Written by Industry Expert Eric Carnall, Environmental Scientist
Alligatorweed (Alternanthera philoxeroides) is a perennial plant native to South America. It was first reported in the United States in 1897. Listed as a prohibited aquatic weed in many states, its growth has caused significant economic and ecological damage throughout the Southern United States.
Alligatorweed reproduces in North America primarily through vegetative propagation, but seeds have been found as well. Morphologically speaking, alligatorweed can be varied based on the surrounding environment; in fact, it has adapted to grow in both aquatic ecosystems and xeric (desert) habitats. Typically, this invasive plant can be identified by its elliptical or lanceolate leaves with smooth margins arranged in opposite pairs along the shoots. The shoots form roots at the nodes along a hollow stem, which keeps the shoots buoyed in the water—thus forming dense, floating mats. Alligatorweed also forms white flower clusters on a spike which protrudes from the leaf axial.
The unimpeded spread of alligatorweed in non-native environments can lead to serious problems. Due to its rapid growth rate, the invasive weed can quickly inhibit or block the drainage of water from canals and ditches, leading to flooding and increased sedimentation. It displaces native plants along banks and in shallow water, which also eliminates food sources for native animals and can reduce dissolved oxygen exchange, further diminishing native vegetation.
Alligatorweed not only disrupts the balance of aquatic ecosystems, but it can also severely limit recreational activity in lakes and ponds. Fishing and swimming may be negatively impacted by dense mats of growth that can block boat navigation. These mats also provide increased habitat for mosquitoes, which are an unwelcome addition to an otherwise enjoyable outing on the lake. Additionally, the aesthetics of community and golf course ponds are diminished with the presence of alligatorweed, potentially affecting their economic outlook.
The effective control and management of alligatorweed can be achieved through both biological and mechanical means. The release of the Alligatorweed Flea Beetle in North America is one example of a biological control method, though, to date, it has produced minimal results primarily due to its low concentrations and life cycle. Thrips, moths, and stem borers are also being evaluated for use in the control of the invasive plant species.
If biological means prove unsuccessful, hydro-raking is a common and effective alternate solution. A hydro-rake, which is essentially a floating backhoe with a mounted rake attachment, can collect more than 500 pounds of the plant biomass and associated root structure in each scoop and deposit it onshore for proper disposal. Because a hydro-rake works from within the water, it does not impact delicate shorelines.
For particularly large alligatorweed infestations, hydro-raking can be combined with the application of EPA-registered herbicides. Due to its hollow stems and easy fragmentation, herbicides are recommended to reduce the initial biomass prior to mechanical removal to help prevent additional vegetative propagation. Once management has been achieved, close monitoring of the banks should be maintained to thwart any regrowth of the plant.
Ultimately, when it comes to nuisance and invasive species, prevention is key. In most cases, prevention through proactive management is safer for the environment and more cost-effective for communities, municipalities, golf courses and private landowners. Contact your lake management professional to learn more about invasive species management and prevention.
Contact the experts at 888-480-LAKE (5253) for all of your lake, pond, wetland and fisheries management needs.
Eric Carnall is an Environmental Scientist with more than a decade of experience developing sustainable solutions for aquatic ecosystems suffering from nuisance aquatic weeds and algae throughout central Florida and surrounding regions. Eric is a licensed Aquatic Applicator and has a Bachelor of Science degree in Environmental Science from the University of Florida. He has helped lead a variety of notable projects and maintains a Florida Master Naturalist Certification, making him a valuable source of environmental knowledge for clients and peers.
SOLitude Lake Management is a nationwide environmental firm committed to providing sustainable solutions that improve water quality, enhance beauty, preserve natural resources and reduce our environmental footprint. SOLitude’s team of aquatic resource management professionals specializes in the development and execution of customized lake, stormwater pond, wetland and fisheries management programs that include water quality testing and restoration, nutrient remediation, algae and aquatic weed control, installation and maintenance of fountains and aeration systems, bathymetry, mechanical harvesting and hydro-raking, lake vegetation studies, biological assessments, habitat evaluations, and invasive species management. Services and educational resources are available to clients nationwide, including homeowners associations, multi-family and apartment communities, golf courses, commercial developments, ranches, private landowners, reservoirs, recreational and public lakes, municipalities, drinking water authorities, parks, and state and federal agencies. SOLitude Lake Management is a proud member of the Rentokil Steritech family of companies in North America. Learn more about services and purchase products at www.solitudelakemanagement.com.