Niagara County Soil & Water Conservation District

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Invasive Species


New York State Department of Environmental Conservation's Invasive Species List and Action Programs:





Hydrilla (Hydrilla verticillata)
Also known as water thyme, Hydrilla is a submersed perennial herb that has pointed, bright green leaves about 5/8 inches long. The leaves grow in whorls of 3 - 10 along the stem. The margins of the leaves are serrated (toothed). The underside of the leaf has a reddish central spine and one or more small spines that give it a rough feeling when rubbed between your fingers. Thin stalks from the stem end in a single, small, floating white flower at the water's surface. A key identifying feature is the presence of small (up to half inch long), dull-white to yellowish, potato-like tubers which grow 2 to 12 inches below the surface of the sediment at the ends of underground stems. These tubers form at the end of the growing season and serve to store food to allow Hydrilla to overwinter.
Growing up to 25 feet, the stems of this plant are rooted in the bed of the water body. With its rapid growth rate and ability to grow in freshwater lakes, streams, canals, and ponds, Hydrilla is highly invasive and can displace native aquatic vegetation. Once established Hydrilla forms thick, horizontal mats on the water's surface, in turn blocking out sunlight that other native aquatic vegetation depends on. These thick mats also impair recreational activities such as swimming, fishing, boating, and in severe cases intakes at water treatment facilities and power plants can be blocked.
To prevent the spread of Hydrilla boaters should follow basic clean boating techniques. Cleaning equipment, watercraft, and trailers before and after activities in the water will help ensure that you will not transfer unwanted plants or plant fragments into water bodies. Physical removal is also recommended if plant material is building up around your dock or shoreline property. Removed plant material should be disposed of in the trash. Should you discover Hydrilla in a water body, please alert the appropriate local agencies.


Water Chestnut (Trapa natans)
Not to be confused with water chestnut you can buy canned in a grocery store (different species), the European Water Chestnut (Trapa natans) is a highly invasive freshwater plant species. Growing in shallow areas (<16ft) of lakes, ponds, and slow moving streams & rivers, it can form dense mats of floating vegetation.
The European water chestnut is a rooted aquatic plant with submersed and floating leaves. Feathery submersed leaves form whorls around the stem; the 3/4 to 1 � inch glossy green floating leaves are triangular with toothed edges. Single, small, white flowers with four 1/3-inch long petals sprout in the center of a rosette. The plant�s cord-like stems are spongy and buoyant, and can reach lengths of up to 16 feet. The stems are anchored to the bed of the water body by numerous branched roots.
Adverse affects caused by water chestnut include reduced sunlight penetration, decreased native vegetation growth, safety hazards for boaters and swimmers, and diminished dissolved oxygen levels in the water. Reduced native plant growth combined with decomposition of the water chestnut result in these low oxygen levels, potentially leading to fish kills.
Early detection and rapid response to water chestnut infestations is the most efficient and cost effective course of action. Physical removal can be accomplished by volunteers hand-pulling the plant from canoes or kayaks. Harvesting before the plant forms ripe seeds can be incorporated into a long-term control strategy. Populations must be carefully monitored after removal as seeds can remain viable in sediments for long periods of time.


Japanese Knotweed (Polygonum cuspidatum)
Japanese Knotweed is a perennial, herbaceous shrub that grows up to 5 meters tall. It has hollow, bamboo-like shoots that are segmented. Stems are red or orange. Japanese knotweed grows in dense clusters that shade out light, preventing other plant growth. The stems die back each growing season, while extensive underground stems (known as rhizomes) can survive for decades.
Native to Asia, Japanese Knotweed was introduced to North America for ornamental use in the 1870's. Populations can be found throughout the entire state of New York. Knotweed is adapted to a wide variety of soil types and pH levels, and can be found growing along riverbanks, wetlands, disturbed areas, roadsides, woodlands, and grasslands.
Populations of Knotweed out-compete native plants for light and nutrients; forming dense, tall stands that prevent light from reaching the ground. With growth rates of up to 8cm a day, by emerging in early April Knotweed can outcompete native species for light resources. In addition, knotweed clogs ditches, break up pavement, and destroys flood control structures. Once established, knotweed is extremely difficult to control and eradicate. Early detection and removal of small patches is advised. Manual removal is effective on small infestations, while mechanical and chemical controls may be required for large infestations. Populations and infestations should be reported to the National Invasive Species Hotline at: 1-877-STOP-ANS (1-877-786-7267)


Phragmites (Phragmites australis)
Also known as common reed, phragmites is a wetland plant species that is found in every U.S. state. Growing up to 6-12 feet high, it forms dense stands and is a long-lived species. The seedhead is purplish or tawny with a flaglike appearance. Phragmites is commonly identified by its height.
Widely distributed, Phragmites is found ranging all over Europe, Asia, Africa, American, and Australia. Both native and introduced genotypes exist in North America. Growth starts in February in some locations, with flowers developing by mid-summer. Seed set occurs through fall and winter, with seed germination occurring in the spring on exposed moist soils. Phragmites also forms a dense network of underground roots which send out rhizomes allowing the plant to spread horizontally.
An excellent colonizer, Phragmites can form dense, monoculture stands that outcompete other native plant species. Wetland hydrology and wildlife can be altered adversely, and the increased biomass of dead grass can increase fire potential. Integrated pest management can involve chemical, physical, and biological controls. Phragmites cannot withstand heavy, prolonged grazing.



Emerald Ash Borer (EAB) (Agrilus planipennis)
The emerald ash borer was first discovered in the United States in 2002 in southeastern Michigan This Asian beetle infests and kills North American ash species (green, white, black, and blue ash). The adult beetles are roughly 3/8 to 5/8 inch long and have metallic green wing covers and a coppery red/purple abdomen.
Adult beetles may be present from May-September, but are most common in June and July. Each female lays approximately 30-60 eggs during an average lifespan. The eggs are deposited individually in bark crevices. Once the larvae hatch they chew through the bark and into the phloem and cambial regions of the ash trees. It is this activity that eventually leads to the death of infested trees. The larvae feed on the phloem for several weeks, creating serpentine galleries (S-shaped) which effectively girdle the tree. Unable to transport the nutrients that it requires, the ash tree usually dies within 2 to 4 years of becoming infested.
There are some signs and symptoms that may develop in cases of emerald ash borer infestation. The tree canopy may become increasingly thin as foliage wilts and branches die back. The trunk may exhibit jagged holes left by woodpeckers feeding on the ash borer larvae. Small, "D" shaped exit holes may be observed on the trunk where adult beetles have emerged. And epicormic shoots and branches may sprout on the trunk or branches. Emerald ash borer is a serious threat to North America's native ash tree populations. If you notice any of these signs/symptoms on an ash tree notify your state Department of Agriculture, State Forester, Cooperative Extension Office, or local Conservation District.

If you have any questions or have discovered a possible emerald ash borer infestation additional information can be found at: and search "emerald ash borer"
Call NYS DEC at 1-866-640-0652
Contact your county's Cornell Cooperative Extension

The Western NY Emerald Ash Borer Task Force

The Western NY Emerald Ash Borer Task Force (WEABTF) is a volunteer organization of forestry professionals, scientists, natural resource managers, local officials, and private citizens. The WEABTF has organized to facilitate a science-based response to the economic, ecological, and public safety impacts within the forests and communities of Erie, Niagara, Genesee, Wyoming, Allegany, Cattaraugus, and Chautauqua counties. If you would like to assist in the goals of the WEABTF please contact Sharon Bachman at :





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