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U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Invasive Species

Invasive Forest Insects

There are hundreds of species of non-native insects in our forests; several species, due to lack of host resistance and lack of natural enemies, have caused significant damage to our natural and urban forests. Infestations by non-native insects can significantly impact a host tree species, and have cascading impacts on other associated species in the environment. In our urban forests, non-native species can cause loss of tree canopy, and associated impacts on storm water runoff, heating/cooling costs and quality of human life. The introduction of non-native species is not new. Species such as the Lymantria dispar and European elm bark beetle have been in North America for more than 100 years, but in recent years there has been an increasing rate of new introductions causing impacts, such as the hemlock woolly adelgid, emerald ash borer and Asian longhorned beetle. Forest Health Protection works closly with partners in states and APHIS to detect, monitor and manage these non-native forest pests.

  • Lymantria dispar dispar
  • Emerald Ash Borer
  • Asian Longhorned Beetle

Learn more about invasive forest insects

Invasive Forest Pathogens

The introduction of exotic invasive tree pathogens to North America has resulted in large scale tree mortality and the replacement of once dominant native tree species. Sudden Oak Death, Laurel Wilt, White Pine Blister Rust, Chestnut Blight, Butternut Canker, and Dutch Elm Disease, all serve as grim reminders of successful establishment of invasives that have significantly altered our urban and forest landscapes. When invasive forest pathogens are introduced on trees that did not co-evolve with them the consequence is swift, dramatic, and typically fatal. Forest Health Protection works closely with Animal and Plant Health Inspection Service (APHIS), federal agencies, tribes, and other stakeholders to detect, monitor, and manage these invasive forest pests.

  • Sudden Oak Death
  • Laurel Wilt
  • White Pine Blister Rust

Learn more about forest pathogens

Invasive Forest Plants

Invasive plants are among the most serious problems affecting landscapes and communities across the United States. These plants not only threaten the ecological integrity and biological diversity of our forest ecosystems, but can result in significant negative economic impacts. The result can be loss and destruction of forage and habitat for wildlife, loss of available grazing land, diminished land values, lost forest productivity, reduced groundwater levels, soil degradation, increased risk of devastating wildfires, and diminished recreational enjoyment. In addition, nearly half of all species federally listed as threatened or endangered are thought to be at risk primarily due to the effects of invasive species.

  • Garlic Mustard
  • Giant Hogweed
  • Medusa Head
  • Albizia
  • Knotweed
  • Cheatgrass

Learn more about invasive forest plants

Emerald ash borer

Emerald ash borer. Photo by David Cappaert, Michigan State University,