Great Lakes Hydrilla Collaborative
Recommendations for Prevention, Detection, and Response

Prevention

Prevention

The first step to prevent the spread of hydrilla is public education directed toward water users, including passive recreation users, boaters, and fishermen. It is important to share information about the potential impacts of hydrilla, and what can be done to reduce the risks associated with the transport of hydrilla.


 
Number 1

Develop a public information campaign to educate the public, specifically recreational water users, on what is hydrilla, how to identify it, and the threat it poses to the Great Lakes.

This recommendation focuses on public education through development of hydrilla-specific targeted outreach and educational materials, drawing upon existing regional and national program materials, and using existing venues to distribute the materials. Examples include distributing materials at public and private marinas and botanical gardens, organizing lake management and angler association membership mailings and events, developing state aquatic nuisance species programs, and conducting workshops implemented by Partnerships for Regional Invasive Species Management (PRISMs).

Outreach and educational materials should include the following content to be most effective:

Education
Hydrilla plant, Tonawanda Creek.
  • Information on how to identify the plant and how to distinguish it from native plants. The Hydrilla Hunt! ID sheet and ID card are examples of identification materials.
  • An overview of hydrilla’s potential impacts if it successfully establishes in the Great Lakes and the importance of diligence with respect to early detection efforts.


 
number 2

Post signage at all access points and implement watercraft inspections at areas of high traffic or at highest use boat ramps within priority public watercourses.

Signage, watercraft inspections, wash stations, and nuisance species disposal stations should be provided with priority given to already infested waters, waters with high boater activity, and waters in proximity to existing infestations. These activities are the most critical in the five high risk Great Lakes watersheds (Southeastern Lake Ontario, St. Clair-Detroit, Western Lake Erie, Southern Lake Erie, and Southwestern Lake Erie). Inspection consists of visually inspecting all areas of boating and recreational equipment (e.g., boats, trailers, motors, livewells, anchors, snorkeling and scuba gear, and paddles) that come into contact with or hold water; removing visible plants, animals and mud; and draining water from all compartments/containers.

An example of an aquatic invasive species (AIS) watercraft education program is the Clean Boats Crew: Guidelines for the Illinois and Indiana Aquatic Invasive Species Volunteer Outreach Program. The manual for this program provides information on how volunteers can organize an AIS watercraft education program, including how to conduct an inspection and a sample script for how to approach recreational users.


 
number 2

For coastal wetland restoration projects within the littoral zones of the Great Lakes, include specific requirements for post-construction monitoring of invasive species, including hydrilla, in project plans and specifications.

Some Great Lakes states, such as Ohio, are focused on coastal wetland restoration to improve water quality by reducing nutrient and sediment loading to Lake Erie and incorporating beneficial use of dredge material to enhance coastal wetland and fisheries habitat. Projects that incorporate fill material should confirm the absence of hydrilla and other AIS from source areas prior to selecting and using fill for aquatic habitat restoration. Additionally, these projects should include specific requirements for post-construction monitoring of AIS, including hydrilla, in all project plans and specifications.


Detection

Detection

New Populations

 
Detection

Visual monitoring should prioritize boat ramps/launches and inlets in waterbodies without existing infestations, popular recreational waterbodies and embayment’s with marinas, and waters with depths less than 25 feet.

Inland waterbodies are expected to be more vulnerable to a hydrilla infestation than the Great Lakes proper because they are less turbulent, shallower, and warmer. However, early detection efforts should include nearshore, littoral zone habitats of the Great Lakes watersheds at the highest risk (Southeastern Lake Ontario, St. Clair-Detroit, Western Lake Erie, Southern Lake Erie, and Southwestern Lake Erie).


 
Detection

Develop a specific process for people to report sightings/presence of hydrilla, including agency verification.

For example, EDDMapS provides real-time tracking of invasive species locations and an online tool to report sightings.


 
 

Areas with Current Infestations


 
Detection
Education

Focus monitoring efforts near existing infestations, using a bathymetric map or transects prioritized by likely invasion points or potentially threatened resources.

Use of a bathymetric map of the site can help hone in on areas where water depths are suitable for hydrilla (i.e., 25 feet or less), and transects can be established in those areas at regular intervals. If resources are limited, transects should be prioritized based on likely invasion points (access points) or potentially threatened resources (e.g., intakes, swimming areas, and key habitat).


Detection

Response

Rapid Response

 
Detection

Focus response efforts on use of a contact herbicide.

Contact herbicides control hydrilla relatively quickly by damaging the part of the plant that comes in direct contact with the herbicide.


 
Detection

Advocate that state agencies develop a streamlined process that facilitates rapid response upon detection.

Successful rapid response will require close coordination with regulatory agencies and a willingness on the part of regulators to streamline permitting processes, where feasible. Laws and permitting, specifically with respect to application of herbicides, need to provide a path to rapid treatment of new infestations. Existing permitting processes in many states have review and public notification timeframes that hamper the ability to treat hydrilla quickly. Thus, there is a need for a streamlined permitting process. Such a “rapid response” permit should be considered by state agencies for treatments of areas under 3 acres to provide leeway for managers to quickly address new infestations.

Long-term Sustained Control

Eradication is a multi-year effort and requires a long-term commitment. Since successful eradication programs often require more than five years of treatment, it is important to obtain support from agencies and project proponents, as well as a sustained funding source.

Detection

Herbicide application is the most effective means of hydrilla management in the Great Lakes. Grass carp, which have been implemented at a much lower frequency in small water bodies, are used in concert with herbicides to manage lower-level infestations. The U.S. Army Engineer Research and Development Center is currently researching potential biocontrol agents for monoecious hydrilla, but no such agents are currently available. Mechanical controls are not a preferred management option unless the infestation is limited to a small patch of hydrilla that can be isolated with a curtain. Mechanical controls can be costly, labor-intensive, and result in extensive spread of plant fragments.

Hydrilla can be found in a variety of systems, from lakes and reservoirs to flowing streams. Identification of the most effective treatment plan for each site is a case-by-case exercise. The following is general guidance:

Detection

Refer to the Case Studies page for examples of management in various systems.


 

Control of Isolated Hydrilla Patches

With effective, long-term, sustained control, hydrilla can transition to isolated patches/satellite populations that survive treatment or re-sprout from the bank of subsurface tubers. For these isolated patches, several approaches have been documented to be effective and are recommended:


 
Detection

Apply contact herbicides at the maximum label rates, along with limited public access in those areas.


 
Detection

Use benthic mats (i.e., burlap barriers) on very small patches of hydrilla in shallow, low-velocity water.


 
Detection

Use limnocorrals (impermeable enclosures) to isolate hydrilla beds for direct application of herbicide.