How fast does emerald ash borer kill trees in our forests?

Emerald ash borer (Agrilus planipennis Fairmaire) kills nearly every ash tree it encounters, as seen in this aerial view of a forest in Ontario, Canada (Image credit: Troy Kimoto, Canadian Food Inspection Agency, via

Agrilus planipennis Fairmaire, a shiny green beetle from Asia commonly known as the emerald ash borer (EAB), has taken North America by storm. Assisted mostly by people, but also by its own wings, EAB is rapidly spreading across urban and forested areas alike.

EAB-killed ash trees in urban areas are noticeable and require immediate attention, with either insecticide protection or removal. This maintains safety, aesthetics, and function of the urban forest. Trees that die in natural forests hardly require such vigilance. If dead ash trees aren’t likely to damage property or injure people when they fall, they can often be left alone. Also, in most hardwood forests, ash is relatively less common than other trees such as oak or maple, so the structural and functional loss to the forest canopy may be minimal.

Loss of ash has serious ecological and economic implications, however, as ash fruits and seeds are an important food source for wildlife, white ash wood is used for baseball bats, and black ash is used to make baskets. Given these environmental losses and that this invasive species seems capable of killing nearly every ash tree it encounters, finding out how much damage EAB has incurred in our natural forests is a pressing issue.

In their recent article in Biological Invasions, Randall S. Morin and fellow researchers in the USDA Forest Service, Northern Research Station used a national forest inventory database to measure just how destructive EAB has been so far in the United States.

Read the full story on Entomology Today.