PHILLIPS, WI (OnFocus) – Curly-leaf pondweed (Potamogeton crispus), an invasive aquatic perennial, has become a notable concern in several Wisconsin lakes and rivers. Originally native to Eurasia, Africa, and Australia, this plant was inadvertently introduced to U.S. waters in the mid-1880s by aquarium hobbyists. Today, its presence poses both challenges and opportunities for aquatic ecosystems and water management in the region.
Characteristics of Curly-Leaf Pondweed
Curly-leaf pondweed is distinguished by its reddish-green, oblong leaves, which are about 3 inches long with distinct wavy, finely toothed edges. The plant’s flat, reddish-brown stem can grow up to 3 feet long. This submersed aquatic plant typically drops to the lake bottom by early July, following its reproductive cycle.
The plant reproduces primarily through turions—vegetative propagules formed in late spring and early summer. After turion formation, the plant dies back, and the turions remain dormant through the summer and early fall. When water temperatures cool, turions begin to germinate, with most sprouting the following spring when temperatures reach about 50°F (10°C).
Spread and Impact in Wisconsin
Curly-leaf pondweed was first confirmed in North America in the 1840s and rapidly spread through the Northeast and Great Lakes regions by the early 1900s. In Wisconsin, it has been identified in numerous water bodies, causing various ecological and recreational issues. An overview map indicates the presence of curly-leaf pondweed, highlighting restricted counties (marked in orange).
One of the significant challenges posed by curly-leaf pondweed is its ability to form dense mats, which can impede activities such as fishing, boating, and swimming. The plant’s midsummer die-off releases phosphorus into the water, potentially causing algae blooms. These blooms can deplete oxygen levels as they decompose, leading to what is known as a dissolved oxygen crash. However, the extent of these impacts varies depending on the lake’s specific characteristics, such as its watershed, nutrient composition, and depth.
Despite these issues, curly-leaf pondweed can also offer some ecological benefits, particularly in highly degraded or turbid environments where other plants may not thrive. It can provide essential services such as food, habitat, and spawning substrates for native wildlife.
Management and Prevention Strategies
Prevention: The most effective strategy for managing curly-leaf pondweed is to prevent its establishment. Wisconsin’s invasive species law prohibits the transport of aquatic plants, live animals, and water from water bodies, with some exceptions for bait. Boaters and anglers are required to inspect and remove aquatic plants and animals from their equipment, drain all water from their boats, and either spray their equipment with high-pressure hot water or let it dry for at least five days before entering another water body.
Mechanical Control: Mechanical harvesting can help mitigate the plant’s impact on recreational activities for a single season by removing plant biomass from the water. However, this method does not eradicate curly-leaf pondweed and can potentially harm non-target native plants and aquatic organisms.
Chemical Control: Chemical treatments, primarily using the herbicide endothall, require multiple years of early-season applications to reduce the turion bank. While this approach can be costly and has not been entirely successful in long-term control, early spring applications when plant biomass is low can help minimize nutrient release. An approved Chapter NR 107 permit is necessary for using herbicides in Wisconsin water bodies.
Small-scale chemical treatments are generally ineffective for curly-leaf pondweed due to the quick dissipation of endothall away from targeted areas. The manufacturer recommends treatments covering more than 5 acres for effective control.
Curly-leaf pondweed presents a complex challenge for Wisconsin’s aquatic ecosystems, necessitating a balanced approach to management. While it poses significant ecological and recreational concerns, it also provides some benefits in otherwise inhospitable environments. Effective management relies on prevention, informed mechanical and chemical control strategies, and ongoing research to mitigate its impacts while preserving the health of Wisconsin’s lakes and rivers.
Learn more about invasive species in Wisconsin.
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Author: News Desk
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