Cornell Cooperative Extension

Tompkins County
Closed sign for herbicide treatment of hydrilla

An area is closed for 24 hours after initial endothall treatment

Hydrilla infestation in Cayuga Lake, photo taken from the Ithaca Farmers' Market side at Johnson's Boatyard toward Cornell, August 10, 2011

Small fragments of hydrilla can "hitchike" on boats to new locations and re-root.

Allied biological, hydrilla treatment

Allied Biological provides herbicide application for the Cayuga Lake Watershed's fight against hydrilla.

Management Options

Options for Controlling Aquatic Plants

The 4 Main Control Mechanisms:

  • Biological: reduce the growth of the plants by introducing predator species such as fish or insects
  • Chemical: applying herbicides that will kill or stunt the growth of the weeds
  • Mechanical: removing the plant (and/or roots) by cutting/dredging or harvesting
  • Physical: disturbing the plants ability to grow by altering the light, soil, or water conditions

Management Plans

A management plan includes the plant management goals and objectives, the control methods to be used and other management strategies such as education to prevent the spread . It takes into account many factors such as the current and future uses of the water body, the priorities of stakeholders, and the resources available (money, expertise, regulations, etc.). As an example, the Cayuga Lake Watershed Hydrilla Management Plan aims for complete eradication.

Some hydrilla management plans have aimed at complete eradication of hydrilla and have succeeded (Successful Eradication in the US), while others have settled on containing the existing population. Areas with well-established infestations have lost the opportunity to completely get rid of the weeds (as seen on theInvasion Curve). Those communities are limited to control methods that regain some form of use during the boating/recreation season. Often they use mechanical or physical controls every year and chemicals every few years.

For a summary of all options, click here.

Last updated January 6, 2020

Management Options

Terminology

In common parlance, the terms 'aquatic plant control' and 'aquatic plant management' are often used interchangeably. When used in a technical way, controls are the techniques or methods used to reduce plant biomass. 

Management can include strategies beyond control efforts such as education to prevent the spread or reintroduction of an invasive plant, like hydrilla. 

This broader category of management strategies is more effective at reaching aquatic plant management objectives, which can range from containing a plant species so that it does not spread further, to temporary or incomplete eradication, to complete and permanent removal of the plant and any reproductive structures.

Resource: Biology and Control of Aquatic Plants, Appendix E: A Manager's Definition of Aquatic Plant Control

Prevention is Key!

Control alone cannot eliminate the threat of hydrilla. Control practices are used for eliminating the existing populations. Prevention is necessary to avoid future invasions and to stop the spread of hydrilla to new locations. Given that small fragments of hydrilla can "hitchhike" on boats and other equipment to new locations and re-root, prevention is very important. Find out more on how you can help prevent the spread of hydrilla!