• Home
  • Specie
  • Beginner’s Guide to Invasive Species

Beginner’s Guide to Invasive Species

By on November 5, 2021 0

Antonius R. Chess Jr., Cornell Co-op Extension of Yates County


Invasive species have become a serious problem in the United States. Invasive species are organisms that are not native to an ecosystem and spread quickly. Their characteristics allow them to supplant native species in an ecosystem, reducing species diversity. According to the National Wildlife Federation (NWF), there are over 4,000 invasive species in the United States and 42% of threatened or endangered species are endangered. Human health and the economy are also affected by invasive species.


Before we can prevent the spread of an invasive species, we must understand the causes of their spread and the impacts. According to the NWF, human activity is the main cause of the spread of invasive species in new environments:

● Commercial and pleasure vessels carrying aquatic organisms in ballast water

● Transport of wood containing eggs or larvae. Even the pallets and wooden crates on the shipping goods carry eggs or larvae.

● People who buy ornamental plants

● Climate change affecting the capacity of an ecosystem to accommodate new species

When an invasive species enters a new environment, there may be no natural predators or controls to naturally mitigate the spread. According to the Fish and Wildlife Service (FWS), the potential impacts of an invasive species on an ecosystem include:

● Tackle native species

● Compete with native species

● Destroy or replace the food source of other species

● Spread of the disease

● Increased soil erosion

● Habitat degradation

Invasive species also have an impact on the economy and public health. The FWS lists the ways they affect us:

● Block waterways for boating, fishing and other recreational activities

● Spread into agricultural environments and invade fields, some posing risks to farm animals and reducing crop yields

● Damage to power plants and industrial water systems

● Reduce the income of companies based on natural resources

● May be toxic to humans (eg giant hogweed)

● Carry diseases

Some invasive species causing problems in New York City include the spotted lantern fly, star stanza, black and pale swallow, and hydrilla.


Native to Asia, the spotted lantern fly (SLF) is an invasive insect that made its way to the United States in 2014. They are about an inch in length and a half inch in width; Gray and black fore wings with contrasting red and black spots on the hind wings and a broad abdomen. According to Penn State Extension, SLF feeds on the sap of more than 70 different plant species. As the SLF feeds, it releases a sweet substance called honeydew which causes mold to form on the plant, interfering with photosynthesis. According to the Department of Environmental Conservation (DEC), SLF is mainly spread by laying eggs on vehicles, firewood, stones and other transportable outdoor goods.

To manage the spread of SLF, quarantines have been put in place to restrict the movement of goods from any county with evidence of breeding colonies. The Ministry of Agriculture and Markets (DAM) conducts shipment inspections and trapping surveys in high risk areas. The DEC has established prevention zones for early surveillance in nearby counties.

To help prevent the spread of SLF, inspect your vehicles and equipment while traveling. If you think you’ve found the SLF, email [email protected] with the location, nearby roads, and / or GPS coordinates.


Star stonewort (SSW) is native to Europe and western Asia and grows submerged in lakes, ponds and slow rivers. To identify SSW, look for whorls of 4-6 twigs. Bulbs produced at nodes in mid-late summer are white and star-shaped. It spreads in fragments attached to boats, trailers and anchors. According to the DEC, the SSW has expanded to 14 counties in New York City.

Star stonewort grows along a lake bottom.

The threat is the formation of dense mats in lakes that can:

● Reduce the biodiversity of aquatic plants by supplanting them

● Prevent fish movement and spawning activity

● Reduce fish habitat

● Disrupt water flow and chemistry

● obstruct waterways

Chemical methods such as the use of herbicides and mechanical methods such as uprooting and harvesting are used to help manage the spread. Additionally, boat stewards educate boat users about aquatic invasive species and inspect boats for vegetation to help prevent their spread.

To help prevent the spread of SSWs, it is important to inspect, clean, drain, and dry your watercraft, as well as your equipment, after each use. If you find it, report it to your local DEC office or cooperative extension and throw the sample in the trash.


Also known as the dog strangled vine, the swallow is a perennial climbing vine that grows in a variety of environmental conditions. According to Cornell Cooperative Extension (CCE), the plant arrived in the United States as an ornamental for horticultural purposes. They emerge in spring, flower in early summer, and produce seeds in late summer. The DEC states that they are capable of self-pollination and can produce 1,000 to 2,000 seeds per year which are spread by wind. Herbivores tend to avoid swallow must because it is difficult to move around.

Blooming Black Swallow (left) and Pale Swallow (right).  The flowers have spread throughout the northeastern United States and southeastern Canada and appear further west.

St. John’s Wort infestations can result in loss of habitat, food sources, biodiversity and damage to microbial communities. Pale swallow, which is most common in New York City, negatively impacts the monarch by supplanting and displacing milkweed and swallow is not a viable alternative for monarchs to lay eggs. Management practices include mechanical, chemical and biological control. Mechanical controls include harvesting and disposal, as well as mowing to prevent seed formation. Chemical herbicides are used on cut stems. Hypena opulenta, a moth that has recently been accepted as a biological control method for swallow’s wort in the United States, feeds on leaves, inhibiting photosynthesis.


This submerged perennial was first introduced to the United States as an aquarium plant from the Indian subcontinent, Sri Lanka. In the United States, it can grow in freshwater lakes, ponds, rivers, reservoirs, and canals.

Hydrilla epidemics are being managed in Tompkins County.

Hydrilla is spread by fragmentation of the stem. The fragments stuck to the boats allow the propagation and growth of buds and tubers in new environments. Hydrilla can grow in deep water, with little or no competition with other plants. In the absence of competition, they grow in dense mats up to 25 feet, blocking sunlight from other plants. This reduces the growing space available for other plants, resulting in a decrease in native vegetation, open water, waterfowl foraging areas and fish spawning grounds. Hydrilla also annoys boaters and swimmers, can stratify the water column and decrease dissolved oxygen levels.

Hydrilla has sharp, bright green leaves that grow in whorls of four or more, and are usually serrated or toothed. They have thin stems and a single floating white flower. Boat stewardship programs help monitor boat vegetation, including hydrilla, but it is important that you inspect, clean, drain, and dry your boat, as well as your equipment, after each use.


Prevention is the best way to stop the spread of all invasive species so let’s work together! Join the fight against invasive species by downloading the “iMapInvasives” application and publish your findings on a shared database.

Consider joining the Regional Invasive Species Management Partnerships (PRISM) email list through the website http://nyis.info/prisms/ for information and updates on invasive species and / or to volunteer with Finger Lakes PRISM (http://fingerlakesinvasives.org/). For other opportunities, contact your local Cornell Cooperative Extension office.

Source link

Leave a comment

Your email address will not be published. Required fields are marked *