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Invasive Species

Hundreds of species of non-native (aka alien or exotic) invasive forest insects, diseases, plants, and other organisms are established in the United States. Some of these species have become invasive, spreading rapidly and causing significant economic and ecological impacts to the nation's forest and urban trees. Northern Research Station scientists work to understand the biology of invasive insects and diseases as well as possible controls, and develop tools that help everyone from land managers to homeowners make their trees healthier. In addition to studying and monitoring the nonnatives already here, scientists are monitoring pests that have potential to become problems if they arrive, whether from overseas or just other parts of the country. Invasive pests are often moved around the country in firewood and lumber, on vehicles, and on nursery stock.

Invasive Insects

Artwork for Alien Forest Pest Explorer

Alien Forest Pest Explorer is a web-based portal for the exploration of spatial data describing the ranges of invasive forest pests established in the United States.


Additional Research Studies

Additional Emerging Threats

The following invasive insects are considered potential threats to North American forests based on their interceptions at ports or in manufactured goods. Rapid detection and response to newly arrived insects helps facilitate eradication. Here’s a list of potential pests of greatest concern with links to external information resources:

Invasive Plants

Emerging Threats

The following invasive plants are considered potential threats to the Midwestern and Northeastern forests based on noted invasiveness in states bordering our region.  In some cases, the species is already found in localized areas in our region and is a known invader in other countries. Rapid detection and response to newly arrived plants helps facilitate eradication. Here’s a list of potential invasive plants of greatest concern with links to external information resources. 

  • Hardy kiwi vine (Actinidia arguta) - Tolerates cold temperatures.  Promoted by several state agricultural extension services, unaware of its capacity to spread. Can germinate and grow under a closed canopy and climb surrounding vegetation, eventually killing its support. The vine then spreads to surrounding trees.  Invasiveness is variable and in question; needs further observation.
  • Sickle weed (Falcaria vulgaris) - Demonstrated ability to establish and spread beyond its native range, such as in several countries in northern Europe.  In the US, it has spread within and across South Dakota and is found in localized populations in states within our region. Produces thousands of viable seed, forms dense populations, and regenerates from root fragments. Recommended for eradication in Nebraska and Wisconsin.
  • Chinese parasol tree (Firmiana simplex)- An aggressive, invasive weed in the warmer locations.  Self-fertile, and its seeds spread readily, especially along watercourses, growing rapidly after germination in favorable sites. Primarily southern species but now also located in Maryland.
  • Cogon grass (Imperata cylindrica) -Able to invade both moist and dry upland pine forests. Once established it often forms dense monoculture.  Primarily in southern states but apears to be moving north (and thought likely to do so with climate change).
  • Glossy privet (Ligustrum lucidum) - Fast-growing evergreen tree with a dense canopy of bending branches composed of glossy green leaves; eaves and fruit are poisonous to humans.  Has the potential to replace mid-canopy trees in forests and dominate a forest. Found in a boarding state.
  • Leatherleaf mahonia (Mahonia bealei) - Leatherleaf mahonia.  Evergreen; primarily invasive in southern states but has been found escaping in Maryland. Drought and shade tolerant, but can grow in the open sun.
  • March dew flower, marsh day flower; wart-removing herb (Murdannia keisak) - An annual, emergent plant that invades wetlands in the southeastern and northwestern United States. Plant stems are succulent, form roots at the nodes, and grow prostrate along the ground. Found locally in Maryland and New Jersey.
  • Wavy basketgrass (Oplismenus hirtellus ssp. undulatifolius) - Wavy basketgrass. Has demonstrated a capacity to establish and spread in Maryland and Virginia. The most notable characteristics contributing to its high establishment/spread risk score include self-compatibility, a short generation time and sticky propagules that promote dispersal.  Shade tolerant.
  • Itch grass (Rottboellia cochinchininsus) - Now widespread in the tropics and subtropics worldwide. Introduced into the United States for potential forage in the 1920s. It has been reported in Alabama, Arkansas, Florida, Georgia, Indiana, Louisiana, Mississippi, North Carolina, Virginia, and Texas. Field studies indicate that itchgrass may grow and produce seed as far north as Minnesota. Despite efforts to map and monitor its spread, the full extent of its invasion is not clear.
  • Chinese toon, Chinese mahogany (Toona sinensis) - Potentially spreading in woodlands near Philadelphia, PA.  Not declared an invasive species elsewhere, but is naturalized in Japan. We advise to keep watch on this species.

Invasive Diseases

Emerging Threats

The following fungal diseases are already present in other parts of North America and could move into eastern hardwood forests. Researchers are studying the potential dangers of the diseases in the East and South.

  • Sudden Oak Death or ramorum blight-, a fungal disease that has been killing tanoaks and oaks along the West Coast since the mid-nineties, also affects many shrub species with leaf cankers, without killing these species. Some of these shrubs are involved in horticulture (Rhododendron, Camellia, and Pieris spp.) and could vector the fungus to the East, where there are many potentially susceptible tree and shrub species.
  • Laurel Wilt, a disease first found on redbay (Persea sp.) in 2003 and members of the Laurel family, is a fungus vectored by the redbay ambrosia beetle and has been found in the Southeast.
Last Modified: April 7, 2016