Chemical Treatment
Herbicides & Algaecides
Chemical treatment is one of the oldest methods used to
manage nuisance aquatic weeds, and is still the most
frequently applied approach.
There are few aspects of plant control that breed more
controversy than chemical control through the use of
herbicides, which are a subset of all chemicals known as
pesticides. Part of the problem stems from pesticides that
have come on the market, enjoyed widespread use, been
linked to environmental or human health problems, and
been banned from further use. Some left long-term
environmental contamination and toxicity problems behind.
Advantages
 Wide
range of control is possible
 May be able to selectively eliminate
species
 May achieve some algae control as well
 May allow for more desirable plant growth
Disadvantages
 Possible
toxicity to non-target species
 Possible downstream impacts
 Restrictions of water use for varying time
after treatment
 Increased oxygen demand from decaying
vegetation
 Possible recycling of nutrients to allow
other growths
Information for Proper Application

Mapping of area to be covered by barrier, with
information on plant types and density
 Knowledge of sediment features, along with any
obstructions or other interference factors
 Inventory of biological features of the target
area, especially the presence of any protected
species
 Plan for installation and maintenance
Types of Herbicides

Contact herbicides - toxic to plants by uptake
in the immediate vicinity of external contact.
More effective against annuals than perennials
because they may not kill the roots, allowing
perennials to grow back.
 Systemic herbicides - taken up by the plant
and are translocated throughout the plant.
Generally provide more effective control of
perennial plants than contact herbicides, as they
kill the entire plant under favorable application
circumstances.
Types of Herbicides

There are a number of aquatic herbicides on the
market.
 Aquatic herbicides must be registered by the
EPA and the Massachusetts Department of
Agricultural Resources for legal use in
Massachusetts. The criteria addressed in the
registration process include data on forms of
toxicity, impacts to non-target organisms,
environmental persistence, breakdown products
and fate of the herbicide constituents in the
aquatic environment.
Restrictions following Application
 Depending
on chemical application it may
be prudent to avoid swimming for a short
period of time.
 Irrigation restrictions of several days or
more are common
 Copper and fluridone products are used in
human drinking water supplies.
Considerations For Application




What is the acreage and volume of the area(s) to be
treated? Proper dosage is based upon this information.
What plant species are to be controlled? This will
determine the herbicide and dose to be used.
How is this water body used? Many herbicides have
restrictions of a day or up to two weeks on water use
following application, and most cannot be used in
drinking water supplies.
What will the long-term costs of this decision be? Most
herbicides must be reapplied annually, with a range of
two or three times per growing season to once per five
years possible.
Concerns to Consider
 Impacts
to non-target flora centers on
protected species and overall impacts to the
plant community that may affect habitat for
fish and wildlife. Some level of temporary
impact to non-target flora is almost
unavoidable with herbicide use, but recovery
of plant communities is often rapid.
 Potential for direct toxic effects on non-target
fauna.
Permitting
 Notice
of Intent required.
 In 2007 Chemical Application at Little
Hickory permitting/recording costs


Permit Fees $956.84
Recording Fees $75.00
Chemical Applications
at Little Hickory

Summer of 2001 area treated with fluridone
herbicide to control nuisance vegetation;
dominant plants were largeleaf pondweed and
watersheild.
 Survey done 9/27/05 revealed that since 2001
there had been a gradual increase in density of
watershield and a more aggressive increase in
pondweed. Several instances of ribbonleaf
pondweed were also noted.
Chemicals applied in 2006
 Fluridone
 Rodeo
(Sonar)
(glyphosate) approval for small
applications in Pond during future years of
program (3 year program)
Chemical Application Cost 2006
 $3,625.00



Total
Filing Fees
Application
Recording Fees
$ 956.84
$2591.86
$ 76.30
($2000 funded by HHL, remainder funded by
Little Hickory Residents)
Lake Shirley treated chemically last year for
the 1st time, total cost of approx. $70,000.
Current Recommendations of
Aquatic


“Several USEPA / State registered herbicides are
available for control of the plants present in Hickory Hills
Lake. Herbicide selection would be based on the target
plants and impacts on non-target species are generally
minimal. Herbicide treatment poses a negligible risk to
the environment when conducted by licensed applicators
in accordance with the product label.”
“We expect that herbicide treatment could be used to
augment the harvesting program, in specific high-use
areas of the lake, if so desired by the Association.”
Costs Quoted by Aquatic in 2008
Survey for Chemical Application
 “Permits
would need to be filed with the
Lunenburg Conservation Commission at a
cost ranging from $2,500-$4,000
 “Treatment costs generally range from
$400-$800 per acre depending on the
herbicide used.”
Sources

2004 Practical Guide to Lake Management in
Massachusetts, Executive Office of
Environmental Affairs
 Aquatic Control Technologies
http://www.aquaticcontroltech.com/physical_treat
ments.html & 2008 Hickory Hills Survey
 Hickory Hills Notice of Intent (on File with
Lunenburg Conservation)
 Lycott Environmental
http://www.lycott.com/benthic_screening.html