Curly-leafed Pondweed is an exotic, invasive aquatic plant that was first reported in Indian Lake in May, 2017. Curly-leafed Pondweed (CLP) can rapidly spread and form extensive stands that will grow to the surface. Recreational activities such as boating, swimming, and fishing can be eliminated from these areas. The adverse effects can reduce property values if CLP infestations are not managed.
CLP is most easily identified by the characteristic leaves that have what is described as an undulating, wavy, or crinkled along with fine serrations (see links below). CLP is typically the first plant observed in the spring as it starts growing in late fall and through the winter under the ice. Since it can grow in waters as deep as 15 feet, it has the potential to grow anywhere in Indian Lake. Flowering takes place in late spring to early summer. Flowers are formed on stems that protrude out of the water for several inches.
CLP can grow from plant pieces, seeds, or turions (a vegetative propagule). Because it grows under the ice all winter, CLP has an advantage over native plants that develop later. Dense stands will crowd out native plants and eliminate them. The growing plants will form a strong rhizome in the sediment. Around the same time as flowering occurs, the plants will form up to one hundred turions. The turions can be dispersed and appear to be a significant factor in the spread of CLP in a waterbody.
Following flowering in late spring, the population collapses in June or July. Dying plants can cause reduced oxygen levels in the water as well as rapidly releasing nutrients. The abundance of available nutrients can produce significant algal blooms. By late fall, regrowth begins from the rhizomes and turions. Even with effective chemical control of the plants, new growth from buried turions can occur for several years. One report indicated turions can be viable for up to five years.
Once CLP has infested a lake, eradication is not a realistic goal. At best, management of the adverse effects can be expected. Typical management is through mechanical harvesting and/or chemical treatment with herbicides like diquat or endothall. For mechanical harvesting to be effective, it must be timed so that it occurs prior to turion production. Since some plant fragments can develop into new plants, it is important to use an efficient harvesting method. Chemical treatments also need to be applied prior to turion production, typically when the water temperature reaches 50-55F.
Following discovery, a search was conducted to find additional infestations. These were treated in 2017 and 2018. No infestations were found in 2019 or 2020. CLP was again detected in 2021. In order to avoid future infestations, boaters are reminded that they need to wash boats and trailers, drain and rinse live wells, and flush engines, particularly personal watercraft, before launching.
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