are being implemented, there`may be no other option than the use of
or herbicidal chemicals.
The chemical and physical properties of herbicides are described by
including a list of manufacturers who will provide
on
application, dose, target species, and user precautions.
A handbook entitled
Their Identification and Methods of Control" has been
"Aquatic Weeds:
lished by the Illinois Department
Conservation, Springfield, IL.
This and
similar reports prepared by other states can be useful
calculating doses
and in determining the identity of nuisance plants.
Reservoir managers should
be aware that a commercial applicator's license, along with liability insur-
ance, is required when the work is contracted. Prospective users of these
..
chemicals should consult the appropriate state regulatory agency to obtain a
list of approved chemicals for that state.
Assistance in determining which
chemicals are approved for use cannot be obtained from the Office of Pesticide
Programs of the US Environmental Protection Agency at this time.
Effectiveness and Feasibility
The following paragraphs briefly review the most commonly used chemicals
with regard to effectiveness, persistence, toxicity to nontarget organisms,
and
factors.
Copper-containing compounds
Copper has been used as an algicide throughout this century to produce
short-term relief from nuisance algal blooms.
More recently, chelated copper
compounds have been used to keep the copper concentration in the water column
high for longer periods.
Usually a dose of 1 to 2 ppm (0.8 mg Cu
pro-
vides significant algal control, apparently through inhibition of photo-
synthesis and nitrogen fixation, for a period ranging up to 10 days.
Unless nutrient input and water column nutrient concentration of a
eutrophic reservoir are significantly reduced, or zooplankton grazing on algae
sharply enhanced, problems with nuisance algal blooms will likely continue.
The use of copper or other algicides such as simazine may be the only feasible
occur.
choice for control of an algal bloom if nutrient reduction does nor
The use of copper results in several significant environmental impacts.
A massive algal kill, such as
occur if too great an area is treated per
day, may produce a large decline in
dissolved oxygen as the cells
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