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Invasive Hydrilla Plant Confirmed in Robert S. Kerr Reservoir


Invasive hydrilla, an aquatic weed, has been confirmed for the first time in Robert S. Kerr Reservoir in far eastern Oklahoma, according to the Oklahoma Department of Wildlife Conservation. This aquatic nuisance species (ANS) was confirmed by ODWC fisheries biologists after being reported by a citizen.

hydrilla in murray
Priscilla Crawford/iNaturalist (CC-BY-NC)
A clump of invasive hydrilla in Lake Murray.

Hydrilla is considered one of the worst aquatic weeds in the United States.

"Once hydrilla has made its way into a body of water, it will very likely persist as it is incredibly hardy and will further spread the more it is fragmented, said Fisheries Biologist Elaine Gainer, aquatic nuisance species coordinator for the wildlife department.

Hydrilla, native to parts of Asia, Africa, and Australia, was first introduced to the U.S. in the 1950s as a live plant used in the aquarium trade. Hydrilla was first found in Oklahoma in 2006. Now, hydrilla has been found in nearly 40 states.It is a submerged, rooted perennial with long stems (up to 30 feet) that branch at the surface and form dense mats. Small white flowers grow above the waterline on stalks. The stems are covered in small, pointed, often serrated (“saw-toothed edge”) leaves, which are bright green and measure 5/8 of an inch long.

Hydrilla is named after Hydra, the nine‐headed serpent of Greek mythology, because it can grow an entirely new plant from a tiny stem fragment.

hydrilla closeup
thehaplesshiker/iNaturalist (CC-BY-NC)
A closeup of a hydrilla stem, which can grow up to 30 feet long.

ODWC’s Aquatic Nuisance Species program has confirmed invasive hydrilla in Lake Murray, Lake of the Arbuckles, Sooner Lake, Lake Nanih Waiya, Ardmore City Lake, Scott King Lake, and the Lower Mountain Fork River

In just a few years from first arriving in a waterbody, ANS can significantly infest the ecosystem. Preventative actions taken by boaters and other people using infested waters is vital to slow or stop the spread of invasive nonnative species like hydrilla. Using the “Clean, Drain, Dry” procedure is highly encouraged. 

To fight ANS, please remember to drain bilge water, live wells, bait buckets, and boat motors; inspect boats and trailers when leaving the water; scrape off any mussels or aquatic vegetation found when on dry land; then wash and dry off the boat, trailer and accessories. Also, boats allowed to dry for at least a week after contacting infested water are considered safe to take to a different waterbody. For more information on “Clean, Drain, Dry,” go to or

Gainer said invasive species of any kind — plant or animal — should never be returned to the water, and any sightings suspecting ANS should be reported to ODWC by submitting a form online at or by calling 918-200-4815. Anyone reporting a suspected invasive species should take photos to help experts with species identification. 

To learn more about various invasive species affecting Oklahoma, go to


(Top photo: Hydrilla in Lake Murray by Priscilla Crawford/ iNaturalist CC-BY-NC)
(Bottom photo: Hydrilla close-up by thehaplesshiker/ iNaturalist CC-BY-NC)