The Emerald Ash Borer continues to expand both locally and nationally. Today, the Ohio Department of Agriculture issued a press release announcing the EAB Quarantine was being expanded to 14 additional Ohio counties.
During the 2009 growing season, an alarming increase in the spread of the this ash tree destroying insect was noted in the Cincinnati area. Confirmations of the insect's presence came at a rapid-fire pace, including finds over several square miles of Liberty Township as well as Indian Hill, Terrace Park, Mariemont, Hyde Park, Norwood, Oakley, Over-the Rhine, Clifton, Paddock Hills, Mount Adams, and Covington, KY. Visual evidence that the insect is likely present have been noted over an even much larger portion of the Cincinnati tri-state area.
The Emerald Ash Borer is an exotic insect native to Asia. It was first identified in southeast Michigan in 2002, although it is now believed the insect had been active for 10 years or more before identification. Native ash trees, which make up over 10% of the total tree population in Ohio, have no appreciable resistance to the pest and typically die within five years of infestation. 67 of Ohio's 88 counties are now included in the Ohio Emerald Ash Borer quarantine. The total infestation has spread to 14 U.S. states and Canada.
Protective treatments are available for the protection of individual trees. Over-the-counter formulations of Imidacloprid may not be effective on trees larger than 8 or 10 inches in diameter. Xytect, a new, stronger formulation marketed by Rainbow Tree Care, which must be applied by arborists, can protect trees to 20 inches in diameter. Emamectin benzoate, trade named Tree-age, protects trees of all sizes and lasts for at least two years. This material must be injected into the trunk and is rather pricey.
The city of Cincinnati has elected not to perform protective treatments on ash trees. Instead, the city will be removing and replacing 400 ash trees per year through 2016. The communities of Terrace Park, Wyoming, and Mariemont have also decided to replace ash trees.
Whether or not to treat can be a complicated decision, especially if there are a large number of trees involved. Purdue University has posted a web-based Emerald Ash Borer calculator to aid in calculating costs and making treatment decisions.