Emerald Ash Borer Update

Emerald Ash Borer Update

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Top:  Serpentine galleries under vertical bark splits are characteristic of emerald ash borer (EAB) larval feeding

Bottom:  Thinning in the upper canopy of ash trees is an early sign of EAB infestation.

You may remember reading about the exotic invasive beetle, emerald ash borer (EAB), in the Winter 2014 edition of Utah Pests News.  At that time Agrilus planipennis had just been discovered killing trees in Boulder, Colorado.  It is now known to occur in 24 states and has been declared “the most destructive forest pest ever found in North America”.  Just this year, it has also been found to be widely distributed in Georgia and Arkansas. 

EAB is virtually 100% fatal to all species of native North American ash trees (Fraxinus spp.).  It is estimated to have killed over 50 million trees and is rapidly expanding its range.  Unfortunately, it is very difficult to detect before it becomes well established and begins causing tree mortality.

Many state and federal agencies, including the Utah Department of Agriculture, USU Extension, USDA Animal and Plant Health Inspection Service, and State Lands and Forestry,  have recently joined forces to form an EAB Outreach Committee to get the word out about the threat to our ash resources.  While Utah does not have a native ash component to our forested areas (other than the small shrubby singleleaf ash–Fraxinus anomala–that occurs sporadically in southern Utah and velvet ash–Fraxinus velutina–in SW canyons), various planted ash species make up a substantial component of our urban forests throughout the state.  Ash comprises up to 30% of the urban canopy in many Utah communities.

When EAB was first discovered in the U.S. in 2002, killing trees near Detroit, Michigan, there was not much known about this insect.  Tree mortality occurred so quickly (within 3 to 5 years of infestation) that it was difficult and costly to conduct timely removal of the hazardous dead trees.  The spread of EAB to additional urban and suburban areas over the next 10 years is projected to cost $10 billion or more for tree removal and replacement or chemical treatments.

Since EAB’s arrival to North America, we have learned a lot and there are now many tools available to help owners of ash trees make management decisions.  One of the most important things that we can all do now before the arrival of EAB in Utah is to educate ourselves about the impacts and management options. 

Some of the things that we can do now to minimize the impacts of EAB include:

  1. Inventory and assess tree health to develop a management plan for when EAB arrives.  Emeraldashborer.info is the best resource for finding cost calculators, decision making tools, latest research, insecticide options, and more.
  2. Do not include ash in any new plantings.  Remove any ash that is not in optimal health or in poor sites.  Treebrowser.org can be used to select ash alternatives and has been updated to include notes about EAB.
  3. Be aware of the signs and symptoms of EAB infestation.  For more details see the USU Extension Fact Sheet on EAB.  The earlier we can detect it the more management options will be available to us.
  4. Be aware of established pests that can be confused with EAB in ash trees, such as the lilac-ash borer (see fact sheet here).
  5. Report anything suspicious to the appropriate people found on this webpage.
  6. Don’t move firewood from EAB quarantined states to Utah.  Burn it where you buy it.  Dontmovefirewood.org contains a variety of outreach materials.

There are some insecticide treatments available to protect higher value trees.  They are not effective once EAB has become established in a tree.  These include soil drenches that can be used by homeowners and systemic trunk injections that must be performed by commercial applicators.  Treatments may need to be repeated annually to protect trees during potential EAB invasions.

USDA has also been working to develop biological control agents to help slow down the EAB.  Utah has applied for permits to release the tiny stingless parasitoid wasps once EAB arrives here.  Stay tuned for more information about biocontrol in the next edition of Utah Pest News.