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Monday, September 30, 2013

Kiss Your Ashes Goodbye?

My heart broke when I heard that the Emerald Ash borer had been detected in Colorado.  The September 23rd siting in Boulder County, Colorado marks the western-most siting of this game-changing pest.

Emerald ash borer, often abbreviated as EAB by those unlucky enough to be familiar with the pest, feeds on any and all species of North American ash (Fraxinus species).  Trees at risk include the beautiful Oregon Ash (Fraxinus latifolia).

Oregon Ash (Fraxinus latifolia) is an important tree in urban and suburban landscapes, as well as an important native tree in riparian areas up and down the Willamette Valley.
The adult beetles nibble on ash foliage but cause little damage. However, the larvae (the immature stage) feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients.   Once infested, the tree canopy begins to thin.  Heavily infested trees show canopy die-back, usually starting at the top of the tree.  In one year, 1/3-1/2 of all tree branches may die, and most of the canopy can die back within 2 years.  Since first detected in Michigan in 2002, EAB has killed an estimated 50 million ash trees.
The canopy of infested trees begins to thin above infested portions of the trunk and major branches because the borer destroys the water and nutrient conducting tissues under the bark. Heavily infested trees exhibit canopy die-back usually starting at the top of the tree. One-third to one-half of the branches may die in one year. Most of the canopy will be dead within 2 years of when symptoms are first observed. Sometimes ash trees push out sprouts from the trunk after the upper portions of the tree dies. Although difficult to see, the adult beetles leave a "D"-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge in June. - See more at: http://www.emeraldashborer.info/faq.cfm#q
The canopy of infested trees begins to thin above infested portions of the trunk and major branches because the borer destroys the water and nutrient conducting tissues under the bark. Heavily infested trees exhibit canopy die-back usually starting at the top of the tree. One-third to one-half of the branches may die in one year. Most of the canopy will be dead within 2 years of when symptoms are first observed. Sometimes ash trees push out sprouts from the trunk after the upper portions of the tree dies. Although difficult to see, the adult beetles leave a "D"-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge in June. - See more at: http://www.emeraldashborer.info/faq.cfm#q3

Prior to the Colorado siting, EAB sitings have been restricted to East of the Rocky Mountains.  

Emerald Ash Borer Distribution Map, December, 2012.  Red dots are sites of initial detection.  White areas on the map are areas of general infestation.  Map source: http://www.emeraldashborer.info/surveyinfo.cfm. 
Now that EAB has crossed the great barrier of the Rocky Mountains, it is likely only a matter of time until the beetle reaches Oregon.  EAB adults can fly at least a 1/2 mile from the tree where they emerge.  However, most infestations are likely the result of people moving firewood, people moving nursery trees, or people moving logs from an infested area to an uninfested area.

If EAB makes it to Oregon, large expanses of native ash are at risk.  In fact, I overheard one city arborist talk about how he's stopped using ash as street trees, because 'it's not a matter of if, it's a matter of when emerald ash borer arrives'.  This was 3 years ago.
Areas at risk of Emerald Ash Borer Infestation.  Note the predominance of red and yellow up and down the Willamette Valley in Oregon.  Map source: http://www.fs.fed.us/foresthealth/technology/invasives_agrilusplanipennis_riskmaps.shtml
If EAB arrives in Oregon, street trees will suffer.

Emerald ash borer damage (David Cappaert, Michigan State University, Bugwood.org.

But most heartbreaking of all, Oregon Ash in riparian forests may perish.

Image Credit:  http://oregonexplorer.info/wetlands/ForestedWetlands

What can you do to help stem the spread of EAB?  At this point, when EAB has not yet been confirmed in Oregon, the most important thing you can do is to be aware of this pest ~ so that you can be a first responder to an invasive pest.

  1. Familiarize yourself with the signs and symptoms of EAB.  Good resources are listed, below.
  2. If you suspect that you may have EAB in ash, report your finding to the Oregon Invasive Species hotline.  If you want confirmation on a suspected EAB beetle, you can always take it to your local OSU Extension office.   




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