Shipshewana Lake Weeds
Aquatic plants are a beneficial and necessary part of lakes. Without them, most other organisms cannot survive. Plants keep the water oxygenated, provide food, cover and nesting sites, and stabilize the shoreline and lake bottom. Unfortunately, nonnative plants that are introduced to new habitats often become a nuisance by hindering human uses of water and threatening the structure and function of diverse native aquatic ecosystems.
Over the years 2021 & 2022 weed growth in Shipshewana Lake increased drastically. This is due, at least in part, to the increasing clarity of the water allowing sunlight to reach the lake bottom. Ironically, that clarity is enhanced by the growth of weeds absorbing nutrients. The weed growth began to impact the usability of the lake and the Shipshewana Community Lake Improvement Association (SCLIA) contacted Aquatic Weed Control to determine what we can do to control/manage the weeds in our lake. During a brief survey of the lake, we identified five aquatic weeds reproducing in Shipshewana Lake (may not be 100% inclusive). The most prominent weed in the lake appears to be Coontail. We also identified Eurasian Watermilfoil; Duckweed; Naiads; and Waterlettuce. Through Aquatic Weed Control we received a permit from the Indiana Department of Natural Resources (IDNR) to treat approximately 10%, or up to 20 acres, for the Coontail.
In 2023 a small portion of lake front residents took advantage of the weed control proffer and we treated approximately 3% of the lake for Coontail. This treatment appeared to work really well for the small amount of participation and SCLIA will facilitate the same type of treatment in 2024 and beyond as necessary.
Offer for users of Shipshewana Lake
Many people enjoy shoreline fishing at Shipshewana Lake. The only planned public areas for weed treatment are in front of the boat launch and the Shipshewana Lake Park. That treatment will be paid for by SCLIA. If there are any acres available for treatment after lake front homeowners have signed up (in 2023 this amounted to approximately 3% of the lake, leaving another 7% available for treatment), SCLIA will accept applications from individuals or groups who would like additional “public” shoreline areas treated. These additional treatment areas must be paid for by the applicants. The cost of these treatments will be posted as soon as SCLIA receives notice of the 2024 price. If you are interested, please email SCLIA at firstname.lastname@example.org and include the public area of the lake you would like to see treated.
Below are descriptions of the five weeds observed in Shipshewana Lake.
Coontail, sometimes called “Hornwort” is a common, dark green, submerged perennial aquatic plant and is a native plant to Indiana. While it lacks true roots, Coontail may be loosely anchored to the bottom by specialized, finely divided, buried or free-floating stems. The fan shaped leaves are relatively stiff and best observed in the water. They are arranged in whorls of five or more, with many forks and small teeth along the edge or midrib giving the plants a rough feel. The plants grow long and sparse and may reach lengths over 15 feet but are often bushy near the tips giving the plant a “raccoon tail” or “Christmas tree” like appearance. They are often confused with water milfoil or fanwort, but Coontail leaves are spiny and forked rather than featherlike. Coontail’s flowers are very small and rarely seen. Reproduction is either by seed or by vegetative growth of plant fragments. Tiny flowers are located at the leaf base on very short stalks that never reach the surface. Pollination occurs underwater. Coontail pollen has adapted to being wet and can complete its entire lifecycle underwater producing a small, hard, oval seed with three spines. It reproduces by seed formation and fragmentation. Fragmentation allows the plant to re-sprout and grow into new plants and they may overwinter or remain dormant in the sediment for long periods of time.
Coontail has tremendous value as a year-round habitat plant for young fish such as bluegill, perch and largemouth bass, as well as small aquatic insects. Some fish and waterfowl eat its shoots and seeds, although it is not considered an important food source. Coontail is a competitive plant that can develop dense subsurface mats in high nutrient waters and displace or out-compete other native vegetation. It can reach nuisance levels, causing dense mats to deplete oxygen levels that can lead to fish kills, impede recreational activities, and create mosquito habitats. Due to its ability to absorb nutrients from the water, coontail does provide a water quality benefit and may help to improve water clarity.
The fruits of coontail are consumed by ducks and it is considered a good wildlife food. Submerged portions of all aquatic plants provide habitats for many invertebrates. These invertebrates in turn are used as food by fish and other wildlife species (e.g. amphibians, reptiles, ducks, etc.). After aquatic plants die, their decomposition by bacteria and fungi provides food (called “detritus”) for many aquatic invertebrates.
Eurasian watermilfoil is an invasive species rooted in the sediment that grows completely underwater as a submersed plant that can form a dense canopy on the water surface. The species is commonly found in water from 1 to 15 feet in depth but can occur at depths of up to 30 feet if the water is extremely clear. Eurasian watermilfoil is an evergreen perennial plant that produces persistent green shoots throughout the year and overwinters as root crowns. Leaves are feather-like, with each leaf composed of 14 to 24 pairs of leaflets arranged in whorls (groups) of four at the nodes of the stem. Stems and plant tips may appear reddish, but color is not consistent and may vary based on a number of factors, including environmental conditions. Flowers form on short aerial stems that hold them above the water and have both pollen-bearing (“male”) and seed- producing (“female”) flowers. Flowers are wind-pollinated and produce up to four nutlets per flower. Eurasian watermilfoil is difficult to identify and is often confused with several native species.
Because Eurasian watermilfoil grows entirely underwater as a submersed aquatic plant, the range of water depths the species can inhabit is limited by light penetration and water clarity. A dense canopy often forms at the surface of the water, which interferes with recreational uses of water such as boating, fishing and swimming. In addition, excessive growth of the species may alter aquatic ecosystems by decreasing native plant and animal diversity and abundance and by affecting the predator/prey relationships of fish among littoral plants. A healthy lake is damaged because heavy infestations of Eurasian watermilfoil lower dissolved oxygen under the canopy, increase daily pH shifts, reduce water movement and wave action, increase sedimentation rates and reduce turbidity.
Although duckweeds are often a nuisance in backyard ponds, the plants are valued and used extensively for applied and basic plant science research. Duckweeds have many potential uses, including biofuel production and as a food source (duckweed reportedly tastes like spinach and is high in protein and vitamins). Duckweeds have also been used as bioremediation agents to remove waterborne nutrients and contaminants. These species can improve water quality in natural systems such as lakes and can reduce nitrogen, phosphorus and metal contamination in commercial waters such as swine-based effluent ponds before they are discharged to other waters, although this could accidentally introduce duckweeds to downstream systems.
Similar to filamentous algae, duckweed can form dense surface mats that are several layers thick and may include mixtures of different species. However, duckweed’s ability to decrease light penetration and intensity and to consume nutrients can actually inhibit algal growth. Dissolved oxygen concentrations below duckweed mats are often low, which can influence the type and abundance of invertebrate and fish populations. Duckweed mats can also reduce aesthetics and recreational uses of water resources because their excessive growth covers the surface of the water. Duckweed usually causes problems in smaller bodies of water such as backyard ponds, canals, wetlands and other static sites.
Naiads are slender, narrow-leaved plants that grow completely under water and are rooted to the bottom. The leaves are slender, have finely toothed edges, and occur in pairs or whorls, with each leaf base swollen to form a sheath around the stem. There are tiny greenish flowers at the leaf bases.
Naiads are an important food for waterfowl, which eat the seeds. As with other submerged aquatics, naiads provide shelter for young fish and other aquatic organisms.
Only spotted at one spot on Shipshewana Lake (as of 9-20-22). The species is considered one of the world’s worst weeds and is a noxious species in most regions where it has been introduced, such as Hawaii, Australia and the Canary Islands. In addition, waterlettuce is considered invasive in the US, Puerto Rico and Africa, despite reports that the species could be native to these areas. The USDA considers waterlettuce to be native to the continental US and does not categorize the species as a noxious weed. Waterlettuce spreads very rapidly and can double its population size in as little as a few weeks, so it can quickly cover the surface of invaded waters. The species is not cold- hardy and rarely establishes permanent populations in temperate areas. Waterlettuce will survive moderate freezes but requires temperatures of greater than 50 °F to produce new growth.
Waterlettuce is a floating flowering monocot that grows as an annual (in temperate regions) or as a perennial (in tropical and subtropical climates) in all types of bodies of water. Muddy or turbid water often limits growth of submersed plants, but since waterlettuce is a floating plant, it is unaffected by these conditions. The leaves of waterlettuce have wavy or scalloped margins and are thick, light green, covered with short hairs and water-repellant. Each leaf can reach up to one foot in length; leaves are attached to one another at the plant’s base to form a free-floating rosette (although plants will sometimes root in soft saturated sediments when stranded by drought or wave action). The white to tan roots of waterlettuce are long and feathery and hang beneath the rosette of leaves. Waterlettuce grows throughout the year in the tropics, but freezing temperatures kill the leaves of the plant in the northern portions of its range.
The best method to control waterlettuce is to prevent the species from entering a water body. Waterlettuce is not on the Federal Noxious Weed List. However, waterlettuce is on the State Noxious Weed Lists of Alabama, California, Connecticut, Florida, Puerto Rico, South Carolina and Texas, so its sale and transport is prohibited in these states. Even in states where waterlettuce is listed, it is easy to purchase plants at farmers’ markets, local plant sales, on the internet and from other unregulated sources. Although waterlettuce has been deemed eradicated in some invaded areas such as small field sites in New Zealand, it is difficult or impossible to completely eliminate waterlettuce once a larger body of water has been invaded. Between existing populations that are left uncontrolled, accidental transfer from infested areas and escapes from cultivation, waterlettuce still manages to slowly increase its range and to colonize new bodies of water.