex populations of bluegills was generally unsuc-
cessful (485).

Fish hybridization is an important aspect of fish culture (486, 487,
488) since the process can combine the desirable attributes of the parent
stock and may result in a fish with superior qualities (193). This technique
however, has had limited application in biological control programs. Sterile
or monosex hybrids would have advantages over stocking fertile fish when
reproduction is not desired (489). For instance, research is being conducted
on developing sterile hybrids of Tilapia to control macrophytes (490). Hy-
bridization might also be useful in biological control situations where
improved predation is desirable. For example a white bass (Roccus chrysops)-

42


REFERENCES

Mulligan, H. G. 1969. Management of aquatic vascular plants and
algae. p. 464-482, In Eutrophication: Causes, consequences
and correctives. Nat. Acad. Sci., Washington, D. C.

World Farming. 1972. Turning the tide against aquatic weeds.
World Farming 14(9):18-22. (WRSIC Abstr. W73-07193)

Agricultural Research Service. 1971. Managing our environment.
Agr. Inf. Bull. No. 351. 48 p.

Army Engineer District, Jacksonville, Fla. 1973. Aquatic plant
control program. State of Florida (Final Environmental
Impact Statement) 201 p. (NTIS EIS-FL~73-1488-F)

Martin, D. F., M. T. Doig, and D. K. Millard. 1971. Potential
control of Florida elodea by nutrient-control agents.
Hyacinth Control J. 9(1):36-39.

Boyter, C. J., and M. P. Wanielista. 1973. Review of lake
restoration procedures. Water Resources Bull. 9(3):499-
511.

Blackburn, R. D., D. L. Sutton and T. Taylor. 1971. Biological control
of aquatic weeds. J. Irrigation and Drainage Div., ASCE, 97(IR3):

421-432.

Coulson, J. R. 1974. Potential environmental effects of the
introduction of the Argentine water hyacinth weevil,
Neochetina eichhorniae, into the United States. p. F3-F15.
In Gangstad, E. 0., J. J. Raynes, C. R. Zeiger, J. M.
Tngersoll, R. D. Gordon, et al. Biological control of water
hyacinth with insect enemies. Aquatic Plant Control Program,
Tech. Rep. No. 6. Army Eng. Waterways Exp. Sta., Vicksburg,

Miss. (NTIS AD-775 408/8).

Sailer, R. I. 1975. Principles and techniques of biological
control. p. 8-14. In Brezonik, P. L. and J. L. Fox (eds.)
Proc. symp. on water quality management through biological
control. Univ. of Florida and U. S. Environmental Protection

Agency, Gainesville, Jan. 29-31.

47


striped bass (Roccus saxatilus) hybrid was developed to produce an effective
predator and control of the gizzard shad (Dorosoma cepedianum) (491, 492).

FERTILIZATION

Artificial fertilization to induce shading by phytoplankton has long
been reported as an effective control of aquatic macrophytes (493, 494, 495,
496). The increased phytoplankton growths and subsequent decrease in trans-
parency may be sufficiently objectionable, however, to preclude this as an
acceptable practice. Recent evaluations of fertilization as a method of
controlling higher aquatic plants in farm ponds and small lakes in Michigan
have been undertaken by McNabb (497).

Fertilization with phosphate only has been satisfactory to maintain
control in many ponds (498). In some instances, superphosphates and mixed
commercial fertilizers reportedly caused blue-green algal blooms that re-
sulted in fish mortalities (499). For effective control, some ponds require
an average of 900-1,345 kg/ha or as much as 1,680 kg/ha each year of a fert-
ilizer such as 8-8-2 (N, P, K) (500).

Macrophytes were eliminated in an artificial 18 ha lake in New Jersey
after fertilization. Generally, 56 kg/ha of 5-10-5 inorganic fertilizer was
applied seven separate times the first year; the dosage was reduced by one-
half the following year using the same schedule (501, 502, 503). Similarly,
application of a fertilizer every 10-14 days in a 16 ha Kansas lake con-
trolled aquatic vegetation in depths greater than 1.5 m. Control was achieved
with a total of 347 kg/ha of ammonium sulfate (21-0-0) and 226 kg/ha of
triple superphosphate (0-46-0) (504).

Fertilization as a control practice yields variable results (505) and
may be responsible for winter and summer kills of fish (359). Fertilizers
are too expensive in some areas of southeast Asia for this method to be
practical; however, macrophytes have been controlled there in ponds fertilized
with sewage (253). In Pakistan, fertilization effectively prevented the
regeneration of macrophytes after their removal by hand (165). Some ecologi-
cal effects of shading were demonstrated in Lake Apopka, Florida (506).
Gizzard shad increased in this lake after persistant phytoplankton blooms
shaded out the pondweed, causing it to disappear. The shad then provided
forage for an increasing gamefish population but eventually became too large
and numerous, resulting in a decrease in the gamefish.

COMPETITION

Competition between aquatic plants can be utilized to eliminate or
control undesirable species. Slender spikerush (Eleocharis acicularis) is
competitive with certain rooted aquatic plants in California canals (507).
It can progressively eliminate a variety of other plants. Its capacity for
reproduction, mat-like growth form, competition for nutrients and cold-
hardiness are all critical factors in its ability to out-compete other
species (508, 509).


312.

313.

314.

315.

316.

317.

318.

319.

320.

321.

322.

323.

324.

325.

326.

Threinen, C. W. and W. T. Helm. 1954. Experiments and observations
designed to show carp destruction of aquatic vegetation. J. Wild-
life Manag. 18:247-251.

Tryon, C. A., Jr. 1954. The effect of carp enclosures on growth of
submerged aquatic vegetation in Pymatuning Lake, Penn. J. Wildlife
Manag. 18:251-254.

Lewis, W. M. 1974. Benthic feeding of common carp. FAQ Aquacult.
Bull. 6(2-3):6-7.

Black, J. D. 1946. Natures own weed killer - the German carp. Wis.
Conserv. Bull. 11:3-7.

King, D. R. and G. S. Hunt. 1967. Effect of carp on vegetation in a
Lake Erie marsh. J. Wildlife Manag. 31:181-188.

Wiackowski, S. K. 1971. Biological control of noxious plants. (Biol.
Abstr. 55(5):23461)

Lamarra, V. A., dr. 1975. Digestive activities of carp as a major
contributor to the nutrient loading of lakes. Verh. Int. Verein.
Limnol. 19:2461-2468.

Mathis, W. P. 1965. Observations on control of vegetation in Lake
Catherine using Israeli carp and a fall and winter drawdown. Proc.
Southeast. Ass. Game and Fish Comm. 19:197-205.

Yeo, R. R. 1967. Silver dollar fish for biological control of sub-
mersed aquatic weeds. Weeds 15:27-31.

Dillon, 0. W., dr. 1968. Aquatic weeds in farm and ranch waters.
Proc. Weed Sci. Soc. Amer. 8:40. (Abstr.)

Lapham, V- T. 1967. A new technique for duckweed control. Proc.
South. Weed Conf. 20:339-341.

Murray, W. D. 1969. Mosquito control with weed control. Proc. Calif.
Weed Conf. 21:40-42.

Ross, E. 1971. Biological control of pond weeds with white Chinese
geese. Hawaii Farm Sci. 20(2):11-12.

Van Deusen, R. D. 1972. Swan for your school pond. Sci. and Children
9(5):5 p.

Van Deusen, R. D. 1973. Ornamental allies. Swans control plants. The
Amer. Fish Farmer and World Aquacult. News. 4(2):4-6.

72


444,

445.

446.

447.

448,

449.

450.

451.

452.

453.

454.

455.

Masters, M. J. 1971. The ecology of Chytridium deltanum and other
fungus parasites on Oocystis spp. Can. J. Bot. 49(1):75-87.

Safferman, R. S. amd M. E. Morris. 1962. Evaluation of natural pro-
ducts for algicidal properties. Appl. Microbiol. 10:289-292.

Canter, H. M. 1950. Fungal parasites of the phytoplankton. I.
(Studies on British chytrids, X). Ann. Bot., London, N. S.
14: 263-289.

Canter, H. M. 1954. Fungal parasites of the phytoplankton. III.
(Studies on British chytrids, XIII) Proc. Brit. Mycol. Soc.
37:111-132.

Canter, J. M. 1971. Studies on British chytrids. XXXI. Rhizophydium
androdioctes sp. nov. parasitic on Dictyosphaerium pulchellum
Wood from the plankton. Trans. Brit. Mycol. Soc. 56(1):115-120.

Canter, H. M. 1973. On Zygorhizidium venustum (Canter) n. comb. to-
gether with an illustrated list of chytrids occurring on Chryso-
phycean algae. Nova Hedwigia 21:577-597.

Canter, H. M. and J. W. G. Lund. 1948. Studies on plankton parasites.
I. Fluctuations in numbers of Asterionella formosa Hass. in rela-
tion to fungal epidemics. New Phytol. 47:238-261.

Canter, J. M. and J. W. G. Lund. 1953. Studies on plankton parasites.
II. The parasitism of diatoms with special reference to lakes in
the English Lake District. Trans. Brit. Mycol. Soc. 36:13-37.

Canter, H. M. 1951. Fungal parasites of the phytoplankton II. (Studies
on British Chytrids, XII) Ann. Bot., London, N.S. 15:129-156.

Canter, H. M. 1973. A guide to the fungi occurring on planktonic blue-
green algae. p. 145-158. In Desikachary, T. V. (ed.) Taxonomy
and biology of blue-green algae. First Intern. Symp. on Taxon. and
Biol. of Blue-green Algae, Univ. of Madras, Madras, India.

Conway, K. E., T. E. Freeman, and R. Charudattan. 1974. The fungal
flora of water hyacinth in Florida. Florida Water Resources Re-
search Center Publ. No. 30. Florida Agri. Exp. Sta. J. Series No.
5519. 11 p.

Joyner, B. G. 1973. Characterization of a Rhizoctonia sp. pathogenic
to aquatic plants. Appendix A. In Gangstad, E. 0. Control of
aquatic plants with plant pathogens. Office of the Chief of
Engineers (Army), Washington, D. C. (NTIS AD-909 2862)

82


The interactions of blue-green algae and cyanophages are complex and
depend upon fluctuations in external conditions in addition to the properties
of the virus and algae. Temperature, ultra-violet radiation, and unbalanced
growth conditions influence viral development which in turn may be involved
in seasonal blue-green fluctuations (407). An amoeba, Hartmanella glebae, is
also involved with the interactions of the blue-green alga Plectonema boryanum
and LPP-1 cyanophage. There is evidence that the amoeba feeds on the alga
and may serve as a reservoir for the cyanophage (405).

The degree of control that viruses might actually exercise on natural
populations (403) was indicated by a case in which virus Ap-1 appeared to
regulate the termination of a bloom of Aphanizomenon flos-aquae (383).
Evidence for lysogeny, or the harboring by Plectonema boryanum of a cyanophage
capable of causing lysis, makes natural population control more reasonable,
according to Cannon et al. (408). Lysogeny induced by antibiotics, stress or
pollutants may also be involved in the natural control of some blue-green
algae (409, 410). Cannon (404) has suggested that the control of Plectonema
involves a choice by the virus to kill the cell or to integrate its chromo-
some with that of the host.

Although cyanophages have the potential for algae control (383, 395,
397, 401, 411, 412), their practical application is still an open question
(399) and further study is necessary (402). The only instance of actual
control as a management procedure appears in a Russian report concerning a
blue-green algal scum lysed by spray application of cyanophages (Topachevsky,
cited in 413). Kraus (414, pers. comm.) believed that while cyanophage-algal
relationships could indicate the eutrophic condition of the water, the resis-
tance of blue-green algal blooms to the already present cyanophage suggests
that the algae are actually scavenging the viruses from the water rather than
being controlled by them. Using cyanophages to control blue-green algae in
areas where there are temperate viruses (those which do not necessarily cause
lysing of the host) may be impractical as the temperate virus can immunize
the host against virulent forms (415). In order to prevent serious environ-
mental consequences, Cannon (404) urged that much careful work be conducted
before any attempt is made at viral regulation of natural populations.

Cannon (404) has pointed out many of the basic research needs in cyano-
phage research. These include understanding the chemical and biological
causes of algal blooms, characterization and isolation of additional cyano-
phages, and study of the host-parasite relationship at its most basic level.
Some recent work on cyanophages include research on a virus infecting Ana-
cystis nidulans (416), screening studies on the natural waters of New Jersey
for cyanophages (417), and a Nebraska study on naturally occurring viruses

for algal control (418).
Control of Other Algae

Viruses in algae other than blue-greens are probably not uncommon ;
whether they can be utilized for control purposes remains questionable. ;
Virus-like inclusions have been isolated from the green algae Stigeoclonium,

37


EPA-600/3-77-084
July 1977

BIOLOGICAL CONTROL OF AQUATIC NUISANCES - A REVIEW

by

Gerald S. Schuytema
Marine and Freshwater Ecology Branch
Corvallis Environmental Research Laboratory
Corvallis, Oregon 97330

CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330


152.

153.

154.

155.

156.

157.

158.

159.

160.

161.

162.

163.

164.

165.

166.

Decell, J. L. 1974. Water hyacinth work in Puerto Rico. U. S. Army
Waterways Experiment Station, Vicksburg, Miss. Notice of Research
Project, Smithsonian Science Information Exchange, Washington, D.
C. SIE No. 2TK-304,

Seaman, D. E. and W. A. Porterfield. 1962. Feasibility of controlling
aquatic weeds with snails. Proc. South. Weed Conf. 15:256-257.

Seaman, D. E. and W. A. Porterfield. 1964. Control of aquatic weeds by
the snail Marisa cornuarietis. Weeds 12:87-91.

Blackburn, R. D., T. M. Taylor, and D. L. Sutton. 1971. Temperature
tolerance and necessary stocking rates of Marisa cornuarietis L.
for aquatic weed control. Proc. Int. Symp. on Aquatic Weeds.
Oxford 3:79-86.

Ferguson, F. F. and J. M. Butler, Jr. 1966. Ecology of Marisa and its
potential as an agent for the elimination of aquatic weeds in
Puerto Rico. Proc. South. Weed Conf. 19:468-476.

Radke, M. G., L. S. Ritchie, and F. F. Ferguson. 1961. Demonstrated
control of Australorbis glabratus by Marisa cornuarietis under
field conditions in Puerto Rico. Amer. J. of Trop. Med. and Hyg.
10:370-373.

Blackburn, R. D. and L. W. Weldon. 1965. A fresh water snail as a weed
control agent. Proc. South. Weed Conf. 18:589. (Abstr.)

Blackburn, R. D. and T. M. Taylor. 1968. Snails for aquatic weed
control. Proc. Weed Sci. Soc. Amer. 8:51. (Abstr.)

forego Research. 1968. Biological control of aquatic weeds.
6(8) :8-9.

Rich, E. R. and W. Rouse. 1970. Mass producing a tropical snail for
biological control. Proc. South. Weed Conf. 23:288-298.

Hubendick B. 1966. Some aspects of vector snail control. Malacologia
5(1) 231-32.

Partington, W. M. 1968. Florida Audubon's viewpoint on aquatic weed
control. Hyacinth Control J. 7:21-23.

Partington, W. M. 1968. Aquatic plants and wildlife. Florida Natur.
41(4) 3141-143.

Chokder, A. H. 1968. Further investigations on control of aquatic
vegetation in fisheries. Agr. Pakistan 19(1): 101-118.

Abrahamsson, S. A. A. 1966. Dynamics of an isolated population of the
crayfish Astacus astacus Linn. Oikos 17:96-107.

60


SECTION 7
ECONOMICS OF BIOLOGICAL CONTROL

Little has been published on the cost of biological control practices.
However, they are often advocated as less costly than other methods because
of ease of initiation, minimum requirements for trained personnel, and gen-
eral longevity of treatment (37). These considerations are important in less
developed countries (165, 531).

That biological control offers an economic, as well as ecological,
alternative to herbicides was demonstrated by Bates (185) who compared the
costs between use of the amur and chemical treatment in Arkansas and Alabama
farm ponds. The annual cost per year for chemical control was estimated at
$141/ha, whereas the annual cost per hectare over a 10 year period for bio-
logical control was estimated at $25. Aquatic weed control costs were re-
duced from an annual expense of $3,000-5,000 to an initial cost of only $25
after the introduction of Java tilapia at a Hawaiian sugar company (Hee,
cited in 61). It was predicted that this tilapia could be produced for
slightly over $1/kg in 1960 (Shefler, cited in 297).

Virtually no economic information could be found on biological control
procedures using organisms other than fish. One study has indicated that the
snail Marsia cornuarietis could be reared for about six cents each if 12
million a year were produced; however, this cost makes the high stocking
rates necessary for control impractical in most waters (532). As biological
control procedures become utilized to a greater extent and the costs of
mechanical and chemical treatment continue to rise, practices considered too

costly now may become acceptable.

46


to predator pressure and lack of a rapid natural dispersal method; a greater
impact on alligator weed is expected as populations increase (103).

Mites--

The mite Orthogalumna terrebrantis is a promising candidate for the
control of the water hyacinth (147). Studies are continuing on this form
(88, 89, 137) which has both North and South American varieties (75, 145).
Recent studies have indicated little difference between these populations
(148). The adults do not penetrate unbroken water hyacinth epidermis, whereas
the immature stages can feed freely (147) and severely damage the plant by
~vidermal stripping (137). Serious damage to water hyacinth in Argentina has
occurred at population levels sufficient to form approximately 10,000 mite
feeding galleries per plant (148).

Snails.
Pomacea-~

The snail Pomacea australis, about 5 cm in diameter and weighing up to
27 g, is widely distributed in Brazil and has shown promise in controlling a
variety of floating and submerged weeds (14, 37, 149). Ninety-three snails,
weighing about 7 g each, reduced 5,000 g of water hyacinth to 260 g in 43
days, while 95 snails weighing about 2-4 g consumed 2,500 g of water lettuce
in 29 days (150). Rushing has urged an investigation of P. australis as a
biological control agent of water hyacinth (151). and feasibility studies are
in progress in Puerto Rico (152).

Marsia

sheds of South America was discovered in the United States in 1957. The
adults may reach a length of over 6 cm and are very hardy (96). It has
eliminated submerged weeds in ponds in the southern United States and Puerto
Rico (14) and has been reviewed as a candidate biological control agent
(150). M. cornuarietis consumes a variety of aquatic macrophytes, and also
iyo the growth of water hyacinth by root-pruning (149, 153, 154, 155,
156).

Ponds containing 1,814 - 4,536 kg of ornamental lilies (Nymphaea
ampla) and 473-7,570 m> of water were cleared of foliage in 5 ue weeks after

the introduction of 200 M. cornuarietis each (157). On a larger scale, some
small ponds and lakes in Florida stocked with the snails at the rate of
9,875-19,750/ha were free of submerged weeds in 12 to 18 months (96, 158,
159). A high stocking rate was considered necessary (156) and 80,000 adult
M. cornuarietis/ha (155) were recommended for dense macrophyte infestations
(155). The need for mass production of these snails was emphasized (160) .
and some mass rearing techniques have been developed (161). M. cornuarietis
is also an efficient predator upon various snails which are vectors for

schistosomiasis and liver flukes (162).

The snail cannot survive below 6 C; 10 C is the lowest temperature at
which it can be expected to operate as an effective control (14, 155). This
might preclude its use in the United States (4). Partington (163, 164)
cautioned that this snail must not compete with certain native species or

20


CONTROL OF MACROPHYTES
Insects and Mites

General --

Many insects used or proposed for macrophyte control in this country are
native tO South America where research on suitable candidates for introduc-
tion into the United States is still in progress (74). According to Coulson
(75), who reviewed the U.S. Army Corps of Engineers activity in this area,
field surveys are conducted 1) to locate natural enemies 2) to determine
their life history and effectiveness as controls, and 3) to determine feeding
specificity and:food preference for the most promising candidates. Further
tests in this country are usually conducted before release. The importation
and interstate movement’ of potential control insects is regulated primarily
by the Quarantine AgrfcuT tural Inspection Division of the U.S. Department of
Agriculture. Work is also in progress evaluating the control potential of
various insects in India (76). Some of the earlier surveys for insects and
mites in Trinidad and northern South America have been summarized by Bennett
(77, 78). Andres and Bennett (15) stressed that great attention is given to
host ang ty and the poténtial for damaging nontarget plants when con-
sidering insects for biological control. “De Loach (79) emphasized the fol-
lowing research needs pertaining to insects as biological controls: deter-
mine if the parasites, predators and pathogens of native insects will attack
the introduced species; determine if native plants will be attacked; document
both the extent of control and monetary savings; and with careful ecological
studies, determine if satisfactory control was obtained.

In the terrestrial environment, competition among forage plants, which
are encouraged to. grow, assists biological control agents in suppressing
weeds. This competition may be minimal in the aquatic environment where
relatively high concentrations of macrophytes may not be desired (15).
Organisms which are less host specific than comparable ones attacking ter-
restrial plants have been suggested for macrophyte control if they are re-
stricted to water and do not damage economically valuable plants (80).

Neochetina--

The weevil Neochetina, native-to Argentina, Bolivia and Trinidad (81,
82) is one of the most promising insects for the biological control of the
water hyacinth, (Eichhornia crassipes) (83). The biology, ecological rela-
tionships and identification of these weevils in South America has been under
recent study (84, 85, 86, 87) and two introduced species, N. bruchi and N.
eichhorniae, have become established at over 60 sites in Florida ‘da (Spencer,

cited in 88).

N. bruchi, which will consume small quantities of other plants of the
same taxonomic family (89), depends upon the water hyacinth to complete its
life cycle (5). De Loach (90) concluded that this species is sufficiently
host-specific to be safely introduced into the United States.



of the amur into the open waters of North America until it has been studied
in more detail (283, 284). The Soil Conservation Service has emphasized the
danger of introducing exotic species and has opposed the introduction of the
amur because it might interfere with rice culture and waterfowl management
(285, 286). Thirty-five states are now reported to have prohibited the
importation and release of the amur (287). The decision by only a few to
import amur into the United States in 1963 was emphasized as one which may
affect the country for decades or centuries to come (288).

Research needs--Much of the early work on the amur was based on short term
quasi-scientific, uncontrolled observations (289). The need for thorough
study was emphasized by Stevenson (231). Others have advocated the need to
develop good information on the effect of competition with native fish,
optimum stocking rates of different size fish, the probability of spreading
of new diseases, establishment of the amur in natural waters, effect upon
waterfowl habitat and other organisms, effect of egested and excreted ma-
terial and determination of control effectiveness of the weeds in question
(268, 272, 290).

Tilapia--

Tilapia are often used to control aquatic vegetation in artificial lakes
and ponds created primarily for aesthetic values (291), and attempts to
utilize these fish for aquatic vascular plant control throughout the warmer
regions of the world have had varying degrees of success.

Tilapia mossambica consumes some vascular plants incidental to its
grazing of attached algae; these include common duckweed (Lemna minor),
azolla (Azolla), cambomba (Cambomba carolinana), parrot feather, curly leaf
pond weed (Potamogeton crispus), vallisneria, and southern naiad. These fish
do not utilize water hyacinth but can eliminate it by destroying roots and
stems (35). Studies on its feeding and growth have been conducted in Alabama
(292). St. Amant and Stevens (293) prepared a bibliography of 213 selected
references on this tilapia.

T. melanopleura prefers macrophytes to algae after it develops beyond
the fry stage foeay. In Rhodesia, it consumes 64 percent higher plants

and 19 percent cladocerans and chironomids (34). JT. zillii in Egypt also
feeds upon both plant and animal material (295). Macrophyte density has
decreased with no apparent effect upon the native fish in some southern
California irrigation canals where T. zillii has been introduced (296, 297,
298). This species, in addition to T. melanopleura, is important in control
of soft vegetation in Kenya (299). T. melanopleura has also been reported as
a more efficient weed control agent than either the Java tilapia or the Nile
tilapia, T. nilotica (61). Reservoirs in Puerto Rico have been stocked with
tilapia in an attempt to control aquatic weeds (300).

The inability of tilapia to survive temperatures below 7.5-10 C in
California is believed to be an effective barrier to their distribution; they
would have to be restocked annually to become effective controls (297, 301).
Weed control may be ineffective unless tilapia are stocked in substantial

28


61.

62.

63.

64.

65.

66.

67.

68.

69.

70.

71.

72.

73.

74,

75.

Avault, J. W., R. O. Smitherman, and E. W. Shell. 1968. Evaluation of
eight species of fish for aquatic weed control. FAO Fish. Rep.
44(5):109-122.

Cook, S. F., Jr. 1968. The potential role of fishery management in the
reduction of chaoborid midge populations and water quality enhance-
ment. Calif. Vector Views. 15(7):63-70.

Cook, S. F., Jr. and R. L. Moore. 1970. Mississippi silversides,
Menidia audens (Atherinidae), established in California. Trans.
Amer. Fish. Soc. 99(1):70-73.

St. Amant, J. A. 1970. The Department of Fish and Game's role in
aquatic plant control. Proc. Calif. Weed Conf. 22:23-26.

Pruginin, Y., S. Shilo, and D. Mires. 1975. Grey mullet: A component
in polyculture in Israel. Aquaculture 5:291-298.

Tang, Y. and T. Hwang. 1966. Evaluation of the relative suitability of
various groups of algae as food of the milkfish in brackish-water
ponds. FAO Fish. Rep. 44(3): 365-372.

Ling, S. W. 1966. Feeds and feeding of warm-water fishes in Asia and
the Far East. FAO Fish. Rep. 44(3):291-309.

Hickling, C. F. 1961. Tropical inland fisheries. Longmans Green,
London. 281 p.

Tang, Y. and S. Chen. 1966. A survey of the algal pasture soils of
milkfish ponds in Taiwan. FAO Fish. Rep. 44(3):198-209.

Carbine, W. F. 1948. Bangos culture in the Philippines. Prog. Fish
Cult. 10:187-197.

Food and Agriculture Organization of the United Nations. 1969. Weed
control. FAQ Aquacult. Bull. 2(1):6.

Van Deusen, R. D. 1974. Swans-benefical and beautiful. Prog. Farmer.
September. p. 82.

National Science Research Concil of Guyana. 1973. Some prospects for
aquatic weed management in Guyana. Proc. Workshop on Aquatic Weed
Management and Utilization. 53 p. (NTIS PB-228 660)

De Loach, C. J. 1975. Aquatic weeds and their control. Biological
control of Weed Lab, Hurlingham, Argentina. Notice of Research
Project, Smithsonian Science Information Exchange, Washington, D.
C. SIE No. GY-41269.

Coulson, J. R. 1971 Prognosis for control of water hyacinth by ar-
thropods. Hyacinth Control J. 9(1):31-34.

52


283.

284,
285.

286.

287.

288.

289.
290.

291.

292.

293.

294.

295.

296.

297.

Sport Fishing Institute. 1969. Conference on exotic fishes and related
problems. SFI Bull. 203:1-4.

Sport Fishing Institute. 1969. Grass carp doubts. SFI Bull. 205:2.

Sport Fishing Institute. 1973. Exotic species policy. SFI Bull.
241:7.

Food and Agriculture Organization of the United Nations. 1973. Grass
carp in the United States. FAO Aquaculture Bull. 5(3-4):19.

Sport Fishing Institute. 1977. Grass carp outlawed in 35 states.
SFI Bull. 282:5.

Sport Fishing Institute. 1972. White amur in Arkansas. SFI Bull.
239:4-5.

Sport Fishing Institute. 1972. Grass carp policy. SFI Bull. 236:3-4.

Blackburn, R. D. 1970. Research needs in the field of aquatic
weed control. p. 1-5. In Proc. aquatic plant res. conf. Governor's
Aquatic Res. and Development Comm. Gainesville, Feb. 20.

Childers, W. F., and G. W. Bennett. 1967. Experimental vegetation
control by large mouth bass-tilapia combinations. J. Wildlife
Manag. 31(3):401-407.

Shell, E. W. 1966. Relationship between rate of feeding, rate of
growth, and rate of conversion in feeding trials with two species
of tilapia Tilapia mossambica Peters and
Tilapia nilotica Linnaeus. FAO Fish. Rep. 44(3):411-415.

St. Amant, J. A. and M. C. Stevens. 1967. Bibliography of
publications concerning Tilapia mossambica (Peters) Resources
Agency of California. Inland Fisheries Admin. Rep. 67-3. 12 p.

Mann, H. 1966. The utilization of food by Tilapia melanopleura, Dum.
FAO Fish. Rep. 44(3):408-410.

Abdel-Malek, S. A. 1972. Food and feeding habits of some Egyptian
fishes in Lake Quarun: I. Tilapia zillii (Cerv.) C. According to
different sexes. Bull. Inst. Oceanogr. Fish. 2:239-259 (WRSIC
Abstr. W75-00350).

Hauser, W. J. and E. F. Legner. 1974. Biological control of aquatic
weeds in the lower Colorado River Basin. Annual Report. Univ. of
Calif. Riverside. 31 p.

Hauser, W. 1975. Can Tilapia replace herbicides? In Proc. 6th Annual
California-Nevada Amer. Fish Soc. Meeting. Sacramento. 13 p.

70


Fish
Amur --

General--The potential success of the white amur or grass carp (Cteno-.
pharyngodon idella) for biological control of aquatic weeds has often been
emphasized (174, 175, 176, 177). Nair (178) compiled a bibliography of 243
references from 1934 to 1968 on its culture and application. Reviews and
evaluations of its biological control potential have been presented by Cagni,
Sutton and Blackburn (179), Bailey (180), Michewicz, Sutton and Blackburn
(175) and Greenfield (181). Major research programs on the amur in the
United States have been conducted in Alabama by Auburn University, in Florida
by the U.S. Department of Agriculture and the University of Florida, and in
(iss by the U.S. Department of Interior and the University of Georgia

182).

The range of the amur extends from 23° to 50° N (183); it is native to
rivers entering the western Pacific from China, and has been introduced into
the United States, Malaysia, Formosa, India, Japan, western Europe, eastern
Europe and the U.S.S.R. (184). The fish is now reported in 44 of 50 states
in the U.S.A. (Kennamer, cited in 185).

To spawn in its native China, the amur needs a sudden rise in water
level (exceeding 1.2 m in 12 hours), a flow of approximately 60-100 m/min,
and a water temperature of 26-30 C (186). Little water movement is needed
for the successful hatching of eggs provided they remain suspended for 40
minutes after fertilization (183)

The growth rate of the amur is exceeded by few other fish (187) and
ranges from 2.8 g/day in northern latitudes to 8-10 g/day in the equatorial
regions (188). Maximum size exceeds 30 kg and 1.0 m in length (189).

The upper lethal temperature is approximately 37-39 C and overwintering
can occur at 1-2 C (189). Low oxygen tensions can be tolerated (190) but
feeding ceases at 2.5 mg/l, decreasing their value as a control at lower
oxygen levels (191).

The amur is a popular food fish in Japan (192) and it is considered
among the most important fish cultivated in Asia (193). It is also grown for
food in eastern Europe (50, 194) and the U.S.S.R. (56). While its food value
is often a secondary benefit in weed control projects (195, 196) considera-
tion should be given the possibility of eating fish which have ingested weeds
containing toxic substances such as arsenic (197).

Stocking the amur has changed the natural habitat in some Arkansas lakes
resulting in replacement of the redear sunfish (Lepomis microlophus) and
chain pickerel (Esox niger) by largemouth bass (Micropterus salmoides),
bluegill (Leopomis macrochirus) and the gizzard shad (Dorosoina cepedianum
(198). While the amur usually does not appear to compete with game fish for
food (199), its ability to consume common invertebrates has been demonstrated
(200). There were no significant changes in the phytoplankton after amur

22


516.

517.

518.

519,

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621.

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524.

525.

526.

527.

528.

Pratt, R., J. F. Oneto, and J. Pratt. 1945. Studies on Chlorella
vulgaris. X. Influence of the age of the culture on the accumula-
tion of chlorellin. Amer. J. Bot. 32:405-408.

Pratt, R. 1942. Studies on Chlorella vulgaris. V. Some properties of
the growth-inhibitor formed by Chlorella cells. Amer. J. Bot.
29:142-148.

Pratt, R. 1943. Studies on Chlorella vulgaris. VI. Retardation of
photosynthesis by a growth-inhibiting substance from Chlorella
vulgaris. Amer. J. Bot. 30:32-33.

Fitzgerald, G. P. 1964. The biotic relationships within waterblooms.
p. 300-306. In D. F. Jackson (ed.) Algae and Man. Plenum Press,
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Fitzgerald, G. P. 1969.. Some factors in the competition or antagonism
among bacteria, algae, and aquatic weeds. J. Phycol. 5(4):351-
359.

Hasler, A. D. and E. Jones. 1949. Demonstration of the antagonistic
action of large aquatic plants on algae and rotifers. Ecology
30: 359-364.

Tassigny, M. and M. Lefevre. 1971. Autoantagonism, heteroantagonism
and other consequences of the excretions of algae from fresh or
thermal water. Verh. Int. Verein. Limnol. 19:26-38.

Boyd, C. E. 1973. Biotic interactions between different species of
algae. J. Weed Sci. Soc. Amer. 21(1):32-37.

Harris, D. 0. 1971. Inhibition of oxygen evolution in Volvox globator
by culture filtrates from Pandorina morum. Microbios  3(9):73-75.

Harris, D. 0. 1972. Life history and growth inhibition studies in
Platydorina candata (Volvocaceae). Res. Rep. Dep. Bot. Univ.
Kentucky, Lexington. (WRSIC Abstr. W73-13900).

Harris, D. 0. 1972. Further observations on a growth inhibiting
substances produced by Pandorina morum. Res. Rep. Dep. Bota.
Univ. Kentucky. (WRSIC Abstr. W73-13900).

Harris, D. 0. and M. C. Parekh. 1973. A study of water-soluble
inhibitory compounds (algicides) produced by fresh-water algae.
Kentucky Water Resources Institute, Lexington. 34 p.

(NTIS PB-229 831)

Harris, D. 0. and H. D. Caldwell. 1974. A study of naturally occurring

algicides produced by freshwater algae. Kentucky Water Resources
Inst., Lexington. 39 p. (NTIS PB-238 349/5GA)

88


SECTION 2
CONCLUSIONS

Biological control is becoming increasingly significant as a management
approach to alleviate symptoms of eutrophication. However, most research has
been at the laboratory pilot scale level or with relatively few well docu-
mented instances of large-scale control projects. While this type of control
deals only with the symptoms of excessive nutrient loading, it appears to be
the only feasible solution in many situations.

Biological control of aquatic nuisances in this country was initially
concerned with macrophyte control in the southeast, where drainage and
navigation were affected. More recent studies have been concerned with
controls of wider application. Macrophytes are most often the problem in the
southern United States, and algal blooms in the north. Obviously, no one
approach will be applicable to all locations. Selected procedures that have
been proposed or utilized are summarized in Table 1.

Grazing and predation have been the most frequently utilized techniques,
with most emphasis on macrophyte control by fish. Many grazers and predators
are not host-specific and represent potential hazards to desirable components
of the ecosystem. Therefore, their use must be carefully evaluated. Some
control organisms, such as insects, tend to be restricted to a particular
target species and thus may be more desirable as management tools; however,
climate often limits their effectiveness.

Pathogens are considered potentially effective control organisms, but
have not yet been used in full-scale control projects. Most pathogens are
host-specific, relieving the threat of damage to nontarget species. Most
promising work has been with macrophytes; algal control is under study but
has not yet been achieved outside the laboratory.

Biomanipulation, which takes advantage of biotic interactions within an
ecosystem, is considered by many the most promising biological management
technique for eutrophic systems. Increasing algae grazers through direct
innoculation or chemical stimulation, after controlling zooplanktivores with
pathogens or carnivorous fish introductions, exemplifies such an approach.
Exploiting competitive and growth-limiting reactions among various species,
and shifting algal populations from blue-greens to greens by chemical addi-
tion or circulation are also promising areas under study.


298.

299.

300.

301.

302.

303.

304.

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306.

307.
308.

309.

310.

311.

Hauser, W. J. 1975. Influence of diet on growth of juvenile Tilapia
Zillii. Prog. Fish. Cult. 37(1):33-35.

van der Lingen, M. I. 1968. Control of pond weeds. FAO Fisheries Rep.
44(5):53-60.

Gracia, W. H. 1966. The need of aquatic weed control in Puerto Rico.
Proc. South. Weed Conf. 19:454-455,

Hauser, W. 1975. Tilapia as biological control agents for aquatic
weeds and noxious aquatic insects in California. Univ. Calif.
Imperial Valley Field Sta. Manuscript. 11 p.

Crittenden, E. 1962. Status of Tilapia nilotica (Linnaeus) in Florida.
Proc. Southeast. Ass. Game and Fish Comm. 16:257-262.

Junor, F. J. R. 1969. Tilapia melanopleura Dum. in artificial lakes
and dams in Rhodesia with special reference to its undesirable
effects. Rhodesian J. Agr. Res. 7(1):61-69.

Kenmuir, D. H. S. 1973. Observations on a breeding pair of Tilapia
rendalli rendalli Boulenger 1968 in an experimental tank at Lake
Kariba Fisheries Research Institute. Hydrobiologia 43(3/4) :365-
370.

Wager, V. A. 1968. Destruction by tilapia. AFR Wildlife. 22(4):328-
339. (Biol. Abstr. 51:82216)

Courtenay, W. R., Jr., H. F. SahIman, W. W. Miley II, and D. J. Herrema.
1974. Exotic fishes in fresh and brackish waters of Florida.
Biol. Conservation. 6(4):292-302.

Nature. 1975. Aquatic biological pollution in Florida. 253(5489):238.

Reite, 0. B., G. M. 0. Malory, and B. Aasehaug. 1974. pH, salinity and
temperature tolerance of Lake Magadi Tilapia. Nature 247(5439):
315.

Bruton, M. N. and B. R. Allanson. 1974. The growth of Tilapia mossam-
bica Peters (Pisces: Cichlidae) in Lake Sibaya, South Africa. J.
Fish Biol. 6(6):701-715.

Cahn, A. R. 1929. The effect of carp on a small lake: The carp as a
dominant. Ecology 10:271-274.

Threinen, C. W. 1949. The effect of carp upon the normal aquatic

habitat. Wis. Conserv. Dept., Fish. Biol. Sect., Invest. Rep.
709. 21 p.

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385.

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387.

388.

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393.

Khudyakov, I. Y. and B. V. Gromov. 1973. The temperate cyanophage

A-4 (L) of the blue-green alga Anaba «ha 14 a a .
42:904-970. (Translation) 92 Anabaena variabilis. Mikrobiologiya

Venkataraman, G. S., B. D. Kaushik, G. Subramani
: S.5 B.D. > G@ jan, S. Shanmugasundaram,
and A. Govindarajan. 1973. Cyanophage AC-1:° a phage infecting

unicellular and colonial blue- i :
42:104-105. ue-green algae. Current Sci. (India)

Granhall, U. 1972. Aphanizomenon flos-aquae: infection by
cyanophages. Physiol. Plantarum 26: 332-337.

Singh, R, N. and P. K. Singh. 1967. Isolation of cyanophages from
India. Nature 216:1020-1021.

Safferman, R. S., T. 0. Diener, P. R. Desjardins, and M. E. Morris.
1972. Isolation and characterization of AS-1, a phycovirus infect-
ing the blue-green algae, Anacystis nidulans and Synechococcus
cedrorum. Virology 47:105-113.

Daft, M. J., J. Begg, and W. D. P. Stewart. 1970. A virus of blue-
green algae from freshwater habitats in Scotland. New Phytol.
69:1029-1038.

Padan, E., M. Shilo, and N. Kislev. 1967. Isolation of "cyanophages"
from freshwater ponds and their interaction with Plectonema
boryanum. Virology 32:234-246.

Safferman, R. S., M. E. Morris, L. A. Sherman, and R. Haselkorn. 1969.
Serological and electron microcsopic characterization of a new
group of blue-green algal viruses (LPP-2). Virology 39:775-780.

Padan, E., A. Rimon, D. Ginzburg, and M. Shilo. 1971. A thermosensi-
tive cyanophage (LLP-1G) attacking the blue-green alga Plectonema
boryanum. Virology 45:773-776.

Adolph, K. W. and R. Haselkorn. 1971. Isolation and characterization
of a virus infecting the blue-green alga Nostoc muscorum. Virology

46: 200-208.

Adolph, K. W. and R. Haselkorn. 1973. Blue-green algal virus N-1:
physical properties and disassembly into structural parts. Viro-

logy 53:427-440.

Jansen, G. P. and D. L. Parker. 1975, Isolation, purification and
partal characterization of a virus infecting certain blue-green
algae. Am. Soc. Microbiol. National meeting. New York, N. Y.

Apr. 27-May 2. (Abstr.)
Safferman, R. S., I. R. Schneider, R. L. Steere, M. E. Morris, and T. 0.

Diener. 1969. Phycovirus SM-1: a virus infecting unicellular
blue-green algae. Virology 37:386-395.

77


Foreword

Preface

Abstract
1.
2.

CONTENTS

ER iii
ES iv
ES vi
Introduction ... cies eee c cece cece cece ee eee cence eee sence ees 1
CONCTUSIONS Locke e cee cece cece cence eee tence eee e een en tees 3
Recommendations .....cciecceec erence crete tenet eee enaeeneens 10
Grazing and Predation .. cc cece cseee cece e eee eee e eect eeeteees 12
Control Of Algae Lee eee cece cece reece cette eens 12
PrOCOZOANS Levee cece cece eee teen teen tenet eeenene 12
ZOOPTANKtON Lecce cece ee ec eee cece eee e ete eee 12

FISH occ cece c cee eee erent eee eee t ete n eens 13

BiVdS Loc cece cece e eect terete eee e een eee eee 15

Control of MacrophyteS ..... cc cece cece cere eee e eee e eee 16
Insects and MiteS ...cce cece cece eee cence ee eeneeee 16

ASS 20

CLAYFISN Loc cece cece eee eee e eee nent eeeenateee 21

TUPEIES cece cece cece renee eet eee t ete enennene 21

FISN coc ccc eee e eter eee e een nett eee e ee beeen 22

0) 30

MaMMAlS .. cece cee cece rete ete eee ete n ee teeeees 3]

vii


354.

355.

356.

357.

358.

359.

360.

361.

362.

363.

364.

365.

366.

367.

Bay, E. C. and L. D. Anderson. 1965. Chironomid control by carp and
goldfish. Mosquito News 25(3):310-316.

Hilsenhoff, W. 1962. Predation of Tendipes plumosus larvae by the

leech, Helobdella stagnalis. 10th Ann. Meeting, Midwest Bentholog-
(ieee ey St. Mary's College, Winona, Minnesota. April 26-27.
str.

Moyle, P. B., L. W. Fisher, and H. W. Li. 1974. Mississippi silversides
and logperch in the Sacramento-San Joaquin River system. Calif.
Fish and Game 60(3):144-149.

National Academy of Sciences. 1970. Principles of plant and animal
pest control, Vol. 5. Vertebrate Pests: Problems and Control.
153 p.

Northcote, T. G. 1970. Advances in management of fish in natural lakes
of western North America. p. 129-139. In A century of fisheries
in North America. Amer. Fish. Soc. Spec. Publ. 7.

Beard, T. D. 1971. Panfish literature review. Wisconsin Department of
Natural Resources. Res. Rep. 71. 44 p.

Graham, L. K. 1971. A review of the literature on bluegills in ponds.
Missouri Department of Conservation. No. F-1-R-20/Study no. I-
13/Job I. 30 p.

von Geldern, C. E., Jr. 1966. Warmwater lake management. p. 304-312.
In Inland Fish. Manag. Calif. Dept. of Fish and Game.

Sport Fishing Institute. 1962. Predator stocking ineffective. SFI
Bull. 127:6-7.

Threinen, C. W. 1960. Results of walleye fingerling stocking in lakes
with stunted panfish. Summary Rep. Wis. Conserv. Dept. Madison.
4p.

Sport Fishing Institute. 1961. More on walleye stocking. SFI Bull.
117:2-3.

Scott, T. M., Jr. 1967. Spotted gar predation on bluegil1 and selected
forage species. Proc. Southeast. Ass. Game and Fish Comm. 21:357-
360.

Clark, C. F. 1964. Bluegill control experiment in Hamler Lake, Ohio.
Ohio Dep. Natur. Resources, Publ. W-335:4 5 p..

Pelton, J. Z. 1948. Three years of liberalized fishing at Lake Alma,
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75


489.
490.

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497.

498.

499,

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501.

502.

Hickling, C. F. 1966. Fish-hybridization. FAO Fish. Rep. 44(4):1-11.

Frank, P. A. and R. R. Yeo. 1975. Control of weeds and certain other
aquatic pests in the Pacific Southwest. Univ. of Calif. U.S.D.A.
Agric. Reg. Service, Davis, California. Notice of Research Pro-
ject, Smithsonian Science Information Exchange, Washington, D. C.
SIE No. GY-15828-6.

Bayless, J. D. 1967. Striped bass hatching and hybridization experi-
ments. Proc. Conf. Southeast. Assoc. Game and Fish Comm. 21:233-
244,

Bishop, R. D. 1967, Evaluation of the striped bass (Roccus chrysops)
hybrids and white bass (R. chrysops) hybrids after two years.
Proc. Conf. Southeast. Game and Fish Comm. 21:245-254.

Smith, E. V. and H. S. Swingle. 1941. The use of fertilization for
controlling pond-weed Najas guadalupensis. Trans. N. Amer. Wild?.
Conf. 6:245-251.

Smith, E. V. and H. S. Swingle. 1941. Control of spatterdock. (Nuphar
advena Ait.) in ponds. Trans. Amer. Fish. Soc. 70:363-368.

Swingle, H. S. 1947. Experiments on pond fertilization. Ala. Exper.
Sta. Bull. 264. 34 p.

Swingle, H. S. and E. V. Smith. 1942. Management of farm fish ponds.
Alabama Polytech. Inst. Agr. Expt. Sta. Bull. 254:1-23.

McNabb, C. D. 1974. An evaluation of widely used herbicides on aquatic
plants, fish and fishfood organisms. Mich. State Univ., Agr. Exp.
Sta., East Lansing. Notice of Research Project, Smithsonian Sci-
ence Information Exchange, Washington, D. C. SIE No. GY-12668-5.

Swingle, H. S., B. C. Gooch, and H. R. Rabanal. 1963. Phosphate
fertilization of ponds. Proc. Southeast. Ass. Game and Fish Comm.
17:213-218.

Walker, C. R. 1959. Control of certain aquatic weeds in Missouri farm
ponds. Weeds 7:310-316.

Davison, V. E., J. M. Lawrence, and L. V. Compton. 1962. Waterweed
control on farms and ranches. U. S. Dept. Agr. Farmer's Bull.
2181. 21 p.

Surber, E. W. 1948. Fertilization of a recreational lake to control
submerged plants. Prog. Fish. Cult. 10:53-58,.

Surber, E. W. 1949. Control of aquatic plants in ponds and lakes. U.
S. Dept. Int. Fish and Wildlife Ser. Fish. Leaflet 344. 20 p.

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DeLoach, C. J. 1975. Identification and biological notes on the spe-
cies of Neochetina that attack Pontederiaceae in Argentina (Col-
eoptera: Curculionidae: Bagoini). Coleopterists Bull. 29(4):
257-266.

DeLoach, C. J. and H. A. Cordo. 1976. Ecological studies of
Neochetina bruchi and N. eichhorniae on water hyacinth in Argentina.
J. Aquatic Plant Manage. 14:53-59.

Center, T. C. 1975. The use of insects for the biological control of
waterhyacinth in the United States. p. 51-59. In Brezonik, P. L.
and J. L. Fox (eds.) Proc. Symp. on water quality management
through biological control. Univ. of Florida and U. S. Environ-
mental Protection Agency, Gainesville, Jan. 29-31.

Spencer, N. R., D. D. Perkins, F. D. Bennett, and E. 0. Gangstad. 1974.
Insect Enemies of aquatic weeds. p. D 3-D 21. In Gangstad, E. 0.,
J. J. Raynes, C. R. Zeiger, J. M. Ingersoll, R. D. Gordon, et al.
Biological control of water hyacinth with insect enemies. Aquatic
Plant Control Program, Tech. Rep. 6. Army Eng. Waterways Exp. Sta.,
Vicksburg, Miss. (NTIS AD-775 408/8)

DeLoach, C. J. 1976. Neochetina bruchi, a biological control agent of
water hyacinth: Host specificity in Argentina. Ann. Entomol. Soc.
Amer. 69(4):635-642.

Perkins, B. D. 1974. Biological control of water hyacinth. U. S. Dep.
Agr. Agricultural Research Center, Fort Lauderdale, Florida.
Notice of Research Project, Smithsonian Science Information Ex-
change, Washington, D. C. SIE No. GY-22553-1.

Hudson, J. C. 1974. Aquatic plant research and control in Florida. p.
25-27. In Proc. research planning conference on integrated systems
of aquatic plant control. Army Eng. Waterways Exp. Sta., Vicks-
burg, Miss. (NTIS AD-787 302)

dames, B. L. 1975. Preliminary research at Agriculture Research Center,
Ft. Lauderdale, Fla. Agric. Res. Center, Fort Lauderdale. Notice
of Research Project, Smithsonian Science Information Exchange,
Washington, D. C. SIE No. GY-30332-5.

Guerra, L. V. 1975. Control programs for hyacinth and other aquatic
weeds. p. 60. In Brezonik, P. L. and J. L. Fox (eds.) Proc. symp.
on water quality management through biological control. Univ. of
Florida and U. S. Environmental Protection Agency. Gainesville,
dan, 29-31.

Blackburn, R. D. and W. C. Durden, Jr. 1975. Integrated control of
alligator weed. p. A3-A48. In Gangstad, E. 0., R. D. Blackburn,
W. C. Durden, Jr., T. C. Center, J. Balcuinas, A. Inglis, E. C.
Davis, D. E. Seaman, and J. H. Steenis. Integrated program for

54


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37.

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Prowse, G. A. 1969. The role of cultured pond fish in the control of
eutrophication in lakes and dams. Verh. Int. Verein. Limnol.
17:714-718.

Butler, J. M., Jr., F. Ferguson, and L. A. Berrios-Duran. 1968. Sig-
nificance of animal control of aquatic weeds. Proc. South. Weed
Conf. 21:304-308.

Shell, E. W. 1962. Herbivorous fish to control Pithophora and other
aquatic weeds in ponds. Weeds 10(4):326-327.

Lawrence, J. M. 1968. Aquatic weed control in fish ponds. FAO Fish.
Rep. 44(5):76-91.

Avault, J. W., Jr. 1965. Biological weed control with herbivorous
fish. Proc. South. Weed Conf. 18:590-591.

Pierce, P. C. and H. M. Yawn. 1965. Six field tests using two species
of tilapia for controlling aquatic vegetation. Proc. South. Weed
Conf. 18:582-583.

Pollard, J. R., R. L. Carpenter, J. P. Henderson, and H. G. Chichester.
1974. Horseshoe Lake thermal water research and demonstration
project. Study I - Raceway culture evaluation. Oklahoma Gas and
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Moriarty, D. J. W. 1973. The physiology of digestion of blue-
green algae in the cichlid fish, Tilapia nilotica. J. Zool., Lond.
171:25-39,

Moriarty, D. J. W. and C. M. Moriarty. 1973. The assimilation of
carbon from phytoplankton by two herbivorous fishes; Tilapia
nilotica and Haplochromis nigripinnus. J. Zool., Lond. 171: 41-
55.

Moriarty, C. M. and D. J. W. Moriarty. 1973. Quantitative estimation
of the daily ingestion of phytoplankton by Tilapia nilotica and
Haplochtomis nigripinnis in Lake George, Uganda. J. Zool., Lond.
171:15-23.

Ware, F. J., R. D. Gasaway, R. A. Martz, and T. F. Drda. 1975. In-
vestigations of herbivorous fishes in Florida. p. 79-84. In
Brezonik, P. L. and J. L. Fox (eds.) Proc. symp. on water quality
management through biological control. Univ. of Florida and U. S.
Environmental Protection Agency, Gainesville, Jan. 29-31.

Konradt, A. G. 1966. Methods of breeding the grass carp, Ctenopharyn-
godon idella and the silver carp, Hypopthalmichthys molitrix. FAO
Fish. Rep. 44(4):195-204.

50


SECTION 4
GRAZING AND PREDATION

Grazing by introduced organisms has often been suggested or used to
control aquatic nuisances. For example, certain protozoans, zooplankton and
fish consume algae while various insects, mites, snails, crayfish, turtles,
fish, fowl and mammals consume macrophytes. The predation of fish upon
undesirable insects and other fish has also been proposed or attempted as a

control mechanism.
CONTROL OF ALGAE

Protozoans

Protozoans can graze upon or parasitize members of all major planktonic
algal groups and a protozoan infestation is often followed by a decrease or
elimination of certain algae (18). Amoebae differ in their ability to utilize
algae. For instance, species of Chlamydomonas, Pandorina, Anabaena, Ankistro-
desmus and Gloeocystis were consumed in varying degrees by four test amoebae
(Amoeba discoides, A. radiosa, Hartmannella castellani, Tetramitus rostratus);
however, they would not eat Staurastrum or Chlorella (19). A large amoeba
associated with blooms of the blue-green alga Anabaena planctonica was sug-
gested as a possible treatment for certain nuisance algae (20). Ahearn (21
observed this amoeba to control a nuisance algal bloom in 2 or 3 days and
hoped to rear it in the laboratory so blooms could be seeded.

Ochromonas dancia, a chrysomonad alga, can feed upon the toxic blue-
green Microcystis aeruginosa (22). The effectiveness of using 0. dancia as a
control organism depends upon a number of factors requiring further investiga-
tion. These are a continuing rapid rate of intracellular digestion of M.
aeruginosa, maintenance of a high 0. dancia concentration, the selective
action of 0. dancia and the detoxification of M. aeruginosa during digestion

(23,24).

Zooplankton

Zooplankton stocking into reservoirs and other nutrient rich waters has
been suggested as a control for undesirable algae (25, 26). While increasing
zooplankton abundance may decrease phytoplankton populations, this technique
is of little benefit where inedible algal species are present (27). This was
the case in Clear Lake, California, where grazing zooplankton played a
negligible part in planktonic blue-green algae removal, apparently because

12


SECTION 6
BIOMANIPULATION

Considerable emphasis on biological control in the aquatic environment
has been on the use of predators, grazers, or pathogens to contro) undesir-
able species. Little effort has been directed toward exploiting the interre-
Jationships among the plants and animals and their environment to alleviate
symptoms of excessive production. Patten (472) emphasized that small or
inexpensive, well chosen, and correctly timed manipulations of ecosystem
parameters might produce dramatic improvements in water quality. Similarly,
Shapiro et al. (27) stressed the need to treat lakes as ecosystems rather
than focusing entirely on controlling nutrient input.

GRAZING

Zooplankton

Phytoplankton density often depends upon nutrient concentration and
zooplankton grazing. The latter in turn often depend upon phytoplankton
density. These relationships were studied by O'Brien and DeNoyelles (473)
who emphasized that such a system can only exist where zooplankton are not
rigorously limited by predation. Manipulation of these relationships thus
affords the possibility of lowering phytoplankton abundance to more desirable
levels by increasing the abundance of zooplankton.

Shapiro et al. (27) suggested that the deliberate stocking of large
herbivorous zooplankters such as Daphnia magna could control larger colonial
algae after reduction of zooplanktivores by carnivores. This technique was
felt to be of little benefit, however, where inedible phytoplankton species
were present. Algae populations in such cases might then be manipulated by
other means to favor production of those preferred by grazing zooplankton.
They also proposed investigation of pantothenic acid additions to lakes to
increase zooplankton populations but felt the economics of the treatment
would probably be prohibitive.

Other applicable research in progress on grazing concerns its importance
as an algal controlling factor in prairie lakes (474), and a mathematical
simulation model to explore ways to reduce algal standing crops by diverting
primary productivity into consumer food chains (475).

Tadpoles

Tadpoles can be a major factor in the spring reduction in the standing

4]


explained the shifts on the basis of competition for CO, or phosphate but
also suggested that the blue-greens may have been stresSed by these addi-
tions, thereby becoming more susceptible to cyanophages.

The importance of water circulation in algal population shifts was also
emphasized by Shapiro et al. (27). The hypothesis that it can cause a shift
by lowering the pH or increasing the CO. is being investigated (485). High
pH is also lethal to some zooplankton; Towering it by increasing circulation
was suggested as a possible method to increase the abundance of these gra-
zers with a subsequent lowering of the algal populations (27).

45


341.

342.

343,

344,

345.

346.
347.

348.

349.

350.

351.

352.

353.

Anthony, D. W. 1975. (Discussion) p. 152. In Bourquin, A. W., D. G.
Ahearn, and S. P. Meyers (eds.) Impact of the use of microorgan-
isms on the aquatic environment. U. S. Environmental Protection
Agency, Ecological Research Series 660/3-75-001.

BioScience. 1975. Workshop calls for manatee research center. 25(6):

Kleinschmidt, H. —E. 1974. Water hyacinth control. Queensland Agr. J.
(Australia) 100(6):229-230.

Davies, H. R. J. 1959. Effects of the water hyacinth (Eichhornia
crassipes) in the Nile Valley. Nature 184:1085-1086.

Linn, J. D. 1970. Fish and wildlife aspects of aquatic weed
control. Proc. West. Soc. Weed Sci. 23:67-69.

Engineering News Record. 1975. Florida weed eater. 194(19):16.

Soap and Detergent Association. 1976. Water in the News. Winter.
Newsletter.

Lapham, V. T. 1966. Aquatic weed control in Louisiana. Louisiana
Conserv. 18(11/12):12-23.

Bay, E. C. 1967. Potential for naturalistic control of mosquitoes
Proc. Ann. Conf. Calif. Mosquito Contr. Ass. 35:34-37.

Rees, D. M., D. M. Brown, and R. N. Winget. 1969. Mosquito larvae
control with Gambusia and Lucania fish in relation to water depth
and vegetation. Proc. Ann. Conf. Calif. Mosquito Contr. Ass.
37:110-114.

Aliyev, D. S. and R. Y. Bessmertnaya. 1968. The use of grass carp
(Ctenopharyngodon idella Val.) to control the larvae of blood-
sucking mosquitoes. Probl. of Ichthyol. Amer. Fish Soc. 8(2):
319-321.

Legner, E. F., M. S. Mulla, and T. W. Fisher. 1973. Natural enemies of
noxious nematocerous aquatic diptera. Univ. of Calif. Agricultural
Experiment Station, Riverside. Notice of Research Project, Smith-
sonian Science Information Exchange, Washington, D. C. SIE No. GY-
11597-4,

Legner, E. F., and R. A. Medved. 1973. Influence of Tilapia mossambica
(Peters), T. zillii (Gervais) (Cichlidae) and Mollienesia latipinna
Le Suer (Poeciliidae) on pond populations of Culex mosquitoes and
chironomid midges. Mosquito News 33(3):354-364.

74


TABLE 1 (continued)

Problem or Project Solution or Proposed Treatment Location Results or Remarks References
White amur (Ctenopharyngodon U.S.S.R. Amur at 79 kg/ha cleared 0.42 ha 235
idella) pond, with a July production of
16.2 metric tons/ha, in 70 days
Weeds in irrigation Tilapia zilli California Weed density appears less 297, 307
canals
Macrophytes in Tilapia nilotica Alabama Controlled macrophytes at 38, 40, 61
experimental Tilapia melanopleura stocking rates of 2,470-
Ponds 6,765/ha
Weed contro] Tilapia Rhodesia May have had detrimental van der
effect upon biota other than Lingen cited in
plants W
Tilapia Sudan Disappointing results 196
Rooted aquatics Israeli Carp Arkansas Controlled when stocked at 60, 319
123 0.23 kg fish/ha
Duckweeds and leafy Swan Michigan One pair per 0.2-0.4 ha pond 72, 325, 326
aquatics in ponds controls weeds
Muscovy ducks (Cairina moschata) Georgia, 15-20 ducks/ha eliminated 58, 322
Louisiana duckweeds
Choking of lakes Nutria (Myocaster coypu) Poland Reversed development of bog 328, 329, 330
by coarse emergent Jake, depleted vegetation
vegetation increased fish production
Water hyacinth Cattle grazing in canal Guyana Prevented spreading of mat 73
Manatee (Trichechus manatus) Guyana Sucessfully cleared and kept 72, 330, 336
clear various canals and ponds
for up to 15 years
B. PATHOGENS
Water hyacinth Virus stunt disease South U.S.A. May have control potential 426
Fungus-Rhizoctonia solani Florida Under study 378, 455

(continued)


23.

24.

25.

26.

27.

28.

29.

30

31.

32.

33.

34.

35.

Prows, B. L. and W. F. McIlhenny. 1973. Development of a selective
algaecide to control nuisance algal growth. U. S. Environmental
Protection Agency. Ecol. Res. Ser. EPA-660/3-73-006.

Cole, G. T. and M. J. Wynne. 1975. Possible utilization of the endo-
cytotic golden alga of Ochromanas dancia as a means of biological
control of nuisance blue-green algae. p. 118-119. In Brezonik, P.
L. and J. L. Fox (eds.) Proc. symp. on water quality management
through biological control. University of Florida and U. S. En-
vironmental Protection Agency, Gainesville, Jan. 29-31.

Bishop, J. W. 1969. Effects of zooplankton on photosynthesis by algae
in lakes. Virginia Polytechnic Inst., Water Resources Res. Center.
Bull. 31:89-93.

Steel, J. A. 1972. The application of fundamental limnological re-
search in water supply system design and management. Symp. Zoo.
Soc. London. 29:41-67.

Shapiro, J., V. Lamarra, and M. Lynch. 1975. Biomanipulation: An
ecosystem approach to lake restoration. p. 85-96. In Brezonik, P.
L. and J. L. Fox (eds.) Proc. symp. on water quality management
through biological control. Univ. of Florida and U. S. Environ-
mental Protection Agency, Gainesville, Jan. 29-31.

Horne, A. J. 1975. The ecology of Clear Lake phytoplankton. Clear Lake
Algal Research Unit. Lakeport, Ca. 116 p.

Edmondson, W. T. 1967. Why study blue-green algae? p. 1-6. In
Symposium on environmental requirements of blue-green algae. U. S.
Dept. Interior, Federal Water Pollution Control Admin., Corvallis,
Oregon.

Moriarty, D. J. W., J. P. E. C. Darlington, I. G. Dunn, C. M.
Moriarty, and M. P. Tevlin. 1973. Feeding and grazing in
Lake George, Uganda. Proc. R. Soc. Lond. B. 184:299-319.

Holmstrand, L. L. 1971. The role of the rotifer, Lindia
euchromata Edm. in the ecology of Gloeotrichia blooms. Limresta 2:

24-27.

Davis, J. S. and W. F. Gworek. 1972. A rotifer parasitizing Vaucheria
in a Florida spring. J. Phycol. 8(suppl.):18. (Abstr.)

Hickling, C. F. 1960. The Malacca tilapia hybrids. J. Genet. 57(1) :1-
10.

Munro, J. L. 1967. The food of a community of East African freshwater
fishes. J. Zool. 151(3):389-415.

Lahser, C. W. 1967. Tilapia mossambica as a fish for aquatic weed
control. Prog. Fish Cult. 29:48-50.

49


PREFACE

A diverse and widely based literature exists on biological control for
the management of eutrophic aquatic ecosystems. Excessive nutrient input
usually results in objectionable symptoms of eutrophication such as exces-
sive macrophyte development, algal blooms, dominance of undesirable fish and
nuisance insect populations. Biological manipulation in which a balanced
aquatic ecosystem is maintained, may be one means of alleviating these
symptoms when nutrient loading cannot be controlled.

For example, biological control (biocontrol), often utilized in agri-
cultural and other problem areas of the terrestrial environment, has become
important in aquatic weed control as a more satisfactory alternative to
chemical and mechanical procedures. While biological control of macrophytes
historically has focused on drainage problems and the choking of navigable
waterways, it has recently received more attention as part of lake restora-
tion measures. Control techniques in aquatic ecosystems can be divided into
three general categories: grazing and predation, in which undesirable forms
are controlled through the feeding activities of an introduced organism; use
of pathogens, the control of undesirable plants or animals by viruses,
bacteria or fungi; and biomanipulation, in which the interrelationships among
the plants, animals and their environment are adjusted to obtain a desired
degree of control and ecological balance. The literature has been reviewed
with respect to these categories.

Over 1,000 references on biological control or related topics in the
aquatic environment were located, most appearing between 1960 and 1976. A
total of 532 were included in this review. English units of measurement were
converted and reported in metric units.

Primary data bases and sources of literature included the following:

Water Resources Scientific Information Center
WRSIC data base - searched October, 1974
Selected Water Resources Abstracts - November 1974
to August, 1975

National Technical Information Service
NTIS data base- searched December, 1974
Government Reports Announcements - January, 1975 to
August, 1975

Bibliography of Agriculture

CAIN data base - searched December, 1974
CAIN current awareness searches - March, 1975 to

iv


230,

231.

232.

233.

234.

235.

236.

237.

238.

239,

240.

24).

242,

Terrel, J. W., and T. T. Terrel. 1975. Macrophyte control and food
habits of the grass carp in Georgia ponds. Verh. Int. Verein.
Limnol. 19:2515-2520.

Stevenson, J. H. 1965. Observations on grass carp in Arkansas. Prog.
Fish Cult. 27:203-206.

Agricultural Research. 1972. Fish that weed the water. Agr. Res. p.

Charyev, R. and D. S. Aliev. 1966. Experiments on the utilization of
grass carp for the control of water weeds in carp rearing ponds. In
Cultivation of herbivorous fishes. p. 77-82. (Biol. Abstr. 48:
99753)

Lupacheva, L. I. 1968. Higher aquatic vegetation in ponds of Tsyrup-
insk spawning-breeding farm. (Weed Abstr. 19:38, No. 242)

Zolotova, Z. K. and L. U. Khromov. 1970. The weeding role of grass
carp. (Sport Fish. Abstr. 18(4):386, No. 16873)

Zolotova, Z. K. 1970. Biological weed control in irrigation canals
with the aid of grass carp. (Sport Fish. Abstr. 18(4):398, No.
16923

Food and Agriculture Organization of the United Nations. 1969.
Weed Control. FAO Aquacult. Bull. 1(3):9.

Krupauer, V. 1970. Experience gained in the rearing of herbivorous
fish in Czechoslovakia. (Weed Abst. 19:174, No. 1151)

Ministry of Agriculture, Fisheries and Food, England and Wales. 1968.
The control of aquatic weed by grass carp. Res. Prog. Rep. 13-14.
(Weed Abstr. 18(6):432, 2701)

Stott, B. and T. 0. Robson. 1970. Efficiency of grass carp (Ctenophar-
yngodon idella Val.) in controlling submersed waterweeds. Nature
226:870.

Stott, B., D. G. Cross, R. E. Iszarol, and T. 0. Robson. 1971.
Recent work on grass carp in the United Kingdom from the standpoint
of its economics in controlling submerged aquatic plants. Proc.
Int. Symp. on Aquatic Weeds. Oxford. 3:105-116.

Sport Fishing Institute. 1972. Arkansas grass carp policy. SFI Bull.
37:2,

66


eliminate desirable vegetation.

Others--

Other instances involving snails have included experiments with the
Family Pilidae in East Pakistan (165), and the suggestion that Limnaea
stagnalis might control the submersed macrophyte Lagarosiphon in New Zealand

144). Rushing (150) recommended an exhaustive search for snails which would
be even more species specific than Pomacea and Marsia and emphasized that
snails are potentially important in an integrated aquatic plant control
program.

Crayfish

Reduced littoral vegetation is often associated with dense crayfish
populations (166, 167, 168). Dean (169) suggested control of aquatic vegeta-
tion by crayfish after Orconectes causeyi sucessfully cleared several lakes
in New Mexico of species of pondweed (Potomogeton), coontail, elodea (Elodea),
water buttercup (Ranunculus) and watermilfoil (169). Smartweed (Polygonum),
bulrush (Scirpus) and cattails (Typha) were not controlled. He emphasized
that crayfish desired for control purposes should be primarily vegetarian,
small to moderate in size, prolific and nonburrowing.

Q. causeyi was introduced into a 13 ha reservoir in South Dakota;
reproduction occurred but vegetation control was not documented (170).
Pacifasticus leniusculus was imported from Oregon to help clear vegetation
choked irrigation return ditches in Washington. Results were inconclusive
because of human predation and escapement, but research may continue (171;
Hesser, pers. comm.)

Magnuson et al., (172) indicated that while crayfish control nuisance
plants in some situations, they also prey upon fish eggs, reduce benthic
macroinvertebrates important as fish food, provide only a marginal food for
higher trophic level organisms and can eliminate native crayfish. They also
emphasized that once introduced, crayfish can be eliminated only with con-
siderable effort. Rickett (168) warned of the possibility of excessive
vegetation elimination in lakes or ponds by uncontrolled crayfish populations.

Turtles

Yount and Crossman's (173) studies suggest the possibility of training
turtles to eat water hyacinth. The Florida turtle, Pseudemys floridana
peninsularis normally eats only unhealthy hyacinths; however, turtles which
were preconditioned by eating crushed plants would eventually consume healthy
plants. Two of these animals consumed 23 kg of crushed and uncrushed water

hyacinths in 6 days.
Turtles have been used in aquatic weed control experiments in East
Pakistan (165), and the National Science Research Council of Guyana (73)

suggested that an economic incentive for cultivating certain South American
turtles for weed control might effect their declassification as endangered

species.

21


205.

206.

207.

208.

209.

210.

211.

212.

213.

214,

215.

216.

217.

Edwards, D. J. 1974. Weed preference and growth of young grass carp in
New Zealand. N. Z. J. of Marine and Freshwater Res. 8(2):341-350.

Fischer, Z. 1968. Food selection in grass carp (Ctenopharyngodon
idella Val.) under experimental conditions. Pol. Arch. Hydrobiol.

15(28):1-8.

Bhatia, H. L., C. A. Sastry, and R. K. Nigam. 1973. Control of
aquatic weeds from water bodies using grass carp. Indian J. of
Environ. Health. 15(2):92-99 (Eutrophication Abstr. 5890).

Krupauer, V. 1968. The plant consumption capacity of 3 and 4-year-old
grass carp. (Weed Abstr. 19:244, No. 1609)

Food and Agriculture Organization of the United Nations. 1969. Weed
control in ponds. FAO Aquacult. Bull. 1(2):6-7.

Prikhod'ko, V. A. and L. I. Lupacheva. 1967. The diet of grass carp.
(Weed Abstr. 18(6):433, No. 2704)

Avault, J. W., Jr. 1965. Preliminary studies with grass carp for
aquatic weed control. Prog. Fish Cult. 27:207-209.

Sutton, D. G. 1973. Control of aquatic plant growth in earthen ponds
by the white amur. App D. p. 41-55. In Gangstad, E. 0., W. T.
Nailon, and C. Novosad. Environmental impacts and research review
of the aquatic plant control program, Texas, Louisiana, Florida and
related areas. Army Eng. District, Galveston, Texas.

Sutton, D.L. and R. D. Blackburn. 1973. Feasibility of the amur
(Ctenopharyngodon idella Val.) as a biocontrol of aquatic weeds.
p. D3-D42. In —. 0. Gangstad, J. J. Raynes and R. M. Burress, et
al. Herbivorous fish for aquatic plant control. Aquatic Plant
Control Program, Tech. Rep 4, U. S. Army Eng. Waterways Exp. Sta.,
Vicksburg, Miss. (NTIS AD-765 437)

duntunen, E. T. and C. E. Bond. 1968. Progress Report. Research on
aquatic weed control. Oregon Agr. Exp. Sta. Project 773. p. 13-
14.

Singh, S. B., K. K. Sukumaran, K. K. Piliai, and P. C. Chakrabarti.
1967. Observations on efficacy of grass carp Ctenopharyngodon
idella (Val.) in controlling and utilizing aquatic weeds in ponds
in India. Proc. Indo-Pacific Fish. Council. 12:220-235.

Mehta, I. and R. K. Sharma. 1972. Control of aquatic weeds by the
white amur in Rajasthan, India. Hyacinth Control J. 10:16-19.

Beridze, I. 0. and R. I. Chkaidze. 1964. Some aspects of the

acclimatization of herbivorous fish in Georgia, U.S.S.R.
(Biol. Abstr. 48(19), No. 94337).

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Sutton, D. L. 1975. Control of aquatic plant growth. Agric. Res.
Center, Fort Lauderdale, Florida. Notice of Research Project.
Smithsonian Science Information Exchange, Washington, D. C. SIE
No. GY-61258-1.

Blackburn, R. D. and W. C. Durden. 1972, Integration of biological and
chemical control of alligatorweed. p. C3-C17. In Proc. Research
Planning Conf. on Aquatic Plant Control Project. Army Eng. Water-
ways Exp. Sta., Vicksburg, Miss. (NTIS AD-745 895)

Blackburn, R. D. and W. C. Durden. 1972. Integration of biological
and chemical control of alligatorweed. Agricultural Research
Center, Fort Lauderdale, Fl. 21 p. (NTIS AD-760 565)

Foret, J. A., N. R. Spencer, and E. 0. Gangstad. 1974. Towards in-
tegrated control of alligator weed. p. H3-H16. In Gangstad, E.
0., P. W. Zimmermann, A. E. Hitchcock, H. Kirkpatrick, T. T. Earle,
T. T. McClure, W. S. Stokes, F. S. Davis, D. P. Schultz, W. W.
Bruns, J. A. Foret, and N. R. Spencer. Aquatic-use patterns for 2,
4-D dimethylamine and integrated control. Aquatic Plant Control
Program. Tech. Rep. 7, Army Eng. Waterways Exp. Sta., Vicksburg,
Miss.

Benn, B. 0. and W. N. Rushing. 1975, Research on integrated control
of water hyacinth. U. S. Army Waterways Experiment Station,
Vicksburg, Miss. Notice of Research Project. Smithsonian Science
Information Exchange, Washington, D. C. SIE No. Z TK-654.

Sailer, R. I. 1971. Biological control of aquatic weeds--recent
progress. Proc. Northeast Weed Control Conf. 26:180-182.

Ghani, M. A. 1974. Orgainisms attacking Florida elodea in Pakistan.
Comm. Inst. of Biological Control. Rawalpindi, India. Notice of
Research Project, Smithsonian Science Information Exchange, Wash-
ington, D.C. SIE No. GY-21957-2.

Baloch, G. M., A. G. Khan, and M. A. Ghani. 1972. Phenology, biology
and host-specificity of some stenophagous insects attacking
Myriophyllum spp. in Pakistan. Hyacinth Control J. 10:13-16.

Smirnov, N. N. 1960. Nutrition of Galerucella nymphaeae L. (Chrysome-
lidae), mass consumer of water Tily. Hydrobiolgia 15(3):208-224.

DeLoach, C. J. A. D. DeLoach, and H. A. Cordo. 1976. Neohydronomus
pulchellus, a weevil attacking Pistia stratiotes in South America--

biology and host specificity. Entomol. Soc. Amer. 69(5):
830-834.

Spencer, N. R. and M. Lekic. 1974, Prospects for biological control of
Eurasian watermilfoil. Weed Sci. 22(4):401-404,

57


adaptability has made eradication unsuccessful (46).

Silver Carp-- . .
The silver carp (Hypothalmichthys molitrix) is a rapidly growing fish of
Chinese origin reaching 16 kg (47). The young change from a zooplankton to a
phytoplankton diet at about 18 days (48) when 1.5-3 cm long (49, 50). The
fish has been reported to avoid or to be unable to digest blue-green algae
and to prefer green algae and diatoms (36, 50). Others, however, have re-
ported assimilation of Aphanizomenon flos-aquae, Anabaena variabilis and

Anabaena spiroides (51, 52).

Silver carp need a temperature of at least 10 C, preferring 22-23 C
(50), but can withstand wintering in Polish carp ponds (49). Since it does
not spawn easily outside its native system (36), breeding is often induced by
hormone injections (47). The fish has reproduced successfully in the con-
fined waters of a reservoir in Taiwan (53).

This species has been introduced into the U.S.S.R., Poland, Rumania,
Bulgaria, Hungary, and Czechoslovakia for weed control and fish production
programs (50). It has been proposed as a means to control phytoplankton in
a Russian power station cooling reservior (54) and may become acclimated to
the southern regions of that country (55). It has also been introduced into
Lake Kinneret, Israel, to limit algal growth; however, results are inconclu-
sive (Serruya, cited in 17). It has reduced phytoplankton in an enclosure in
a Swedish lake (Carlsson, cited in 17). Introduction into a Singapore reser
voir to control algae is planned (Choon and Ling, cited in 17).

Thickhead--

The thickhead (Aristichthys nobilis), native to China, has been consi-
dered for phytoplankton control in Russian irrigation and drainage systems
and hydroelectric reservoirs (54, 56). This fish prefers planktonic diatoms
and green algae but will utilize blue-green algae, including Microcystis. It
has been introduced into the U.S.S.R., Rumania, Bulgaria, Hungary and Czech-
toot? where its main use has been as food rather than for weed control

50).

Common and Israeli Carp--

The Israeli or mirror carp is a strain of the common carp, Cyprinus
carpio. While often used to prevent algal growth in fish ponds since its
rooting activities increase turbidity (57), it is not primarily herbivorous
and ingests only a small part of the vegetation (38). Stocking rates re-
ported or recommended to control the green filamentous alga, Pithophora, in
ponds, ranged from 62-123/ha for fish of unreported size to those 12-23 cm
long (39, 40, 58, 59). Other studies recommended 224-336 kg of fish/ha for

control of this alga (60).

The ability of the common carp to control Pithophora in fish ponds in
the southeastern United States has been cited as justification for its in-
troduction (61). Neither of these fish may be acceptable in lakes because of

the threat of increased turbidity.

14


Domestic geese can be effective in clearing small ponds of duckweed (14)
and have been sucessful in Hawaii in controlling aquatic grasses after ef-
forts at physical and chemical control failed (324). While geese were con-
sidered potentially useful in Guyana, they were a threat to rice fields (73).

Swan, unlike geese, spend most of their time in the water. They consume
duckweed, filamentous algae and submerged aquatics, and can prevent estab-
lishment of cattails. They have been used in some small city water reser-
voirs to control excessive plant growth (Van Deusen, pers. comm.). One pair
of swan per 0.2-0.4 ha of pond surface represents a possible practical solu-
tion to excessive plant growth in suitable situations (72, 325, 326). The
posse excessive nutrient loading of the water by waterfowl must be con-
sidered.

Mammals

Nutria--

The nutria (Myocaster coypu) has been introduced in the Near East to
control narrow leaf cattail (Typha angustata), reeds (Phragmites communis)
and smartweed in ponds (57). It has been recommended on an experimental
scale in southeast Asia (253), and has cleared reedbeds in Britain (327). In
Cameroon, Africa, 30 young nutria completely cleared a 0.53 ha pond overgrown
with water grass (Eichinochla) in 14 months (299). Nutria breeding in carp
ponds can significantly increase fish production by destroying the emergent
vegetation (328).

Ehrlich (329) studied a series of ponds in Poland and Israel in which
nutria had depleted bulrush, reeds and cattails. One pond of 8 ha was stock-
ed with over 500 nutria in the autumn; emergent plant growth had disappeared
by the following summer. The coarse vegetation was shredded and became
available for further disintegration by carp, aquatic invertebrates and other

forms.

The development of a Polish bog lake was reversed with nutria (330). A
fenced area of 130 ha with only 2-3 ha of free water surface was stocked with
200-750 nutria per year from 1956 to 1960. The animals were completely
removed by trapping during the winter. The reeds were depleted and by 1959
over 1] ha of the area was clear. Depth gradually increased and the catch of
fish increased significantly. Wind, flow, and local biological factors had
previously been unable to prevent filling of the lake basin; the scouring
action and destruction of the vegetation by the nutria, however, established
a balance between filling and emptying of the basin.

While the harvestable pelt and meat of the nutria may represent a
potential source of income to developing countries (57, 253, 299), the low
value of the pelt and the animals' destructive burrowing and omnivorous

feeding habits mitigate against its use (73).

Manatee-- . . ;
The manatee, Trichechus manatus, a voracious totally herbivorous aquatic

mammal, may be a benefit in the tropics where food production is often

31


48.

49.

50.

51.

52.

53.

54.

55.

56.

57.

58.

59.

60.

Sobolev, I. A. 1970. Food interrelationships of young grass carp,
silver carp and carp reared jointly in ponds in Belorussia. Jd,
Ichthyol. 10(4):528-533.

Ospuszynski, K. 1968. Carp polyculture with plant feeding fish:
grass carp (Ctenopharyngodon idella Val.) and silver carp
(Hypophthatmichthys molitrix Val.) Bull. Acad. Pol. Sci. 16 (11):

Krupauer, V. 1971. The use of herbivorous fishes for ameliorative
purposes in central and eastern Europe. Proc. Int. Symp. on Aqua-
tic Weeds. Oxford. 3:95-103.

Sorokin, I. I. and D. A. Panov. 1968. Experimental determination of
food requirements of silver carp larvae and young by means of cl4.
Akad. Nauk SSSR. Biol. Sci. Sect. 182(1-6):521-523.
(Translation)

Panov, D. A., Y. 1. Sorokin and L. G. Motenkova. 1969. Experimental
study of young silver carp (Hypophthalmichthys molitrix). Prob.
of Ichthyol. 9(1):101-112.

Tang, Y. P. 1960. Reproduction of Chinese carps Ctenopharyngodon
idella and Hypophthalmichthys molitrix in a reservoir in Taiwan.
Jap. J. Ichthyol. 8(1/2):1-2.

Vestnik Akademii Nauk SSSR. 1970. The use of herbivorous fish in fish
farming and in the weeding of reservoirs. 11:26-30. (Sport Fish.
Abstr. 14055, 1971)

Verigin, B. V. 1971. Results of work on acclimatization of Far Eastern
phytophagous fishes and measures for their further assimilation and
study in new regions. (Sport Fish. Abstr. 14417, 1972)

Vestnik Akademii Nauk SSSR. 1970. Utilization of herbivorous fish in
fish management and amelioration of water basins. 11:26-30.
(WRSIC Abstr. W71-09163)

Pruginin, Y. 1968. Weed control in fish ponds in the Near East. FAO
Fish. Rep. 44(5):18-25.

Grizzell, R. A. and W. W. Neeley. 1962. Biological controls for water-
weeds. Proc. North American Wildlife and Natural Resources Conf.

27:107-113.

Hogan, W. D. 1969. The crisis of our aquatic environment. Hyacinth
Control J. 8:45-47.

Sills, J. B. 1970. A review of herbivorous fish for weed control.
Prog. Fish Cult. 32(3):158-161.

51


. Both the larvae and the adult of N. eichhorniae feed upon the hyacinth
with two generations Per year under optimal conditions (81). The effective-
ness of this species in Florida is being evaluated (91, 92) and populations
are approaching control levels at some sites (88, 93). N. eichhorniae is
also being stocked in Texas where its use will apparently be restricted to
southern areas of the state because of temperature limitations (94). Bene-
fits derived from the successful control of water hyacinth by N. eichhorniae
would include the opening of large water areas for recreation, more efficient
water distribution and flood control, a reduction in mosquito population and
reduction or elimination of chemical and mechanical weed controls (8).

Agasicles--

The flea beetle (Agasicles hygrophila) appears to be the most effective
insect introduced for the control of alligator weed (Alternanthera philo-
xeroides) in the United States (95). Feeding and egg laying are related to
chemical stimulants produced by the plants (96). Both the adults and larvae
feed upon the plant and thus suppress its growth by inhibiting photosynthe-
sis. The life cycle is about 25 days, with 5 generations per year in the
vicinity of Buenos Aires (97). Studies have been initiated to determine if
peak beetle density coincides with minimum plant carbohydrate reserves (98).

The flea beetle was first introduced into the United States in the
Savannah Wildlife Refuge, Georgia, in 1964 (99, 100, 101). Introduction into
California the same year was not successful (100). The first introduction
into Texas was in 1967 (102) with later introduction into other Texas areas
(94). A. hygrophila was successfully released and established in Florida in
1965 (103). Since that time alligator weed has decreased with increases of
the insect (104, 105). The flea beetle is now found from South Carolina to
Florida and Alabama to Texas (106). Introduction of A. hygrophila into India
for testing has also been suggested (107).

The flea beetle has destroyed extensive areas of alligator weed in
several Texas areas (108, 109, 110) and along the Peace River in Florida
(111). The latter state has been the site of its greatest success, probably
due in part to its ability to overwinter here. However, the insect has not
been uniformly effective in all areas of the southeastern United States,
perhaps because variations in plant growth or nutrition have altered the
alligator weed's attractiveness (112). Damage to the alligator weed is not
noticeable when beetle density is less than about 43-54/m? of level area
(106, 113). Severe damage has been reported at adult population levels of 54-

108/m? (95).

The most important limiting factor in using the flea beetle for bio-
logical control is climate; the organism is sensitive to cold temperatures.
Frost prevents regrowth of the plant but also severely limits populations of
Agasicles, thus an insufficient number of insects are present when the plant
7g most susceptible (109, 110). The number of overwintering adults deter-
mines whether population densities are sufficiently high for effective con-
trol (106), since most control of alligator weed is achieved in spring (85).
A new stock of beetles collected south of Buenos Aires may be better able to
withstand winter in the cooler climates than those from previous releases

(114).
7


466.

467.

468.

469.

470.

47).

472.

=
~
2

474,

475.

Rintz, R. E. and T. E. Freeman. 1974. Fusarium roseum pathogenic to
water hyacinth in Florida. p. D-3. In Gangstad, E. 0., T. E.
Freeman, R. W. Zettler, R. E. Rintz, R. Charudattan, K. Conway, and
H. E. Hill. Aquatic weed control with plant pathogens. Aquatic
Plant Control Program. Tech No. 8. Army Eng. Waterways Exp. Sta.,
Vicksburg, Miss.

Charudattan, R. 1973. Pathogenicity of fungi and bacteria from India
to hydrilla and waterhyacinth. Hyacinth Control J. 11:44-48.

Charudattan, R. 1974. Survey for diseases of Hydrilla verticillata and
other aquatic weeds in southern India. p. F3-F10. In Gangstad, E.
0., T. E. Freeman, F. W. Zettler, R. E. Rintz, R. Charudattan, K
Conway, and H. E. Hill. Aquatic weed control with plant pathogens.
Aquatic Plant Control Program. Tech. Rep. 8. Army Eng. Waterways
Exp. Sta., Vicksburg, Miss.

Charudattan, R. and C. Y. Lin. 1974, Isolates of Penicillium, Asper-
gllus and Trichoderma toxic to aquatic plants. Hyacinth Control
12:70-73.

Hayslip, J. F. and F. W. Zettler. 1973. Past and current research on

diseases of Eurasian watermilfoil (Myriophy11um spicatum L.)
Hyacinth Control? J. 11:38-40.

Loveless, A. R. 1969. The possible role of pathogenic fungi in local
degeneration of Salvinia auriculata Aublet on Lake Kariba. Ann.

Appl. Biol. 63(1):61-69.

Patten, B. C. 1973. Need for an ecosystem perspective in eutrophica-
tion modeling. p. 83-87. In Middlebrooks, E. J., D. H. Falken-
borg, and T. E. Maloney (eds.) Modeling the eutrophication process.
Utah Water Res. Lab., Utah State Univ., Logan.

. O'Brien, W. J., and F. DeNoyelles. 1974. Relationship between nutrient

concentration, phytoplankton, density, and zooplankton density in
nutrient enriched experimental ponds. Hydrobiologia 44(1):105-
125.

Haertel, C. 1975. Effects of zooplankton grazing on nuisance algal
blooms. South Dakota State Univ., School of Arts, Brookings.
Notice of Research Project, Smithsonian Science Information Ex-
change, Washington, D. C. SIE No. GUW-4384.

Taub, F. B. 1974. Culture-computer model of aquatic communities. Univ.
of Washington, School of Fisheries, Seattle. Notice of Research
Project, Smithsonian Science Information Exchange, Washington, D.
C. SIE No. GMA-1601-1.

84


Uronema, Coleochaete, and Radiofilum (419). Viruses lysing Chlorella
pyrenoidosa have been reported (420, 421) and a possible virus infection has
been studied in Oedogonium (422). The red alga Sirodotia tenuissima has an
associated virus (423).

Control of Macrophytes

Little research has been carried out on viruses as potential biological
controls of aquatic vascular plants. A virus stunting disease of alligator
weed (424) has not been effective when allowed to transmit naturally (425).
However, virus stunt may have some potential in controlling water hyacinth
(426). A virus may have been responsible for a 95 percent decline in Eurasian
watermilfoil in Cheasapeake Bay from 1965 to 1967 (427, 428). In the early
1970's, however, while watermilfoil continued to show disease symptoms,
presence of a virus could not be demonstrated; hence final results were
inconclusive (Southwick, pers. comm.).

BACTERIA

Control of Blue-green Algae

The relationships of blue-green algae and bacteria have been reviewed by
Whitton (429). He pointed out that although the addition of bacteria which
produce antagonistic substances is frequently suggested for controlling
nuisance algae, such bacteria are already widespread in nature. As with
viruses and other biological controls, however, the use of bacteria as poten-
tial control agents would have the advantage of eliminating the need for
chemical algicides; the closer physiological and evolutionary relationships
of bacteria and blue-green algae are also part of the rationale for proposing
them as controls (430).

Bdellovibrio bacteriovorus is an endoparasitic bacterium under study
(430) with the potential for large-scale blue-green algae control (431).
Inhibition of oxygen evolution in Phormidium and Microcystis has been demon-
strated (432, 433) and one B. bacteriovorus cell is capable of producing
sufficient lytic factor to inhibit 75 Phormidium luridum cells (434).

Myxobacteria capable of lysing many species of blue-green algae have
been isolated by Shilo (435) and Daft and Stewart (436). A bacterium which
inhibited the growth of Nostoc sphaericum was isolated in Germany (437).
Lysis of vegetative blue-green algae cells occurred within 30 minutes after
the attachment of a bacterium isolated by Daft and Stewart (438). Bacteria
which can lyse green algae have also been isolated (439, 440). Wood (418)
has designed studies to find and test naturally occurring bacteria that may
be effective as biological controls. The role of bacteria in the disappear-
ance of blue-green algae blooms and the feasibility of their use is also
being investigated by Ensign (416).

Control of Macrophytes

Research reports on bacterial diseases for potential control of aquatic
macrophytes are rare. Freeman et al. (377) have not been able to isolate a

38


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Cannon, R. and M. Shane. 1972. The effect of antibiotic stress
on protein synthesis in the establishment of lysogeny on Plectonema
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Shane, M. S., W. S. Vincent, R. E. Cannon, and H. A. Glass. 1974.
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Safferman, R. S. and M. E. Morris. 1964. Control of algae with viruses
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Guttman, H. M. 1973. A critical test of methods for isolation of
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Ensign, J. C. 1974. Lysis of blue-green algae by bacterial enzymes and
their possible use in controlling algal blooms. Univ. of Wisconsin,
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denifer, F. G. 1974. Biology of the blue-green algal viruses. Rutgers,
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343-348.

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Bayley, S., H. Rabin, and C. H. Southwick. 1968. Recent decline in the
distribution and abundance of Eurasian milfoil in Chesapeake Bay.
Chesapeake Sci. 9(3):173-181.

Whitton, B. A. 1973. Interactions with other organisms. p. 415-433.
In The biology of blue-green algae. Carr, N. G., and B. A. Whitton
Teds.) Botanical Monogr. Vol. 9. Univ. of Calif. Press.

Burnham, J. C. 1975. Bacterial control of aquatic algae. p. 120-125.
In Brezonik, P. L. and J. L. Fox (eds.) Proc. symp. on water
quality management through biological control. Univ. of Florida and
U. S. Environmental Protection Agency, Gainesville, Jan. 29-31.

80


against tough emergent plants. Fish culture ponds are routinely cleared of
aquatic weeds by stocking amur fingerlings at a rate of 247-1,235/ha. Lakes
are generally stocked at the rate of twenty-five 20-25 cm fish/ha, resulting
in approximately 112 kg of fish/ha by mid-summer, sufficient for control
during that year.

The amur was stocked in a 29 ha Iowa lake to evaluate its effectiveness
in weed control (243). Fish averaging 31 cm and 380 g were stocked at a
rate of 18/ha. They consumed 37 metric tons of vegetation, halving the
standing crop of weeds by the latter part of the summer

The Tennessee Valley Authority has initiated a multidisciplinary study
on the amur in the Tennessee Valley (185). Shleser and Yeo (244) are devel-
oping sterile amur in California for weed control and are determining feed-
ing habits, behavior and stocking rates. Evaluation of the amur as a weed
control agent in Puerto Rico is presently being carried out by Benn and
Rushing (245); Lembi (pers. comm.) is presently conducting field studies with
the amur in fish hatchery ponds in Indiana.

Use in foreign countries--The amur has been successfully used to control
weeds in Lake Obsyjtn, Sweden (201, 202, 246, 247). The 4.6 ha lake was
covered with Eurasian water milfoil; dry weight in 1969 was 16 metric tons.
Two hundred-fifty amur averaging 380 g were introduced in May, 1970; after
100 days, the average fish weight was 1,030 g and only 7.3 metric tons (dry
weight) of milfoil remained. The average weight of the amur after ice-out in
1971 was 766 g.

Acclimatization of the amur in the U.S.S.R. started in the 1930's (248)
and it has since been used to reduce aquatic plants in coolant reservoirs
(249). Fifty to 100/ha were sufficient to clear one reservoir of weeds; no
reinfestation had occurred after seven years (250). In Turkmenia, 375 amur
(total weight 55 kg) cleared 22 metric tons of milfoil from a 1.8 ha area in
110 days (251). Amur introduced into Czechoslovakian irrigation canals have
eliminated the vegetation (17).

Seventeen kg of amur in an English pond increased to 173 kg in 20 weeks
while consuming about 6,804 kg of weeds (252). This fish has also been used
in London water reservoirs (Anon., cited in 37) and has been introduced into
New Zealand (205; Chapman, White, cited in 17).

The amur has long been used to control weeds in China (Lin, cited in
253) and Japan (Araki, cited in 61). It has been imported for weed control
in Pakistan (254), India (Avault, cited in 14), Malaysia (251) and Mexico
(255). Its introduction into Sudan is planned to control macrophytes and the
snail host of bilharzia (schistosomiasis) (196). It was also recommended as
a potential biological control and an additional food source in the Chambal
River irrigation system in India (195) and proposed as a control in irriga-
tion systems in the U.S.S.R. (54, 56). Introductions are planned in Lake
Carriazo, Puerto Rico (Goitia, cited in 17). The problems associated with
production of amur in cold climates will be investigated in Sweden (256).

25


SECTION 1
INTRODUCTION

Biological methods have often been advocated as having great potential
for effective, economic and permanent control of undesirable aquatic species
(1,2) and as a desirable alternative to the use of pesticides and herbicides
(3). Biological control has the advantage of continued pressure without
additional applications (4), reported low cost and ease of application and
minimal personnel requirements (5). Some general requirements for biological
control agents include an ability of the selected species to survive and
maintain themselves, an ability to reduce the problem species and a capabi-
lity of co-existence with native species in their new environment (6).

The primary objective of biological control is not necessarily the
elimination of a species, but its reduction to a nonnuisance level; both the
introduced and the target species must become compatible parts of the eco-
system (7). Control is successful when equilibrium between the predator and
prey species is reached, tending to restore the balance to that which existed
prior to the appearance of the pest species (8).

Many of the principles of classical biological control have been re-
viewed by Sailer (9) who emphasized the stability of a diverse ecosystem. For
example, species introduced for control purposes can become an integral part
of the ecosystem and add to its diversity, whereas chemical control can
reduce diversity by eliminating species. Biological methods integrated with
chemical or mechanical control procedures often produce better results than
either method used alone. Perkins (10) stated that insects used in conjuc-
tion with chemical and some form of habitat manipulation might be needed for
optimal control of the water hyacinth. Crowder (11) recommended an initial
removal of problem weeds by mechanical means followed by the introduction of
a biological control organism. However, he emphasized that the benefits of
this combination method may be temporary if the waters continue to receive

nutrients.

Increased interest in aquatic biological control has been indicated by
recent conferences and reviews. A 1974 Conference on Lake Protection and
Management at the University of Wisconsin and a Lake Management Conference at
Purdue University in 1975 dealt in part with managing aquatic environments
with biological controls. A symposium at the University of Florida in 1975
on Water Quality Management through Biological Control was concerned entirely
with this subject; its Proceedings are an excellent compilation of current

approaches (12).


evident as sunken lesions which enlarge and coalesce, becoming zonate with
brown bands (377). The symptoms, isolation, morphology, culture and patho-
genicity of this fungus have been described by Rintz (459). A. zonatum
apparently does not retard the rapid growth of the hyacinth; however effects
when applied at high concentrations are being explored (377, 459, 460). It
may have greater potential when used in conjunction with the weevil, Neoche-
tina eichhorniae (425, 461) and the mite, Orthogalumna terrabrantis (462,
463).

Alternaria eichhorniae is an Indian fungus which may have some utility
as a water hyacinth control (464). Culture methods have been developed which
demonstrate its pathogenicity (465); it is still under investigation (76,
462, 463). A form of Fusarium roseum, a weak pathogenic fungus that causes
vascular browning of the water hyacinth was isolated in Florida (457, 466).
It may not be of value unless it is augmented by some additional control
method (377).

The rust Uredo eichhorniae attacks the water hyacinth in Argentina and
has encouraging possibilities as a control in this country (425). Helmin-
thosporium stenospilum is also highly destructive to the hyacinth; however,
this fungus is a sugar cane parasite in some areas and its use may be re-
stricted (425).

Fungi pathogenic to hydrilla in India are currently being studied at
the University of Florida (467, 468). In addition, species of Penicillium,
Aspergillus and Trichoderma associated with diseased hydrilla produce toxins,
including oxalic acid. While the use of purified fungal toxins would have
advantages over handling live pathogens, the extreme toxicity of purified
fungal oxalate may preclude its use in hydrilla control (469). The RhEa
strain of Rhizoctonia solani only occasionally.infects hydrilla (458).

Fungi attacking other aquatic macrophytes have received less attention.
Hayslip and Zettler (470) reviewed the past and current research on Eurasian
watermilfoil; in tests they obtained only limited success with fungi reported
as pathogens on other plants. The control potential of a species of Alter-
naria isolated from alligator weed in Puerto Rico is being studied (461).
Salvinia auriculata may be controllable by a parasitic fungus (471) and
although the RhEa strain of R. solani is strongly pathogenic to water lettuce
Pistia stratiotes), further work is needed to insure that it will not infect
desirable species (458).

40


Control Of inseCtS 1... ccc cece eee cece eee eee e neers 33

Control OF FISH Lecce cece cece cece eee eee e teen en enees 33

5. Use of Pathogens 1... cece ccc c cece eee eee eee eee eee eee ene 35
VITUSES Cece cece e eect cere eee e eee nent eee een enes 35

Control of blue-green algae ...... ce cece e eee eee 35

Control of other algae .... cece eee c cece ee eee tees 37

Control of macrophyteS ....... cece cece eee eee ee 38

Bacteria .o ieee cece eee cece eee eee teen een eee 38

Control of blue-green algae ........ cee cece eee eee 38

Control of macrophytes ........ cece cece e eee e eens 38

Control of fish wo... cece cece cece 39

Fungi ........ Peer eee e eet ne nee tee eee e eee ee eeereneees 39

Control of phytoplankton ....... ccc cece eee eee eee 39

Control of macrophytes ........ cece cece ee ence eee 39

6. Biomanipulation ......c cece cee cee eee cece eee e encase 4]
GraZING Levee cece cece cece eee eee eee eee eee e teen enee 41

Fish Stocking .... ccc eee cece cece cece e eee e eee e eee e ee nees 42

Fish sterilization and hybridization ...............04. 42
Fertilization oo... cece cece eee cece eee eee eee ee 43
Competition co ccc cece cece cece e cece e eect eee e eee 43
Allelopathy and autoinhibition ......... cece cece ee eee 44
Environmental manipulations ........ceeeeeeeeeeee eee eee 44

7. Economics of Biological C000) ho 0) 46
REFELENCES Lecce ccc eee cece eee ee eee ee ee eee eee EEE Ee eae 47

viii


however, the bass increased significantly (368). White bass (Roccus chrysops)
heavily consume gizzard shad and threadfin shad (Dorosoma petenese) in open
waters (369). Northern pike (Esox lucius) and bluegills were concluded to be
a good stocking combination in Nebraska farm ponds (370). Northern pike
stocked at the rate of 62 15 cm fish/ha or 124 5 cm fish/ha were recommended
to control overabundant panfish in Colorado reservoirs (371).

Northcote (358) considered fish stocking as a science archaic in terms
of numbers, size and proper timing of introduction of fish into any particu-
lar lake. Restriction of the practice to new and reclaimed lakes and to the
introduction of a desirable species not already present has been recommended
(Kinney, cited in 372). According to Dunst et al. (17), a successful preda-
tor stocking program must consider food preference, the size of the prey, the
size of the target population and the availability of the prey.

Fish have many predators in addition to other fish, such as bullfrogs,
turtles, mudpuppies, snakes, birds, mink and otter; early stages are also
preyed upon by copepods, hydra, crayfish and insects (373, 374). Since some
of these predators may require control to protect native fish populations
(373), their introduction may also serve to control undesirable fish popula-
tions.

Dunst et al. (17) emphasized that the practice of introducing various
species which serve as fish food has not been evaluated from the standpoint
of lake restoration and needs further study. For instance, freshwater shrimp
(Mysis relicta) have been introduced into Kootenay Lake, British Columbia, to
augment the food supply of rainbow trout (Salmo gairdneri) (358), and bulk
quantities of mysids have similarly been introduced into a Russian reservoir
to develop a food supply for young “pike perch" (359).

34


of an inability to ingest Aphanizomenon (28).

Although the survival of colonial species of blue-greens is often
enhanced because they are less readily consumed by most grazers (29), the
copepod Thermocyclops hyalinus from Lake George, Uganda, consumes Microcyctis
and can assimilate about 35-50 percent of the ingested carbon (30). Rotifers
have not been utilized or suggested for biological control purposes. However,
Lindia euchromatica is apparently dependent upon the blue-green Gloeotrichia
for food (31) and Proales werneckii parasitizes the filamentous green alga
Vaucheria (32).

Research into species able to ingest blue-greens may be worthwhile,
however, the successful use of zooplankton to alter algal abundance may
involve manipulations of both zooplankton and fish populations. This is
covered in a later section.

Fish

Tilapia--

Tilapia, fishes native to Africa, the Jordan Valley, Central and South
America, South India and Ceylon (33) have been used or recommended in warm
climates to control algae. Most instances of control, however, have involved
very high stocking rates. Their acceptability for use in lakes is therefore
limited not only by colder temperatures, but by the threat of over-population
as well.

The diet of the Java tilapia (T. mossambica) is predominantly filamentous
algae and diatoms (34); however, the latter remain relatively intact through
the digestive tract (33). Prowse (36) considered this species suitable for
phytoplankton control at temperatures above 13 C but emphasized the need for
a predator to keep populations in check. It has cleared farm ponds in
Puerto Rico of the algae Spirogyra, Chara and Nitella (37) and controlled
Pithophora in the southeastern United States (38, 39). Avault (40) reported
a stocking rate of 2,470- 4,940 fish/ha to control the latter alga.

The diet of the Congo tilapia (T. melanopleura) varies with different
habitats; in Rhodesia it consumes about 64 percent macrophytes and 19 percent

macroinvertebrates (34). It has controlled Pithophora, Spirogyra and Rhizo-
clonium in ponds at a stocking rate of 3,700 - 4,940 fish/ha (39, 40).

The Nile tilapia (T. nilotica) has controlled Pithophora in ponds when
stocked at 1,975-4,940 fish/ha (40, 41). Pollard et al. 42) reported that
it has a greater potential for nutrient removal from an Oklahoma Lake used
for power plant cooling than hybrid buffalo (Ictiobus) or channel catfish
(Ictalurus punctatus). The Nile tilapia, unlike other species, can digest
blue-green algae (30, 43) and can assimilate 70-80 percent of the ingested
carbon from Microcystis and Anabaena (44, 45).

The blue tilapia (T. aurea) has been stocked in Lake Kinneret, Israel,
to limit algal growth; results are inconclusive (Serruya, cited in 17). It
demonstrated little potential for algae control in Florida and its

13


TABLE 1 (continued)

Problem or Project

Solution or Proposed Treatment Location Results or Remarks References
Fungus-Acremonium zonatum Florida Under study, may have potential 425, 461
if used in conjuction with 462
weevils or mites
Fungus -Alternaria eichhorniae India Under study, much potential 425
Rust-Uredo eichhorniae Argentina Under study 467, 468
Hydrilla Fungi South U.S.A. Under study 467, 468
C. BIOMANIPULATION
Rooted aquatics Slender spikerush (Eleocharis California May eliminate undesirable 507, 508

Excessive
macrophytes

Ill FISH

Bluegills in
ponds

Bluegills in
Takes

Perch and Bass

Stunted panfish

acicularis)

Fertilization (induced
phytoplankton turbidity)

Fertilization (induced
phytoplankton turbidity)

A. PREDATION

Spotted gar (Lepisosteous
oculatus )

Northern pike (Essox lucius)
Largemouth bass (Micropterus
Salmoides )

Muskellunge (Essox mosquinongy)

Walleyes (Stizostedion vitreum)

New Jersey

Kansas

Alabama

Nebraska

Ohio

Wisconsin

Wisconsin

species through competition,
under study

Objectionable growth in 18 ha
Jake eliminated after two-year
program, boating and fishing
improved

Vegetation controlled in 16 ha
lake, total of 347 kg/ha of

ammonium sulfate and 226 kg/ha
of triple superphosphate used

Not controlled

Successful control

Not controlled

Reduced to unmeasurable level

within a year

Ineffective

501, 502, 503

504

365

370

366

368

363

(continued)


December, 1975
Biological Abstracts
BA data base - searched February, 1975
BA current awareness search - March, 1975 to
February, 1976
Bioresearch Index data base - searched February, 1975

Fish and Wildlife Reference Service data base - searched
February, 1975

Defense Documentation Center data base - searched November,
1974; April, 1975; June, 1975; July, 1975

Eutrophication Abstracts - No. 1 (March, 1969) to No. 47
(March-April, 1975)

Algal Abstracts - Vol. I (to 1969); Vol. II (1970-1972)

Sport Fishery Abstracts - Vol. 5 (1960) to Vol. 20 (1975)

Smithsonian Science Information Exchange, Inc. data base -
Searched October, 1974; March, 1975; June, 1975; September, 1975

Institute for Scientific Information, Inc.
Current Contents - Agriculture, Biology and Environmental Sci-
ences - January, 1974 to September, 1975

The invaluable assistance of C.R. Jung and B.M. McCauley in searching
the literature is gratefully acknowledged. Valuable criticisms were fur-
nished by J. Shapiro, K.W. Malueg, D.P. Larsen, C.F. Powers, W.D. Sanville,

and D.T. Specht.

Thanks are extended also to the Smithsonian Science Institute

Exchange, Inc. for permission to cite a number of Notices of Research Projects.


193.

194,

195.

196.

197.

198,

199,

200.

201.

202.

203.

204.

Chaudhuri , H. 1966. Breeding and selection of cultivated warm-water
Fishes in Asia and the far East--a review. FAO Fish. Rep. 44(4):

Food and Agriculture Organization of the United Nations. 1971. Culture
of Chinese carps and weed control. FAQ Aquacult. Bull. 3(2):4.

Blackburn, R. D. 1971. Aquatic weed problems, control, research needs
and fishery potential in the Chambal command area of Rajasthan,
India. Appendix G, 21 p. In: Gangstad, E. 0., A. E. Seaman, and
M. L. Nelson. 1971. The potential growth of obnoxious aquatic
plants and practical systems of control in the Republic of India.
Office of the Chief of Eng. (Army) Washington, D. C.

Food and Agriculture Organization of the United Nations. 1975. Introduc
tion of carps into Sudan. FAO Aquaculture Bull. 7(1-2):25.

Chapman, U. J. and B. J. Coffey. 1971. Experiments with grass carp in
controlling exotic macrophytes in New Zealand. Hidrobiologia (Ro-
mania) 12:313-323.

Baily, W. M. 1975. Operational experiences with the white amur
in weed control programs. p. 75-78. In Brezonik, P. L. and J. F.
Fox (eds.) Proc. symp. on water quality management through biologi-
cal control. Univ. of Florida and U.S. Environmental Protection
Agency, Gainesville, Jan. 29-31.

Kilgen, R. H. and R. 0. Smitherman. 1973. Food habits of the white
amur (Ctenopharyngodon idetla) stocked in ponds alone and in
combination with other species. p. F3-F13. In E. 0. Gangstad, J.
J. Raynes and R. M. Burress, et al. Herbivorous fish for aquatic
Plant control. Aquatic Plant Control Program, Tech. Rep. 4, U.S.
Army Eng. Waterways Exp. Sta., Vicksburg, Miss. (NTIS AD-765 437)

Edwards, D. J. 1973. Aquarium studies on the consumption of small

animals by o-group grass carp, Ctenopharyngodon idella (Val). J.
Fish. Biol. 5(5):599-605.

Ahling, B. and A. Jernelbv. 1971. Weed control with grass carp
in Lake Osbysjén. Swed. Water and Air Pollut. Res. Lab. Publ. B.

94a. 15 p.

Ahling, B. and A. Jernelév. 1971. Vaxtbekampning med grdskarp
i Osbysjtn. Vatten 2:253-264, (English Summary)

Hickling, C. F. 1966. On the feeding process in the white amur,
Ctenopharyngodon idella. J. Zool. 148(4):408-419.

Stroganov, N. S. 1963. Food Preferences of the grass carp. (Biol.
Abstr. 46(3) No. 9759)

63


The flea beetle is effective in consuming alligator weed treated with
herbicides (115) and actually prefers young regrowth (116). Added contro]
has thus been achieved by using the beetle in conjunction with applications
of 2, 4-D (117, 118, 119). Herbicidal treatment followed by the release of
25-50 beetles/ha was more effective than using overwintering beetles alone
(120). This integrated approach to aquatic weed control has been stressed by
the Corps of Engineers (121) and others (95) and is also under study as a
means to control water hyacinth (122).

Alligator weed, as it is suppressed by the flea beetle, becomes less
able to compete with the water hyacinth and in some areas is being replaced
by it (97, 106, 123).

Other Coleopterans--

Several other coleopterans (beetles) may have biological control po-
tential. Bagous lutulosus appears to be specific in attacking hydrilla
(Hydrilla verticillata) in Pakistan (124). Three curculinonids and a ge-
lechiid, also from Pakistan, have peen suggested as possible controls of
watermilfoil (Myriophyllum spp.) (125). Galerucella nymphaeae may be able
to limit the growth of water lilies in Russia (Nymphaea candida, Nuphar
luteum) (126). The weevil Neohydronomus pulchellus is a promising candidate
for introduction into the United States for control of water lettuce (Pistia
stratiotes) (127). Litodactylus leucogaster has the potential for reducing
seed production in Eurasian watermilfoil (Myriophyllum spicatum) (128, 129).

Vogtia--

The alligator weed stem borer (Vogtia malloi) was introduced into the
United States from Argentina in 1971 and has become established at several
locations from North Carolina to Florida (104, 105, 130). This moth promises
to be one of the most widespread biological control mechanisms of alligator
weed (105). It is presently important in its control in South Carolina (131)
and is the subject of continuing study in Florida (114), where it has de-
monstrated its effectiveness by reducing the number of aerial stems from 565
to 43/m* in four generations (130). In Argentina, it produces three to four
generations per year (132).

V. malloi may be effective in more northern areas where the alligator
weed Flea beetle cannot overwinter and so will supplement the biological
control of this weed (123). It is able to complete its life cycle only on
alligator weed. The larvae burrow into the plant immediately after the egg
hatches. Early larvae are confined mostly to the stem cavity while older
larvae become roving stem borers. They pupate within the stem and emerge
through pre-cut windows (110, 132).

Acigonia--

g The moth Acigonia infusella is the subject of a number of feasibility
studies in Florida (88, 131) and is under consideration for introduction into
the United States for water hyacinth control (93). Since this insect can
also complete its life cycle on pickerel weed (Pontederia lanceolata) (75),
its release has been delayed (133). In the hyacinth, the eggs are laid in
leaf crevices and the larvae bore into the petiole; the adult emerges from

18


TABLE 1. SELECTED LIST OF PROPOSED OR ACTUAL INSTANCES OF BIOCONTROL

Problem or Project

Solution or Proposed Treatment Location Results or Remarks References
I, ALGAE
A. GRAZING
Anabaena blooms Amoeba Georgia Under study 20, 21
Microcystis blooms Ochromonas dancia Laboratory Under study 22, 23
Phytoplankton standing Mississippi silversides California Had little impact 62; R. Brown
crop (Me udens ) Pers. Comm.
Silver Carp (Hypothalmichthys U.S.S.R. Proposed 54, 56
nolitrix), Thickhead
Aristichthys nobilis)
Algal growth Silver Carp Israel Inconclusive Serruya, cited
in
Pithophora Israeli Carp (Cyprinus carpio) Georgia, Recommended or reported stocking 39, 40, 58, 59
in Ponds Arkansas rates of 62-123/ha
Tilapia Mossambica Alabama Controlled at stocking rates of 40
2,470-4,940/ha ,
Cladophora in Mullet (Mugi i . in 5 58
—gcophors. lugil cephalis) S. Carolina Cladophora almost gone in
luckponds months, control remained
‘infested
ree aes Swan (Cygnus olor) ttichigan Stocked at rate of one pair per 71, 326
ponds 0.2-0.4 ha
B. PATHOGENS
Tueegreen Virus~cyanophages ULS.S.R. Reported to have lysed blue- Topachevsky, cited
‘ green algal scum in 413
Cyanophages Laboratory Suggested as controls, under study 395, 397, 411, 412
Bacteria-Bdel lovibrio Laboratory Has potential, under study 43)

bacteriovorus.

(continued)


were introduced into Lake Gbsyjon, Sweden. However, ciliates decreased in
the zooplankton and there was a tendency toward more cleanwater associated
organisms in the benthos (201, 202).

Feeding, diet and assimilation--The specialized pharyngeal teeth of the
amur allow small specimens to exploit soft vegetation while large fish can
utilize tough, fibrous material (203). They feed at intervals of only 5-7
days at 3-6 C, and more intensively above 16 C; food selectivity increases at
lower temperatures (204). A greater variety of plants is consumed as the
temperature increases, and the fish grow larger (48, 205).

The literature contains numerous reports of food preferences. Although
these plants vary according to location or specific feeding trial, common
cattails (Typha latifolia) and water hyacinth are frequently avoided (206,
207, 208). The amur has been considered a feeding "opportunist" (209) and in
some cases may prefer the filamentous algae Cladophora and Spirogyra to
aquatic vascular plants (210). Avault, Smitherman and Shell (61) Tisted the
preference in descending order for twelve plant species in Alabama ponds as
follows:

Chara (Chara), Southern naiad (Najas guadalupensis), pondweed (Potamogeton
diversifolius), slender spikerush (Eleocharis acicularis), coontail, water
hyssop (Bacopa rotundifolia). elodea, Eurasian watermilfoil, vallisneria
(Vallisneria americana), water hyacinth, parrot feather (Myriophyllum
brasiliense) and alligator weed. Other preferences from the United States
have been listed for Alabama (211), Florida (212, 213) and Oregon (214).

Feeding preferences have also been reported from India (207, 215, 216),
New Zealand (197, 205), Poland (206), Czechoslovakia (208) and the U.S.S.R.
(217, 218). Preferences from other localities have been listed by Cross
(219). Krupauer (220) found over 73 species of aquatic plants in Czechoslo-
vakia were readily eaten by the amur and Bailey (198) reported that they
effectively controlled 22 species in Arkansas lakes.

The amur consumes phytoplankton and Infusoria during the first 2-4 days
of life, changing to zooplankton after 5 days (221, 222). Preferences
include Daphnia, Polyphemus, Bosmina and Scapholebris; Copepoda, Chydorus and
Ceriodaphnia are shunned (48). The fish do not become phytophagous until
they are about one month old and 2.5-4 cm in length (47, 49, 186).

Edwards (200) found that in aquaria, 7 to 11 month old amur would eat
common invertebrates and trout fry in the presence of palatable plants when
there was no cover for the prey. While the degree of predation in nature
could not be predicted from these experiments, the need for additional study
before introduction into trout spawning waters was emphasized.

The gut of the amur is only about one-fifth the length normally found in
a herbivore (223). Food passes through the fish in less than eight hours at
28-30 C, with approximately only half of the plant material being utilized
(203). Although digestion is not efficient, half of its food is sufficient
for growth. Essential proteins are obtained from growing shoots, filamentous
algae or animals (224).

23


476.

477.

478.

479.

480.

481.

482.

483.

484.

485.

486.

487.

488.

Dickman, M. 1968. The effect of grazing by tadpoles on the structure
of a periphyton community. Ecology 49(6):1188-1190.

Seale, D. B., E. Rodgers, and M. E. Boras. 1975. Effects of suspen-
sion-feeding frog larvae on limnological variables and community
structure. Verh. Int. Verein. Limnol. 19:3179-3184.

Wassersug, R. 1974. The role of anurans in the control of primary
production associated with eutrophication. Report prepared for
Eutrophication and Lake Restoration Branch, U. S. Environmental
Protection Agency, Corvallis, Oregon. 34 p.

Cole, R. A. 1975. Aquatic studies on biological control and nutrient
export in wastewater ponds. Michigan State Univ. School of Agri-
culture, East Lansing, Michigan. Notice of Research Project,
nmi thsonian Science Information Exchange, Washington, D. C. SIE
lo. GUY- .

Erickson, P. A. and J. T. Reynolds. 1969. The ecology of a reservoir.
Nat. Hist. November. p. 48-53.

Shapiro, J. 1976. Summary progress report on biomanipulation--an
ecosystem approach to lake restoration. Limnol. Res. Cent., Univ.
Minnesota. EPA Research Grant R803870010.

Limnological Research Center. 1975. Biennial Report. Univ. Minnesota.
28 p.

Ulrikson, G. U. 1969. Use and effects of cobalt 60 for sterilization
of bluegills (Lepomis macrochirus). Ph.D. Diss., Univ. of Mich.
136 p.

Stock, J. N. and 0. B. Cope. 1969. Some effects of TEPA, an insect
chemosterilant on the guppy Poecilia reticulata. Trans. Amer.
Fish. Soc. 98(2):280-287,

Chew, L. E. and J. G. Stanley. 1973. The effects of methyltestosterone
on sex reversal in bluegill. Prog. Fish Cult. 35(1):44-47.

Childers, W. F. and F. W. Bennett. 1961. Hybridization between three
species of sunfish (Lepomis). Illinois Nat. Hist. Surv. Biol.
Notes 46:1-15.

Smitherman, R. 0. and F. E. Hester. 1962. Artificial propagation of
sunfishes with meristic comparisons of three species of Lepomis and
five of their hybrids. Trans. Am. Fish. Soc. 91(4):333-347.

West, J. K. and F. E. Hester. 1966. Intergeneric hybridization of
centrarchids. Trans. Am. Fish. Soc. 95(3):280-288.

85


TABLE 1 (continued)

Problem or Project Solution or Proposed Treatment Location Results or Remarks References
C.  BIOMANIPULATION
Nuisance algae Alleopathic or heteroinhibiting Laboratory Substances produced by green 528, 529
substances alga Pandorina morum promising
Large colonial algae Zooplankton-Daphnia magna --- Suggested as algae control after 27
zooplanktivores reduced by
carnivores
Phytoplankton Zooplanktivorous fish --- Suggested as means to allow 27
zooplankton to increase and
consume phytoplankton
Pantothenic acid s+ Suggested as means to increase 27
zooplankton
Environmental manipulations oon Additions of HC1, CO, or Cl, or 27
other substances might help
shift algal populations from
blue-greens to greens. Zoo-
plankton might be increased and
algae subsequently decreased by
lowering pH
II MACROPHYTES
A. GRAZING
Overabundant Snails-Marsia Florida, 9,875-19,750 snails/ha elim- 96, 158, 159
vegetation in Puerto Rico inated submersed vegetation in
small lakes 12-18 months
and ponds
Water hyacinth Snails-Pomacea Laboratory About 100 snails eliminated 150

water lettuce

Water hyacinth

Weevil-Neochetina

Moths-Acigonia, Arzema
Mi te-Orthogalumna

Grasshopper-Cornops

Florida, Texas,
Louisiana

South U.S.A.
South U.S.A.

South U.S.A.

2,500-5000 g of plants in
29-44 days

Promising control, under study

Under study
Promising candidate

Under study

81, 82, 87, 91

87
147

87, 113, 137
(continued)


140,

141,

142,

143,

144,

145,

146.

147,

148,

149,

150.

151.

Spencer, N. R. 1971. The potential usefulness of an aquatic lepidop-

teran as a control agent for Myriophyllum spicatum. Proc. South.
Weed Sci. Soc. 24:348. (Abstr.

Lekic, M. 1970. Ecology of the aquatic insect species Parapoynx
stratiotata L. (Pyraustidae, Lepidoptera). J. Sci. Agric. Res.

Yugoslavia) 83(23):49-62.

DeLoach, C. J. and D. J. Deloach. Notes on the biology and specificity
of Samea multiplicalis, a moth attacking Pistia stratiotes in
Argentina. (In prep.

Chaudhuri, H. and K. J. Ram. 1975. Control of aquatic weed by moth
larvae. Nature 253(5486):40-41.

Johnstone, Ian M. 1967. Some aspects of the biology of Ceratophyllum
demersum. Proc. Rotorua Seminar on Water Weeds. Univ. of Auckland,
New Zealand. p. 23-27.

Agriculture Research Service. 1970. Investigations for use of insects
for control of alligatorweed, water hyacinth, elodea, and water-
milfoil. Entomol. Res. Div. U. S. Dep. Agr.

Vogt, G. B. 1973. Exploration for natural enemies of alligatorweed and
related plants in South America. p.B3-B66. In Gangstad, E. 0., S.
C. Solymosy, G. B. Vogt, L. A. Andres, and L. W. Weldon. Biologi-
cal control of alligatorweed. Aquatic Plant Control Program. Tech.
Rep. 3. Army Eng. Waterways Exp. Sta., Vicksburg, Miss.

Cordo, H. A. and C. J. DeLoach. 1975. Ovipositional specificity and
feeding habits of the water hyacinth mite, Orthogalumna terebrantis,
in Argentina. Environ. Entomol. 4(4):561-565.

Cordo, H. A. and C. J. DeLoach. 1976. Biology of the water hyacinth
mite in Argentina. Weed Sci. 24:245-249,

Phillippy, C. L. 1970. Biological weed control research being con-
ducted by the Florida Game and Freshwater Fish Commission. p. 28-
38. In Proc. aquatic plant research conf. Governor's Aquatic
Research and Develop. Commit. Gainesville. Feb. 20.

Rushing, W. N. 1975. Marisa and other snail predators of macrophytes.
p. 61-65. In Brezonik, P. L. and J. L. Fox (eds.) Proc. symp. on
water quality management through biological control. Univ. of
Florida and U. S. Environmental Protection Agency, Gainesville,

Jan. 29-31.

Rushing, W. N. 1973. Water hyacinth reaserch in Puerto Rico. U. S.
Army Engineer Waterways Experiment Station. Mobility and Environ-
mental Systems Laboratory. Vicksburg, Miss. Misc. Pap. M-73-13.
32 p.

59


218.

219.

220.

221.

222.

223.

224.

225.

226.

227.

228.

229.

Zolotova, Z. K. 1966. Food preferences of grass carp. (Weed Abstr.
18(6):433, No. 2705) pe

Cross, D. G. 1969. Aquatic weed control using grass carp. J. Fish
Biol. 1(1):27-30. 99 , °

Krupauer, V. 1967. Food selection in 2-year old grass carp. (Weed
Abstr. 18(6):433, No. 2703) $ Pe (

Linchevskaya, M. P. 1969. The diet of grass carp fry. (Weed Abstr.
18(6):433, No. 2706) pay

Korniyenko, G. S$. 1971. The role of infusoria in the food of the
larvae of herbivorous fishes. Vopr Ikhtiol. 11(2):303-310.
(Biol. Abstr. 53:36428; English Translation in J. of Ichthyol.
11(2) 2241-246.)

Sutton, D. L. 1973. Annual report to the Rockefeller Foundation on
the Project: Utilization of aquatic vegetation by the white amur.
Fort Lauderdale Agr. Res. Center, Research Report -- FL 73-5. 14

p.

Stanley, J. G. Energy balance of white amur fed Egeria. Bur. Sport
Fish. Wildlife, Stuttgart, Arkansas. Manuscript. 18 p.

Stanley, J. G. 1972. Utilization of nutrients and effects of grass
carp on eutrophication. Grass Carp. Symp. 102nd Ann. Meeting,
Amer. Fish. Soc. Hot Springs, Ark. 8 p.

Stanley, J. G. 1974. Nitrogen and phosphorus balance of grass carp,
Ctenopharyngodon idella, fed Elodea, Egeria densa. Trans. Amer.
Fish. Soc. 103(3):587-592.

I-Kuei, Chiang, Chang Chin-hsia, and Ch'en Hsi-t'ao. 1973. Nutrition
and bait materials of Ctenopharyngodon idella (Val.). p. H3-H19.
In E. 0. Gangstad, J. J. Raynes and R. M. Burress, et al. Her-
Bivorous fish for aquatic plant control. Aquatic Plant Control
Program, Tech. Rep. 4, U. S$. Army Eng. Waterways Exp. Sta., Vicks-
burg, Miss. (NTIS AD-765 437, Translation)

Blackburn, R. D. and D. L. Sutton. 1971. Growth of the white amur

(Ctenopharyngodon idella Val.) on selected species of aquatic
plants. Proc. Int. Symp. on Aquatic Weeds. Oxford. 3:87-93.

Blackburn, R. D. 1975. Ecology and biocontrol of aquatic weeds in the
Southeast. Florida Agr. Experiment Station. Fort Lauderdale,
Florida. Notice of Research Project, Smithsonian Science Informa-
tion Exchange, Washington, D. C. SIE No. GY-107012-5, GY-107012-6.

65


SECTION 3
RECOMMENDATIONS

Research should continue on all biological control techniques (grazing,
predatory, pathogenic and biomanipulative) as no single method is universally
applicable. Some methods are more promising than others, however.

Grazing by fish has demonstrated little success in controlling algal
blooms. Further research into the grazing potential of other forms, such as
protozoans or zooplankton, may be more profitable. Control of the water
hyacinth by Neochetina and alligator weed by Agasicles and Vogtia has
demonstrated the ability of host-specific insects to control macrophytes.
This type of approach, rather than the indiscriminate introduction of non-
specific fish such as the amur, is recommended as a sounder ecological
practice.

Increased emphasis should be placed on the potential effects of a
control organism on all nontarget segments of the ecosystem into which it is
introduced. Predator or grazer species which are not host-specific and
considered for control of nuisance growths and organisms should be throughly
researched before introduction. These organisms may be better used in areas
where their spread would be restricted by climate. Sterile species should be
a primary consideration in the introduction of nonspecific organisms.

Plant pathogens seem to have much potential for controlling undesirable
species, particularly because of host specificity. Although viral, bacterial,
and fungal controls of algae and macrophytes are wot yet fully usable techni-
ques, they still merit investigation.

Biomanipulative procedures which exploit the interactions between the
biota and their environment appear to be a most promising approach for alle-
viating the symptoms of eutrophication in lakes. These methods avoid for the
most part, the problem of introducing nonspecific or exotic organisms into
the environment. The effectiveness of decreasing algal populations by
increasing zooplankton while reducing zooplanktivores has been demonstrated
and is worthy of further development.

Exploitation of competition between aquatic plants may produce practical
control techniques. Research should continue on the synthesis of naturally
occuring growth inhibiting compounds applicable to algal control. Shifting
predominant algal populations by chemical addition, while more an environmen-
tal than biological manipulation, should also receive further study.

10


Mississippi Silversides--

The Mississippi silversides (Menidia audens) has been proposed as a
control for the standing crop of phytoplankton in Clear Lake, California,
while providing forage for sport fish such as white bass (62). It was also
introduced into Upper and Lower Blue Lakes, California (63). Early results
Were apparently encouraging (64) but it is the opinion of many investigators
that M. audens has had little impact on the algae in the lake system (R.
Brown, pers. comm.).

Mullet--

Prowse (36) suggested that mullet {Muail cephalis) might be used to
control algal blooms in brackish lakes. This fish is important in pisci-
culture in Israel (65) and has sucessfully controlled Cladophora in some
South Carolina duck ponds (58). It has also been stocked in Lake Kinneret,
Israel, for over 12 years to help control algal growth, but results have been
inconclusive (Serruya, cited in 17).

Milkfish--

The milkfish (Chanos chanos) is cultured in brackish ponds in Indonesia,
the Philippines and Taiwan (66, 67) and consumes mainly filamentous blue-
green algae of the Oscillatoriaceae and benthic diatoms (Schuster, cited in
68; 69). A larger milkfish in the Philippines consumes dense mats of floating
filamentous green algae (70). Use of these fish for planktonic algae control
jis not encouraging but they may hold promise in tropical regions with filamen-
tous algae problems.

Others --

Channel catfish (Ictalurus punctatus) can eliminate Pithophora in ponds
when stocked at 2,470 fish/ha (40), but it has not been seriously considered
as a contro] organism. The amur (Ctenopharyngodon idella) has controlled
Pithophora and Hydrodictyon in bluegill pomds (71) but its primary use has
been in controlling vascular plants.

Birds

Swan (Cygnus olor) have been used to control filamentous algae in fish
ponds (Van Deusen, pers. comm.) and are usually stocked at the rate of one
pair per 0.2-0.4 ha of water surface (72). These birds may represent an
acceptable means of control in certain circumstances; however, their con-
tribution to nutrient cycling in addition to amy contribution to nutrient
loading through the utilization of supplemental feed sources should be con-

sidered.

The American flamingo (Phoenicopterus ruber), a native of Guyana which
feeds by straining algae, has been suggested for study; however, it is likely

to be of limited importance (73).

15


Competition has also been considered in fnetuck of eeegstag water-
milfoil (Myriophyllum spicatum) by the lotus (Nelumbo lutea). Shading
effects of the lotus eliminate the milfoil (510); the Totus, in turn, can be
eliminated with about one-twentieth the herbicide required for milfoil (Bates
and Hall, cited in 511).

ALLELOPATHY AND AUTOINHIBITION

Allelopathy, the subject of a recent review by Rice (512), refers to the
growth limiting effects of higher plants upon each other through the release
of retardants into the environment. Current usage also includes the direct
or indirect effects of chemical compounds excreted by micro-organisms. It
has also been used to describe heteroinhibition in algae or the suppressing
action of one species upon another (28). These interactions may prove to be
a major factor in determining the composition of plant communities (508).
Autoinhibition describes the inhibition by an algal species of its own
growth by the secretion of organic compounds (28, 513). The exploitation of
allelopathic and autoinhibitory substances seems a promising area for re-
search on biological control of algae.

Studies in the 1940's resulted in the isolation of a growth-inhibiting
substance, chlorellin, produced by the green alga, Chlorella vulgaris (514,
515, 516). Exceedingly low concentrations of this substance stimulate the
growth of Chlorella cells (517), while higher concentrations inhibit Chlor-
ella and other algal species (518). Later work confirmed that inhibitory
secretions influenced the ecology of blooms (519) and demonstrated that
aquatic macrophytes appear capable of altering phytoplankton populations
(520, 521). These inhibitory substances are important in competition among
tate, psy (522) and are important in the development of the algal flora
512, 523).

Inhibitory substances produced by green algae of the Volvocaceae and
their role in biological control have been studied extensively (513, 524,
525, 526, 527). A substance produced by Pandorina morum has produced en-
couraging results (527, 528). The manner in which these algal inhibitors
operate and their effect upon other organisms are largely unknown; however,
there is hope that they can be synthesized (529).

A heteroinhibitory or allelopathic compound secreted by the bluegreen
alga Anabaena flos-aquae appears to be an important factor in its bloom
formation; it prevents cell division and inhibits the growth of other algae
in the community (530). Compounds of this nature may offer new control
prospects for objectionable blue-greens. However, allelopathy was felt to be
insignificant in maintaining an Aphanizomenon bloom, and autoinhibition was
not a factor in a declining spring bloom of Aphanizomenon in Clear Lake,
California (28).

ENVIRONMENTAL MANIPULATIONS
Shapiro et al. (27; Shapiro, cited in 482) conducted a series of ex-

periments in which predominant algal populations were shifted from blue-
greens to greens by addition of HCl, CO), and Cl). The researchers

44


529.

530.

531.

532.

Harris, D. 0. 1975. Antibiotic production by the green alga, Pandorina
morum. p. 106-111. In Brezonik, P. L. and J. L. Fox feds.
Proc. symp. on water quality management through biological control.
University of Florida and U. S. Environmental Protection Agency.
Gainesville, Jan. 29-31.

Williams, L. R. 1975, Heteroinhibition as a factor in Anabaena flos-
aquae waterbloom production. p. 275-317. In Proceedings:
Biostimulation and nutrient assessment workshop. U. S. Environ-
mental Protection Agency, Ecol. Res. Ser. EPA 660/3-75-034.

Commonwealth Inst. of Biological Control, Bangalore (India). 1969.
Possibilities of biological control of aquatic weeds in India.
Water Resources J., United Nations Econ. Comm. for Asia and the
Far East. p. 40-50. (WRSIC Abstr. W70-06549.

Gangstad, E. 0., P. W. Zimmerman, A. E. Hitchcock, H. Kirkpatrick, T.
T. Earle, T. T. McClure, W. S. Stokes, F. S. Davis, D. P. Schultz,
W. W. Barnes, J. A. Foret, and N. R. Spencer. 1974. Aquatic-use
patterns for 2, 4-D dimethylamine and integrated control. Aquatic
Plant Control Program. Tech. Rep. 7, Army Eng. Waterways Exp.
Sta., Vicksburg, Miss. 140 p.

89


of rotenone and might be stunned by this concentration enabling its transfer
to other water bodies with minimum injury (278).

Advantages as a _control--The advantages of the amur as a biological
control agent are that it is primarily herbivorous and ingests significant
amounts of aquatic weeds, has a rapid growth rate, is edible, has potential
as a sport fish, tolerates a wide range of temperature and water quality, is
susceptible to normally used fish toxicants and is economical as a control
agent (185).

Disadvantages as a control--Disadvantages include: uncertainty of the
effect on native fish; possibility that removal of plants may eliminate
endemic fish food and cover and waterfowl food; lack of knowledge of proper
stocking rates; difficulty of live capture; possibility of natural spawning;
possibility of introducing a disease vector; lack of knowledge of local plant
preferences; and nutrients released into the water by excretion may lead to
increased primary productivity (181, 185,268).

The amur increases the production of other fish species when they are
grown together in commercial ponds (241, 279), the passage of partially
digested food from its gut results in a fertilizing effect which enhances
algal productivity and the subsequent growth of other fish (174). Prowse
(36) reported that the amur elevates the nutrient level of the water to a
point where algal blooms result; Stanley (225) and Mitzner (243) also suggest
this possibility. However, this effect was not noted in some soft water
acidic ponds in Georgia (280).

Since the amur can survive in brackish water (281, 282), there is a
possibility that it could migrate from one river system to another through
estuaries. For this reason the amur might have a profound effect in the
Sacramento - San Joaquin Delta of California should it become established in
that state (270).

The possibilities of disastrous effects upon native invertebrates, fish
and waterfowl following the elimination of aquatic vegetation were emphasized
by Courtney and Robins (282). Other potential hazards mentioned by these
authors include dangers to rice, a threat to the Everglades kite (an endan-
gered bird), and the introduction of an exotic protozoan found in Missouri
known to be carried by the amur. A tapeworm introduced along with the amur
has become a serious problem in Europe (Bardach, cited in 282).

In Britain widespread introduction was discouraged by the government in
1968 in view of possible dangers of disturbing the balance between plants and
native fish (252). Five years later caution was also urged in the United
States by Greenfield (181) who emphasized that the potential danger of the
amur established still exists.

Early concern over the feeding habits of amur and the possibility of

natural spawning led to the Conference of Exotic Fishes and Related Problems
in Washington, D.C., 1968. This group recommended against further releases

27


Biological control programs should also include an evaluation of
the potentially adverse effects of increased nutrient loading from proposed

control organisms such as fish, fowl or mammals, or from procedures such as
fertilization.

More documentation is needed from carefully controlled and properly
designed laboratory and field experiments and full scale projects to fully
evaluate the effectiveness and impact of various control procedures.

More documentation is needed on the economics of biological control
practices.

|


96.

97.

98.

99.

100.

101.

102.

103.

104.

105.

106.

alligator weed management. Aquatic Plant Control Program. Tech.
Rep. 10. Army Eng. Waterways Exp. Sta., Vicksburg, Miss.

Blackburn, R. D. and L. A. Andres. 1968. The snail, the mermaid and

the flea beetle. p. 229-234. In Yearbook of agriculture. U. S.
Dep. Agr.

Maddox, D. M., L. A. Andres, R. D. Hennessey, R. D. Blackburn, and N. R.
Spencer. 1971, Insects to control alligatorweed, an invader of
aquatic ecosystems in the United States. BioScience 21(19):985-

Andres, L. A. and E. 0. Gangstad. 1973. Biological control of alliga-
tor weed with insects. p. C3-C14. In Gangstad, E. 0., S. L.
Solymosy, G. B. Vogt, L. A. Andres, and L. W. Weldon. Biological
control of alligator weed. Aquatic plant control program. Tech.
Rep. 3. Army Eng. Waterways Exp. Sta., Vicksburg, Miss.

Hawkes, R. B. 1965. Domestic phases of program designed to use insects
to suppress alligatorweed. Proc. South. Weed Conf. 18:584-585.

Hawkes, R. B., Lloyd A. Andres, and W. H. Anderson. 1967. Release and
progress of an introduced flea beetle Agasicles n. sp., to control
alligatorweed. J. Econ. Entomol. 60(5):1476-1477.

Zeiger, C. F. 1967. Biological control of alligatorweed with Agasicles
n. sp. in Florida. Hyacinth Control J. 6:31-34.

Maddox, D. M. and R. N. Hambric. 1970. Use of alligatorweed flea
beetle in Texas: An exercise in environmental biology. Proc.
South. Weed Conf. 23:283-286.

Spencer, N. R. and J. R. Coulson. 1975. The biological control of
alligatorweed. p. 36-44. In Brezonik, P. L. and J. L. Fox (eds.)
Proc. symp. on water quality management through biological control.
Univ. of Florida and U. S. Environmental Protection Agency,
Gainesville, Jan. 29-31.

Spencer, N. R. 1973. Insect enemies of aquatic weeds. Presented at
Third International Symp. on Biological Control of Weeds; Sept-
ember. Montpellier, France. 13 p.

Spencer, N. R. 1974. Insect enemies of aquatic weeds. Pest Art. News
Summ. 20(4):444-450.

Weldon, L. W., R. D. Blackburn, and W. C. Durden, Jr. 1973. Evaluation
of the Agasicles n. sp. for biological control of alligator weed.
p. D3-D54. In Gangstad, E. 0., S. C. Solymosy, G. B. Vogt, L. A.
Andres, and L. W. Weldon. Biological control of alligator weed.
Aquatic Plant Control Program. Tech. Rep. 3. Army Eng. Waterways
Exp. Sta., Vicksburg, Miss.

55


ABSTRACT

A total of 532 references on the biological control of aquatic nuisances
were reviewed. Three major control approaches exist. Grazing and predation
have been the most frequently utilized techniques, with emphasis on macro-
phyte control by fish and insects. The use of pathogens is potentially
effective, with most promise in macrophyte control. Biomanipulation, the
exploitation of the interrelationships among plants, animals and their envi-
ronment, is considered a most promising technique for eutrophic systems.
This approach includes increasing algal grazers while controlling zooplankti-
vores and exploiting the competitive and growth-limiting reactions among var-
jous species. The importance of using host-specific organisms to prevent
damage to desirable components of the ecosystem is emphasized.

Work was initiated in September, 1974, and completed January, 1977.

vi


503.

504.

505.

506.

507.

508.

509.

510.

511.

512.
513.

514,

515.

Surber, E. W. 1961. Improving sport fishing by control of aquatic
weeds. U. S. Fish-Wildlife Serv. Circ. 128. 51 p.

Schryer, F. and V. W. Ebert. 1972, Determination of the effects of a
fertilizer induced plankton turbidity supplemented by herbicides on
submerged aquatic plants. Kansas Forestry, Fish and Game Comm. 11
p.

Blackburn, R. D. 1966. Weed control in fish ponds in the United
States FOA Fish. Rep. 44(5):1-17.

Clugston, J. P. 1963. Lake Apopka: A changing lake and its vegetation.
Quart. J. Fla. Acad. Sci. 26:168-174.

Yeo, R. R. 1971. Status of slender spikerush for controlling certain
rooted aquatic weeds. Weed Sci. Soc. Amer. 11:32. (Abstr.)

Frank, P. A. 1975. Competitive interactions among aquatic plants. p.
24-27. In Brezonik, P. L. and J. L. Fox (eds.) Proc. symp. on
water quality management through biological control. Univ. of
florida and U. S. Environmental Protection Agency, Gainesville,
an. 29-31.

Yeo, R. R. and D. A. Frank. 1975, Biological control of aquatic weeds
with plant competitors. Univ. of Calif., U.S.D.A. Agric. Res.
Service, Davis. Notice of Research Project, Smithsonian Science
Information Exchange, Washington, D. C. SIE No. GY-41311.

Tennessee Valley Authority. 1972. Control of Eurasian watermilfoil

(Myriophyllum spicatum L.) in TVA reservoirs (final impact state-
ment). Office of Health and Environmental Science, Rep. TVA-OHES~-

72-8, 88 p. (NTIS EIS-TN-72-3397-F)

Smith, G. E. 1971. Resume of studies and control of Eurasian water-

milfoil (Myriophyllum spicatum L.) in the Tennessee Valley from
1960 through 1969. Hyacinth Control J. 9(1)23-25.

Rice, E. L. 1974. Allelopathy. Academic Press, New York. 353 p.

Harris, D. 0. 1971. Growth inhibitors produced by the green algae
(Volvocaceae). Arch. Mikrobiol. 76:47-50.

Pratt, R. and J. Fong. 1940. Studies on Chlorella vulgaris II. Further
evidence that Chlorella cells form a growth-inhibiting substance.

Amer. J. Bot. 27:437-436.

Pratt, R. 1944. Studies on Chlorella vulgaris IX. Influence on the
growth of Chlorella on continuous removal of chlorellin from the

solution. Amer. J. Bot. 31:418-421.

87


hampered by aquatic weed infestations which impede irrigation, drainage and
navigation (331). It is known to consume 36 genera of macrophytes from
Florida and Guyana (73). Water hyacinth is generally not consumed when other
plants are available (332).

These unique animals, which can attain a length of over 3 m and a
weight of 900 kg (333, 334, 335,), can consume over one-quarter of their body
weight in aquatic plants per day (73). In Guyana, two manatees cleared a
canal 6.7 m wide and 1,463 m long, of aquatic weeds in 17 weeks (336). Five
Florida manatees, total weight 2,268 kg, were estimated capable of clearing a
805 m canal in 3 weeks (Sguros, cited in 96). Various ponds and canals in
Guyana have been kept clear of aquatic weeds for many years (335) and more
than 120 manatees have been introduced into the canals of that country (73).

The use of the manatee is limited because of its susceptibility to
predators, including man, and a lack of knowledge of its reproduction and
physiology (14, 337, 338). If satisfactory husbandry could be achieved
however, this animal could be effective in many tropical areas of the world
(73). It is more effective and longer lasting in certain areas than chemical
controls (336), represents a rapid and economical method of weed control,
(96) and is useful in keeping channels clear (339).

The manatee does not breed in captivity and its slow reproductive rate
is an obstacle to large scale utilization (73, 333). In Panamanian lagoons,
selective feeding did not include the weeds used for breeding by pest insects
(340). Weed control by the manatee was also tried in the Chagres River in
Panama for 3 or 4 years before it was given up as unsuccessful (341).

The need for fundamental research on the reproduction, physiology and
husbandry of the manatee has been urged by many (96, 331, 335, 339). The
establishment of an international center for manatee research, probably in
Guyana, has been recommended by scientists from eight countries. The center
would study basic manatee biology, its effectiveness in weed control, and
ways to promote its conservation and domestication (331, 342).

Domesticated Animals--

Controlled grazing by cattle has been suggested to control vegetation
along lake shores and canal banks (Levett, cited in 14) and to prevent the
spread of the vegetative mat of water hyacinth in Guyana (73). Water hya-
cinths, when accessible, are also eaten by cattle in Australia (343) and the
Nile Valley (344). Common cattails have been controlled by grazing (345).
Control of reeds by cattle can be efficient (327), but it is effective for
only a short time (65). Sheep, goats and horses are less efficient than
cattle in controlling reeds (327).

Water buffalo, suggested as a control for emergent vegetation in Guyana
(73), may be used in an attempt to control water hyacinth near Orlando,
Florida (346), and are being tested for effectiveness near Gainesville,
Florida (347). An attempt to import the hippopotamus into this country for
weed control has been reported; however, the animals would have been unable

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SECTION 5
USE OF PATHOGENS

Plant pathogens may ultimately be one of the most important methods of
controlling aquatic weeds (376). Freeman et al. (377) and Freeman and Zettler
(378) have pointed out that the large number of existing plant diseases make
it likely that a usable pathogen can be isolated; many plant pathogens are
host specifics pathogens are in general, readily disseminated and may not
require reapplication; they would not completely eliminate a plant species;
and they may not be harmful to animal life. Much of the work on plant path-
ogens in this country is now carried out at the University of Florida, Depart-
ment of Plant Pathology. Major emphasis is on identifying and evaluating

diseases of the water hyacinth (Eichhornia crassipes), alligator weed (Al-
ternanthera philoxeroides), hydrilla (Hydrilla verticillata) and Eurasian
watermilfoil (Myriophyllum spicatum) ‘

VIRUSES

Control of Blue-green Algae

Cyanophages, or viruses infecting blue-green algae, were first isolated
in 1963 (379). Many cyanophages have since been discovered (Table 2). A
particular virus is designated by the first letter of the generic names of
the algae it infects. Cyanophages resemble bacteriophages in morphology.
multiplication and composition. They directly affect the photosynthetic
apparatus of the host cell (397). Cyanophages are widely distributed in
fresh water, having been isolated from streams, rivers, ponds, lakes, waste
treatment ponds and industrial storage waters (398, 399, 400).

Jackson and Sladecek (401) reviewed progress in blue-green algal virus
research from 1963-1970. The host range, morphology. chemistry, physical
properties, infection process and ecology were then reviewed by Brown (402).
Safferman (403) emphasized the taxonomy, history, algal control aspects and
interaction of various cyanophages. Padan and Shilo (399) reviewed and
discussed the characteristics, growth cycles, interactions and genetics of
cyanophages. Cannon (404) and Cannon et al. (405) have discussed recent
blue-green algal virus research. Safferman and Morris (406) recently com-
piled a bibliography containing 75 references on cyanophages and 13 references
on virus-like agents infecting algae other than blue-greens.

35