AIS / Fisheries

June AIS: Curly-Leaf Pondweed

Best Detected in the spring because it forms new plants under the ice in the winter, making it one of the first aquatic plants to emerge in the spring. Best controlled in the spring or early summer when native species are still dormant and temperatures are low enough for endothal herbicides to be effective.

Curly-Leaf PondweedDescription

  • Found in alkaline, high nutrient waters
  • Tolerates low light and low water temperatures which allows it to outcompete native plants in the spring
  • Prefers soft substrate and shallow water depths
  • Leaves reddish-green, oblong, and wavy, 1-3in. long, finely toothed edges
  • Grows submerged in up to 4 meter deep water, with flowers forming in shallow (<1 foot of water)
  • Native to Eurasia, Africa, and Australia

Life History

  • Produces turions: small hardened stem tips that disperse along waterways. Lay dormant during the summer, germinating when native plants die back. One plant produces hundreds
  • Also reproduces from rhizomes/stem fragments
  • Drops to lake bottom in mid-summer

Why Is It A Problem?

  • Tolerant of low light and low water temperatures so it has a head start on and outcompetes native plants in the spring. SPREADS RAPIDLY!
  • In mid-summer, the plants die off resulting in a critical loss of dissolved oxygen; piling of plants along the shore; and increased phosphorus concentrations that cause algal blooms
  • Forms dense surface beds that outcompete native aquatic plants and interfere with aquatic recreation

What Can Be Done?

  • Manual/ mechanical control: Reduce/ eliminate trions to interrupt life cycle
  • Raking/handcutting to remove plants at the sediment surface to prevent turion production
  • Harvesting the top 5 ft of plant
  • CAREFUL! Also spreads through fragments!
  • CLEAN YOUR BOATS/ EQUIPMENT!
  • Chemical control: spring or early summer
  • Chemicals can be used and knock down plant within 14-30 days
  • Maintaining healthy ecosystem diversity and minimizing nutrient/ pollutant inputs deters invasion
  • Drawdowns kill plants by exposing them to freezing temperatures and desiccation. But, this high level of disturbance creates favorable conditions for the invasion of other invasive species so it is not preferred

Note: DNR permits are required for chemical treatments, mechanical treatments, some manual treatments, biological control, bottom screening, and buoy/barrier placement.