The Emerald Ash Borer in the United States

Zwack James 125

Jim Zwack is Director of Technical Services for the Davey Institute, the research, training, and educational arm of the Davey Tree Expert Company. This US tree care business that has been engaged in the management of the Emerald Ash Borer since it was first identified in the United States in 2002. Jim outlines the historical background to his upcoming presentation at ICF’s 2015 National Conference: Tree Health, Resilience and Sustainability.

The Emerald Ash Borer (EAB) was first identified in the United States in 2002 in Detroit, Michigan. Researchers believe the insect was transported into the US in wood packaging material from Asia, and that it was likely present as early as 10-15 years prior to the discovery. It attacks healthy and stressed trees alike, and all of the most common forms of ash in the United States are being killed such as green ash (Fraxinus pennsylvanica) and white ash (F. americana).

The Significance of Ash

There are approximately 8 billion ash trees in the US, many of which are in natural forests. Estimates of tree mortality from EAB range from the upper 10’s of millions to the low 100 millions. The upper end of that range is similar to estimates for the number of elms lost to the infamous Dutch elm disease, making EAB a pest of historical significance in the United States already.

Ash trees account for a significant proportion of the urban forest in many communities in the US, ironically having been planted to replace the elms lost to DED. They were chosen for their stress tolerance, good growth habits, and relative lack of pest and disease problems. No one saw this problem coming.

At the peak of EAB pressure in a given community, it has proven to be an overwhelming problem, especially in the cities and towns where it showed up first. Early management efforts were modelled after other invasive pest programs in the United States, but virtually all of those were ineffective for EAB. The cash costs for removals alone have stretched and broken municipal budgets to the point that replanting programs have been put on hold in order to alleviate the more immediate problem (i.e. dead trees in the 100’s or 1000’s).

Lessons Learned

With persistence by universities, product manufacturers, municipalities, and private companies several effective management approaches have been developed. Not to say people are “saving all the ash trees”, but rather we have found methods to alleviate some of the pain. New tools like i-Tree have become valuable resources to help municipalities quantify the physical, economic, and social benefit losses attributable to this pest, and to help justify and defend urban forestry budgets. Modelling the benefit losses with i-Tree has also helped communities find new sources of funding for their programs from creative sources.

A pest of historical significance with many lessons learned.

Jim Zwack will speak on Day 1 of Tree Health, Resilience and Sustainability. 

Wingfield Mike 125

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