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 AFM 91-19 / TM 5-629 / NAVFAC MO-314
24 May 1989
54
are suitable only for certain warm waters in
and reservoirs; in drains and irrigation canals;
southern states. Adult Tilapia can survive and
on ditch-banks; and in reservoirs and canals
reproduce in fresh or brackish water that does
carrying drinking water. Rates and times of
not fall below 50 F.
application are given in general terms because
b. The Chinese grass carp is adapted to a
local climates, water temperatures, site condi-
wide range of climatic conditions, and it has
tions, and water uses affect the performance and
performed very well as a biological control for
persistence of the herbicides and the procedures
aquatic weeds. Few states now permit the intro-
required for their safe and effective use.
duction of the Chinese grass carp (and then only
c. Specific guidance should be obtained from
the sterile triploid form) because of uncertainty
state or federal aquatic weed specialists who are
regarding its possible detrimental effects on
familiar with these local conditions. The county
native fish and the aquatic environment. In
extension agent and the state fish and wildlife
some of the southern states the Israeli carp is
department are excellent sources of information.
stocked to control filamentous algae.
d. Special precautions must be observed if the
c. Grass carp are normally stocked at a rate
water is to be subsequently treated and used for
of 10 to 20 fish per acre. They eat submerged
human consumption. Normally, the chemical of
plants, but, if there is an inadequate supply of
choice in or near potable water is copper sulfate,
their preferred food, they will even feed on lily,
fosamine, or AMS. Other compounds should be
cattail, and other emergent species. Do not stock
used only with prior approval of a MAJCOM or
them where aquatic plants are desired, and use a
EFD pest management consultant.
conservative stocking rate regardless of the se-
verity of the weed problem.
7-13. Safety Considerations:
d. These fish could be harmful in wetland
a. A few aquatic herbicides, such as acrolein,
areas and waterfowl habitat. Be sure to comply
are poisonous to humans and other warm-
with state and federal regulations.
blooded animals, and must be handled and used
with caution and according to special proce-
dures. Some herbicides are toxic to fish, but
7-11. Other Biological Control Agents. The
most do not injure fish at the concentrations
Agasicles beetle and stemborer, introduced to
required for weed control. Some injure fish food
the United States from South America, are
organisms, and a few may injure crops at low
currently providing excellent control of Alliga-
concentrations if they are used carefully.
torweed throughout much of this weed's range.
b. Only limited information is available on
Other biological control agents, such as plant
the persistence and fate of herbicides in water,
pathogens and competitive vegetation, are under
in aquatic soil, in fish, and in aquatic plants.
study.
Judgments on herbicide residues are subject to
continual change on the basis of new informa-
Section F -- Using Herbicides
tion on the persistence of residues, toxicity to
fish, etc. Labels on herbicide packages are kept
up-to-date on such changes. Therefore, in addi-
7-12. Recommended Herbicides:
tion to following all the precautions in chapter 1
a. Herbicides often give more effective, longer
for safely using herbicides, the user of an
lasting, and less expensive control of aquatic
aquatic herbicide must determine that the treat-
weeds than do mechanical or hand methods. In
ment is necessary, and must carefully follow all
some ways, however, using herbicides to control
instructions and restrictions on the label regard-
aquatic weeds is more difficult and perhaps
ing aquatic situations in which the herbicide
more hazardous than their terrestrial use. cop-
should and should not be used. The user must
per sulfate was first used to control algae in
know how much time should elapse after herbi-
1904, and sodium arsenite was used to control
cide treatment before treated water is used for
waterhyacinth in 1902 and submersed weeds in
drinking, fishing, swimming, or irrigating crops-
1927. However, most of the herbicides now
c. Local water quality regulations also must
registered by the Environmental Protection
be considered. Herbicides should not be used in
Agency for use in controlling one or more
or near marshes and other wetland habitats
aquatic weeds were discovered since 1945.
unless their use has been clearly determined to
b. Attachments 26 through 29 show herbicides
be necessary.
that are recommended for use in ponds, lakes,
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