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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.

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.

See also: Ground Covers, Trees, Shrubs, and Woody Ornamentals Fact Sheets for more resources

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.

See also: Ophiostoma ulmi

See also: IPM Scouting in Woody Landscape Plants for more pests and diseases

See also: Clinic Factsheets for more diseases