The Emerald Ash Borer was first discovered in the United States in 2002, and had likely been living here covertly since some time in the 1990s.  It is theorized that the beetle was accidentally brought to the US from Asia in wood packaging and cargo from boats or planes.  The discovery of this invasive species and its deadly consequences to its host trees directed a lot of focus to these beetles in the scientific community, and prompted many studies to learn more about them, and how to properly manage them before the damage becomes catastrophic.  Important focus on Emerald Ash Borer spread, impacts, lifecycles, and management strategies have significantly developed since its discovery in 2002.

 

Emerald Ash Borer is native to countries such as China, Japan, Taiwan, Korea, and some of Russia.  In these countries, the beetle populations are easily suppressed by natural phenomena and evolutionary relationships such as natural predators, parasitoids, and trees with resistance to the beetle invasions.  The difference in ecology in the United States allows for these beetle populations to surge and expand to large infestations only limited by food availability.  With Ash trees being a very common tree to be used in green infrastructure, food sources are vast across the country.  As soon as Emerald Ash Borer’s damage became apparent, strategies to mitigate the spread and destruction across the country began to take shape as well.  Due to this beetle’s large-scale destruction and mappable spread, this particular invasive species has set a lot of litigation, policy, and management practices in the field of invasive mitigation, entomology, ecology, and technology. (Mallet, 2022)

 

One of the first strategies for the mitigation of these invasive insects is tracking and monitoring.  Scientists and managers have detailed some important things to look for when looking for Emerald Ash Borer invasions, allowing for the tracking of the species spread across the country.  Identifying invasions early on is extremely difficult to do, so a lot of studies have been utilized to come up with monitoring plans.  Adult beetles emerge from ash trees between May and September and leave “D” shaped exit holes.  Upon investigation of exit holes, under bark should reveal “S” shaped tunnels from feeding larvae.  Symptoms of living trees stressed by invasions might be dead top branches of trees, epicormic branching, and sizeable woodpecker activity on infected trees.  Leaving strategic pheromone traps to monitor beetle species present is also a good idea.  While these beetles move slowly themselves, due to host tree availability and lack of population control, moving infested firewood can spread this invasive species very quickly. (Cameron, 2020)

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Once an Emerald Ash Borer infestation is identified cutting down infected trees and quarantining the area is the next best step.  Arborists use chainsaws and pruners to remove these dead or infected trees and the wood is either burned or chipped.  Removal of all trees and replacement with other species is standard protocol, replacement tree planting can be done in many different ways, but the use of a tree spade machine is pretty common.  Quarantine of all wood and plants is then placed which makes inspection and treatment necessary before moving out of infected areas.  High-value trees can be targets of insecticide use, however, this is not a feasible management option for large-scale uses on all ash trees in the United States.  Large-scale use of insecticides such as Dinotefuran, Azadirachtin, and Imidacloprid is not viable because it would be extremely expensive to treat all Ash trees in the country and the enormous quantity of insecticides needed would be hard to get and potentially dangerous.  Releasing parasitoid wasps has been attempted as well, but these little insects seem to have difficulty surviving cold winters and establishing populations for long periods of time, and becoming effective management options.  Parasitoid Wasp species that target the Emerald Ash Borer include: Cerceris fumipennis, Beauveria bassiana, Tetrastichus planipennisi, Spathius agrili, and Oobius agrili.  Providing suitable habitats for other natural predators such as native woodpeckers is a helpful management strategy.  The use of resistant strains of trees with higher tannin concentrations makes it harder for the beetles to eat the tree’s wood. Breeding resistant strains of Ash trees ‘naturally’ through selective breeding is done to rebuild populations afterward is viable, but can also risk beetles also gaining resistance eventually as well over time. (Mallet, 2022)

 

The study of entomology, ecology, and forest management was vital when it came to studying the Emerald Ash Borer’s lifecycle, habits, and impacts.  First, knowing how these particular beetles live and reproduce gives scientists the ability to develop management strategies that are effective.  Understanding ecological impacts help these scientists develop techniques that are both efficient and safe for the rest of the biological community.  The use of technology is incredibly important, especially in circumstances such as baited pheromone traps, mapping of infestation spreading, the removal of trees, and more.  Not many infestations have required this amount of funding and attention, therefore the Emerald Ash Borer is both setting the bar and assisting in developing the field of invasive species containment and eradication.