Control Options

Depending on the plant species there are generally four control methods available: chemical, biological, lake draw-down and mechanical.  A detailed discussion of each of these approaches will be provided in the near future, however, here is brief description to familiarize you with each method.

  • Chemical – Although chemical treatments are very effective in controlling a variety of invasive weeds it can be very expensive.  Only EPA approved chemicals are used that are eco-friendly.  It’s not uncommon for treatments to range for $600 to $1,200 an acre depending on the aquatic plant.  Where milfoil and spiny naiad may need two treatments over the summer season, hydrilla may require five, or more, treatments per year, and continued for several years to bring it under control. Application must be made by a licensed applicator.
  • Biological Control – Sterile triploid grass carp are an effective control for hydrilla and other aquatic plants and typically live for up to 10 years.  Triploid grass carp must be used in a closely managed manner for desirable effectiveness with few, if any drawbacks.
  • Lake Level Drawdown – Milfoil can sometimes be effectively controlled when lake levels are drawn down. The effectiveness of control is determined by several factors including the depth of the drawdown, duration of exposure, presence of springs, and the weather during drawdown.  The success or failure of drawdowns in controlling milfoil on WBL can be highly variable from year to year.
  • Mechanical Control –Mechanical harvesting on Watts Bar Lake is available through one company, Sebastian & Sons Aquatic Weed Removal Inc.

    Mechanical harvesting has advantages and disadvantages discussed under “Weeds” then “Mechanical Harvesting.”

    Benthic barrier mats are another Mechanical Control, but they have proven to be marginally effective. They are hard to keep in place and alter the eco-system they cover.  They are useful in limited areas but are quite expensive to purchase and install.

Laws and Regulations for Treating Aquatic Weeds with Pesticides


The control of invasive aquatic weeds with the use of a restricted use pesticide is regulated by Tennessee laws.

A restricted use pesticide requires handling with special care because it presents a hazard to the applicator and other persons or the environment or because it is toxic to wildlife. The State of Tennessee permits restricted-use pesticides to be applied only by a trained, certified pesticide applicator.

A general use pesticide when used according to directions will generally not cause unreasonable adverse effects to humans or the environment; it does not require special certification for use. Important: Read a pesticide label carefully because it is considered a binding legal agreement between the Environmental Protection Agency and the user.

In Tennessee waterways, only certified pesticide applicators are permitted to threat aquatic plants with restricted use pesticides. Thus, a Watts Bar landowner who wants to have hydrilla, watermilfoil or naiad treated with herbicide is required by law to use a certified applicator. The certification type required in Tennessee for restricted use application is (C05) Aquatic Pest Control.

“Any person who buys, sells, or uses a restricted use pesticide must be licensed by the Tennessee Department of Agriculture as a commercial pest control operator, certified by the department as a certified applicator, or acting under the direct supervision of a license or certificate holder.” Tennessee Department of Agriculture

To find out more about regulations governing restrictive use pesticides on aquatic invasive species or the process to obtain applicator certification, contact one of the following: