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Emerald Ash Borer Background Information

Section Two

Where did EAB come from, and why is it a problem?

An exotic species is one that is not naturally found in an ecosystem.  An invasive species is a plant, animal, or pathogen that comes from another place and, once established, is likely to cause economic and/or environmental harm. Before June 2002, EAB had never been found in North America. 

The natural range of the emerald ash borer (Agrilus planipennis) is eastern Russia, northern China, Japan, and Korea.  EAB is considered a secondary pest if found within its natural range.  This means that the borer co-evolved with the ash tree so that there are predators, parasites, diseases, and environmental conditions that keep the population under control in its native land.  It also means that it usually feeds on stressed or dying trees. 

But in North America, EAB is considered a primary pest.  This means that it spreads readily, and beetle populations can increase quickly and destroy thousands of trees in a relatively short time.  In other words, EAB attacks all kinds of ash trees, whether they are healthy or stressed, and feeds on them until they die, and there is nothing in place (parasite, disease, or environmental condition) to stop the destruction. More info on EAB website