Ash tree species in North America are under mortal threat from the Emerald Ash Borer (EAB), now in 35 states and five Canadian provinces.

The horticultural trade relies on healthy plants to flourish. However, its very nature
means that it is also a key pathway for the introduction and spread of plant pests and diseases.

European ash is a significant tree commercially, ecologically, and culturally. It is currently
threatened by two invasive species, the fungus that causes ash dieback and

Oak decline is a slow-acting disease complex that involves the interaction of biotic and abiotic factors such as climate, site quality and advancing tree age.

Interception of potential invasive species at ports-of-entry is essential for effective biosecurity
and biosurveillance programs. However, taxonomic assessment of the immature stages

Ice or snow loads can cause branch breakage or failure of entire trees and shrubs. Branches or entire trees that fall in storms can impact homes, vehicles, power lines and block roads.

In August 2008, a dangerous pest, the nonnative, invasive Asian longhorned beetle, was discovered in Worcester County, Massachusetts.

• Many exotic plant pests and pathogens are unknown prior to their establishment, making prevention and management difficult.

The invasive hemlock woolly adelgid (HWA) has decimated hemlock stands across much of the eastern United States, and presents a significant threat to all eastern hemlock in Canada across Ontario, Quebec, New Brunswick, Nova Scotia, and Prince Edward Isl

Insect and disease infestations pose major threats to several North American forest tree species.