AUSTIN – Texas Parks and Wildlife Department (TPWD) inland fisheries staff found a total of 30 acres of invasive giant salvinia in multiple locations at Lake Nacogdoches Feb. 5.

Within days of the discovery of a half-acre of giant salvinia at the Yellow Bank Creek cove, the TPWD Brookeland aquatic habitat enhancement team (AHE) deployed to the reservoir and found a larger infestation where Little Bayou Loco enters the reservoir. Those areas will be treated with a combination of giant salvinia weevils and careful application of contact herbicide on larger mats of the invasive plant.

“We will use weevils in the areas where the giant salvinia is being contained by other vegetation and only treat mats of salvinia when they form,” said Brookeland AHE team lead John Findeisen. “The containment vegetation – mainly consisting of cutgrass and torpedo grass – is crucial to the success of managing the giant salvinia at Lake Nacogdoches.”

Findeisen said herbicidal treatment on the areas where giant salvinia is being contained by other vegetation can exacerbate the problem. The containment vegetation, which prevents the invasive plant from rapidly spreading throughout the lake, can also block the herbicide from landing on its intended target. Eliminating the containment vegetation can also negatively impact fish and wildlife by removing available natural habitat. In these cases, giant salvinia weevils are the only option.

It’s likely the giant salvinia traveled to Lake Nacogdoches by way of a visiting watercraft in the summer of 2017, Findeisen added. Similar to the most recent infestation at Lake Fork, staff believe there is enough giant salvinia scattered throughout the lake that eradication would be almost impossible at this point.

“We will be treating the larger mats of giant salvinia to manage the infestation the best we can,” Findeisen said. “But we still need boaters, anglers and duck hunters to do their part and be diligent about cleaning, draining and drying their equipment when traveling from lake to lake – especially in East Texas where invasive species like giant salvinia thrive.”

Giant salvinia has been present in Texas for nearly 20 years. Giant salvinia was first discovered on Toledo Bend in 1998 and has since spread throughout East Texas. In addition to current infestations at Toledo Bend, Sam Rayburn and Caddo Lake, the invasive plant has been newly introduced or reintroduced at five Texas lakes since 2017: Lake O’ the Pines, Lake Palestine, Martin Creek Lake, Lake Fork and now Nacogdoches Lake.

All boaters should learn to identify giant salvinia as well as other invasive species that occur in Texas waters. Most importantly, boaters should remember to clean their boats and trailers before leaving the boat ramp. Transporting giant salvinia, along with other invasive species, is prohibited by law and punishable by a fine of up to $500 per violation.

Boaters and property owners are urged to clean, drain, and dry their boats and trailers in between trips and to report additional infestations outside of the affected areas by calling (409) 698-9121 or emailing AquaticInvasives@tpwd.texas.gov.

For more information on giant salvinia and other invasive species, visit tpwd.texas.gov/giantsalvinia.