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PLANT HEALTH CARE Emerald Ash Borer: 2003 vs. 2013 How has our understanding and management of EAB changed in the past 10 years? By Brandon M. Gallagher Watson merald ash borer draws frequent comparisons but, unlike elms in 1920s Europe, it was pretty apparto Dutch elm disease. In many respects, they ent what was killing these ash trees. One peek under are similar. Both are fatal conditions, both are the bark, and researchers could see the culprit was an caused by an exotic agent, and both affect a insect.A little comparative anatomy, and they realized prominent species in the urban forest.When this insect — although not from around here — was Dutch elm disease was first identified in the United States, related to pests we were familiar with managing.The it was 1928.Ten years after its discovery, the science and pest was identified as Agrilus plannipenis, a flatheaded the management plans were still very rudimentary. It beetle known as emerald ash borer.Cousins of this insect, wouldn't be until the 1980s — more than 50 years after the bronze birch borer (Agrilus anxius) and two-lined the first elm was found dead — when a predictable manchestnut borer (A.bilineatus) were well known to arborists agement protocol was finally developed. as pests of birch and oak trees. Unlike these native pests, We are just past the 10-year mark since the discovwhich tend to be secondary pests that attack only stressery of emerald ash borer (EAB); so where are we at? weakened trees, EAB was taking out any ash tree in What has changed in the past 10 years in terms of our Ten years since the discovery of sight, regardless of health. By the time it was discovered, emerald ash borer (EAB); where are understanding the insect, the management tools arborists we at? EAB had been in Michigan for several years and thouhave available to them, and the public perception of Photo courtesy of Rainbow Treecare sands of trees were standing dead or dying. this problem? Responding fairly quickly, USDA-APHIS impleScientific Advancements When Dutch elm disease reached North America, mented quarantines on the movement of ash trees and the fungus had been killing elms in Europe for more than 20 years.There raw ash wood.At this time, they also began partnering with universities was some knowledge at this point that the trees were dying from a fun- such as Michigan State and Ohio State to develop a management protogus — not a reaction to wartime chemicals, as originally thought.There col and evaluate possible treatment options. Research would also focus was also some knowledge that bark beetles were vectoring the disease, on the biology of the insect, understanding the damage potential of this but, beyond that, there was still plenty unknown. For nearly 40 years, pest, and going over to Asia to understand EAB in its native ecosystem. management efforts would focus on trying to stop the beetles.This plan Within just a few years of discovery,EAB was one of the better-understood did little to slow the nationwide spread of the disease, and spraying DDT invasive pests, certainly better understood than Dutch elm disease was from helicopters likely contributed to the misuse of insecticides in the shortly after its discovery.According to Dr. Dan Herms, one of the first mid-20th Century. In fairness to those attempting to manage Dutch elm scientists contacted to research emerald ash borer, an accelerated sciendisease at that time, what else could they do? Vascular wilt diseases were tific understanding of EAB was possible due to greater background poorly understood, and fungicides at the time were often metal-based knowledge of similar pests, a greater number of entomologists available, and formulated for foliar spraying only. Even if injectable fungicides were a greater understanding of management tools, as well as a significantly available, there was no application technology to predictably inject the higher scientific capacity than we had in the 1920s. treatments into the trees. It would be decades and millions of dead trees After the quarantines were established, they were almost immediately before technology caught up with the problem. violated,and infested nursery stock was shipped from Michigan to Maryland Fast forward to 2002.Ash trees in southeast Michigan were dying; and Virginia.Although the beetles are capable of flying on their own to a E 8 Arbor Age / April 2013 www.arborage.com