USDA. Blog.

Humans adores trees. But humans also migrate and trade, habits that led to the accidental introduction of insects and diseases that harm trees and alter the landscape. Examples are easy to find and may be outside your front door: American elms that once dotted streets across America succumbed to Dutch elm disease. Now all colors of ash species – black, green, white, pumpkin, and blue – are threatened by emerald ash borer. The already uncommon butternut tree, also known as white walnut, faces the possibility of extinction from a mysterious attacker. Many invasive insects and fungi come from regions where native trees have evolved to resist their attacks. When these species enter the United States, they find trees that lack this resistance. There's no immediate end to this dismal pipeline, but there is hope on the horizon.

USDA. FS. Northern Research Station.

The Alien Forest Pest Explorer (AFPE) is an interactive web tool which provides detailed spatial data describing pest distributions and host inventory estimates for damaging, non-indigenous forest insect and disease pathogens currently established in the U.S. The database is maintained as a joint effort of Purdue University, the U.S. Forest Service Northern Research Station, and the U.S. Forest Service Forest Health Protection.

USDA. Forest Service.

Once common across eastern North America, the American elm is deeply ingrained in our nation's history. However, a large portion of the tree population was affected by Dutch Elm Disease beginning in the 1930s. Today, short-lived elms can still be found in forests, but because they tend to be much smaller, they no longer play such an important ecological role. A multifaceted collaborative effort is underway to restore the stately and once dominant American elm to persist on the landscape of the nation's forests.

Oregon State University. Extension Service.

USDA. FS. Northern Research Station.

Ash and elm trees play important roles in the U.S. economy, culture, and environment. In the eastern United States, elm (especially American elm) and ash trees are in trouble because of two threats: the emerald ash borer (an insect that attacks ash) and Dutch elm disease (caused by a fungus that sickens elms). These pests are causing ash and elm trees to die off quickly. Because elm and ash trees serve important ecological roles where they are found, the loss of these trees can lead to profound changes across urban and rural environments.