Thousands of trees are struck by lightning every year. These trees will have varying degrees of damage ranging from complete shattering and destruction of the tree, to a slow lingering death, to virtually no apparent damage at all (Figure 1).

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

Conifers are commonly planted in North America to provide year-round screening, as windbreaks or as focal trees in the landscape.

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.

ManagementEmerald ash borer (Agrilus planipennis) was first discovered in southeastern Michigan in 2002.

• 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.