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Invasive Species

Invasive species means a species that is not native (i.e., an alien) to a particular area or ecosystem and whose introduction causes or is likely to cause environmental or economic harm to the new area or even harm to human or animal health. Invasives can move aggressively into a habitat and monopolize resources such as light, nutrients, water and space.  They compete with and have a negative effect on native plants and reduce the quality and quantity of wildlife habitat “habitat loss” resulting in environmental (ecological) degradation.  They can also negatively impact farm crops contributing to the economic losses.  While many of the invasive species that we may encounter are plants, insects and animals can also be invasive.

Natives vs. Invasive Species:Native speciesare those that are well established in a geographic area. Only plants or animals found in this country before the arrival of European settlers are considered to be native in the U.S. Any species arriving later are considered to be non-native. Some non-native plants have become “Naturalized Plants”. That meansthat have spread into the non-native environments and are able to reproduce in their new home and eventually establish a new population there.While a plant may have become “naturalized”, it is still considered to be a non-native. Most of the naturalized, non-native plants are well behaved and are not problems. Examples include Black-eyed Susan and Lily-of-the Valley, that are not native to the U.S. Our beloved naturalized daffodils are such a well-behaved alien, that we don’t even think of them as being non-native. However, a small number of naturalized, non-natives become invasive. The non-native species that become invasive are organisms that have distinctive advantages that enable them to spread in the local ecosystem. They typically do not have the natural controls such as herbivores (plant eating animals), parasites, pathogens, predators etc. that occur in their native range. In our region, for example, while white tail deer are eating many of our native plants, they tend to avoid eating the invasive plants thus giving the invasives a major advantage. Invasives may also possess many traits such as the ability to establish, grow and reproduce rapidly, that help them out-compete the native species.

Humans are primarily responsible for the introduction and movement of invasives in the U.S. and that introduction could be deliberate or accidental. Many invasives plants such as Japanese Barberry and Burning Bush were brought into the U.S. as ornamentals to enhance yards and gardens while Multiflora Rose was brought in as a root stock for ornamental roses. At that time of their introduction, people did not recognize the potential damage that could ultimately occur by bringing in “aliens”. Modern means of transportation brings goods, people and invasives to all reaches of the globe. Insects and seeds from invasives have arrived from abroad in packing materials. Ballast water from ships is to blame for introducing many invasive organisms to the waters of North America etc.

Harm Caused by Invasive Species:Invasive plants can crowd out the native plants that are essential for the continuation of a healthy and diverse ecosystem. Native plants provide foodand shelter for mammals, birds and insects that depend on the native plants. Insects and their larvae feed on the native plants. Birds, in turn, depend on the insects and their larvae for food. Many songbirds also depend on the fruit of some of the native shrubs for food. Loss of native plants, therefore, leads to a decrease in insects as well as a decrease in our bird population. Invasive insects like the Emerald Ash Borer are killing our Ash trees. Invasive plants that are taking over the forest floor, also interfere with the growth of tree seedlings having a long-term negative effect on the structure of our forests and the environment.Invasive species can have a large economic impact. In the most widely referenced paper on this topic, the late Prof. David Pimentel of Cornell University, College of Agriculture and Life Science, projected that invasive species cost the U.S. economy more than $138 billion annually. Agriculture is being particularly hard hit by invasives with crop damage from competing invasives and crop plant diseases and pathogens. Invasive species can also have negative effects on the health of humans and animals. The invasive plant Giant Hogweed, for example, can cause severe burns and even potential blindness.

New York State Regulations:Because of the harm and potential harm caused by invasive species, New York State’s Department of Environmental Protection (DEC) has developed regulations that are meant to reduce the introduction and spread of invasives. Invasives being addressed by the DEC fall into two categories. For any species falling in the Prohibited category, it is unlawful to buy, sell, transport or introduce (e.g., propagate) that invasive. Regulated invasive species, on the other hand, are species which cannot be knowingly introduced into a free-living state (such as park land) or introduced by a means that one should have known would lead to such an introduction. However, it is legal to possess, buy, sell, propagate and transport invasives that fall in the Regulated category.

Below are afew common invasive species that you may see in your yard.Check out the New York State Prohibited and Regulated Invasive Plants or the New York State Prohibited and Regulated Invasive Animals brochures for photos http://www.dec.ny.gov/animals/99141.html

Invasive Plants:

Garlic Mustard

  • Aggressive invasive herb that crowds out natives and other plants and is one of the worst invaders of forests in the Northeast
  • Produces chemicals that inhibit the growth of other surrounding plants
  • Biennial i.e., lives for two years
  • First Year: Short, dark green, kidney-shaped leaves with scalloped edges.
  • Stays green all winter allowing easier identification
  • Second Year: Taller stem shoots up early in the year
  • Develops new, toothed, triangular leaves
  • Small, white flowers develop early in April
  • Goes to seed by mid-late May; seeds may stay in the soil for five years
  • Pull plant (with hand close to ground) plus all of the white, fleshy root when the ground is soft during the first season or before plant flowers and goes to seed in May of second year
  • Dispose of everything with the possibility of seed in garbage

Japanese Stilt Grass

  • Light green annual grass with silver stripe down leaf axil
  • Can occur in small patches or spread to large, dense swaths
  • Weak stems that fall over; new roots grow at leaf nodule giving appearance of “stilts”
  • Very aggressive: Thrives as a weed in lawns and gardens and expands into dense stands of grass that prevent desirable vegetation from growing
  • Flowers and goes to seed in late summer to early fall
  • Pull as soon as located or mow in late summer before goes to seed

Mile-a-Minute Vine

  • Very fast growing, aggressive annual vine with light blue-green triangular shaped leaves
  • Starts as a delicate-looking little plant that can grow up to 25 feet in length in one growing season
  • Curved sharp prickles along the stems
  • Small white fruit that ripens to purple then blue, colored berries
  • Can cover existing vegetation and restrict light availability, potentially killing plants below; dense mats can also restrict establishment of new vegetation
  • Pull as soon as possible in the season when plants are small and with fewer barbs. Definitely want plants pulled out before plants go to seed in late Summer

Once invasive plants have developed flowers and seeds,

the pulled plants must be disposed of in the trash

Invasive Pests:

Emerald Ash Borer (EAB)

  • Small bullet-shaped, bright green, destructive beetle native to Asia
  • Attacks and feeds on all varieties of Ash Trees
  • Larvae of the beetle destroy the vascular system of Ash trees causing dieback and then death of the tree.
  • May see “blonding” effect i.e., bark flakes off when woodpeckers hunt for immature EABs under the bark
  • Trees infected with EAB have no natural defense and will die in 3-5 years; can die within one year where EAB is well established and the insect population high.
  • Currently killing large numbers of Ash Trees in Rockland County

Spotted Lanternfly (SLF)

  • Colorful, moth-like invasive insect just entering Rockland County
  • Favorite food source is Tree of Heaven but also feeds on the sap of a wide variety of plants such as grapevines, hops, fruit trees (e.g., apples) as well as hardwood trees such as maples
  • Adults lay eggs in masses that are about an inch long and are covered by a brownish-gray putty like substance that dries to be brown and scaly. The egg masses may be on any hard surface such as tree trunks, firewood, rocks, vehicles, outdoor furniture etc.
  • Freezing temperatures will kill adult SLFs but their egg masses survive and hatch in late Spring releasing huge numbers of nymphs
  • Significant threat to New York’s agriculture and forest health
  • Citizens are asked to look for Spotted Lanternfly and/or their egg masses.
  • If you believe you have located Spotted Lanternfly or its egg masses, take picture, note location and submit the info to https://agriculture.ny.gov/spottedlanternfly

This site also provides good photos and background information on SLF.

Jumping Worms

  • Asian worms brought to U.S. as bait; currently spreading in Rockland County
  • Light brown/gray in color with a “milky” colored band encircling the body
  • Thrashes violently when disturbed
  • Lives in top 2-4 inches of soil and voraciously devours the critical layer of organic matter that supplies vital nutrients for plants; has a major detrimental effect on forests and native plants
  • Leave abundance of castings resulting in the soil looking like coffee grounds; coffee ground castings can help I.D. presence of the Jumping Worms
  • Currently no viable control methods
  • If have jumping worms avoid moving plants or soil from your yard and report sightings at https://www.nyimapinvasives.org


1. Pimentel, D.; R., Zuniga; Morrison, D (2005). "Update on the environmental and economic costs associated with alien-invasive species in the United States". Ecological Economics. 52 (3): 273–288.

2. http://www.dec.ny.gov/animals/99141.html

3. https://agriculture.ny.gov/spottedlanternfly

Prepared by Ann Barry

The information, including any advice or recommendations, contained herein is based upon the research and experience of Cornell Cooperative Extension personnel. While this information constitutes the best judgement/opinion of such personnel at the time issued, neither Cornell Cooperative Extension nor any representative thereof makes any representation or warrantee, express or implied, of any particular result or application of such information, or regarding any product. Users of any product are encouraged to read and follow product labeling instructions and check with the manufacturer or supplier for updated information. Nothing contained in this information should be interpreted as an endorsement expressed or implied of any particular product.

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