New York State
Department of Environmental Conservation's Invasive Species List and Action
BELOW EACH INVASIVE SPECIES LISTED IS A LINK TO A USDA NRCS FACT
SHEET THAT CONTAINS PICTURES AND A MORE DETAILED DESCRIPTION.
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
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.
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
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.
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
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.
Purple Loosestrife (Lythrum
Purple loosestrife is an hardy, upright, perennial herb that may grow up to
7 feet tall. It develops a strong taproot and may have up to 50 stems
arising from its base. When in bloom, loosestrife exhibits showy purple
flowers that some find aesthetically pleasing. This plant is highly
invasive, and is commonly found in monocultures where it has infested.
Purple loosestrife provides few nesting materials for wildlife, little food,
poor cover, and causes annual wetland loss of 190,000 hectares in the United
States. In many areas where its populations have increased, wildlife species
have declined causing major changes in wetland communities.
Many considerations need to be taken into account with regards to
controlling purple loosestrife. Due to the prolific seed production and ease
at which the seeds are dispersed, individuals should contact their local
agricultural extension specialist or county weed specialist to learn what
control methods work best in their area. Purple loosestrife can also spread
vegetatively by resprouting from stem or rootstock cuttings; caution must be
exercised when considering manual or mechanical control methods.
Emerald Ash Borer (EAB) (Agrilus
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
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.
you have any questions or have discovered a possible emerald ash borer
infestation additional information can be found at:
www.dec.ny.gov 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 : firstname.lastname@example.org
USDA NRCS NY EMERALD ASH BORER WEBSITE-