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$ Permit Fees$ Recording Fees $75.00 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 (Sonar)  Rodeo (glyphosate) approval for small applications in Pond during future years of program (3 year program)

Chemical Application Cost 2006  $3, Total Filing Fees$ Filing Fees$ Application$ Application$ Recording Fees$ ($2000 funded by HHL, remainder funded by Little Hickory Residents) Lake Shirley treated chemically last year for the 1 st time, total cost of approx. $70,000. Recording Fees$ ($2000 funded by HHL, remainder funded by Little Hickory Residents) Lake Shirley treated chemically last year for the 1 st 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 tments.html & 2008 Hickory Hills Survey tments.html tments.html  Hickory Hills Notice of Intent (on File with Lunenburg Conservation)  Lycott Environmental