​What’s the Problem with Emerald Ash Borers? 

In 2002, a small, gem-like green beetle was identified in  Michigan and Ontario: the emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae). Experts estimate that EAB first arrived in North America in the mid-to-late 1990s, likely through infested wood packaging materials. (Haack 2015) Since then, EAB has spread to multiple Canadian provinces and 35 U.S. states, killing tens of millions—possibly up to 100 million— ash trees. These beetles feed exclusively on Fraxinus species, the true ash trees native to North America but cultivated worldwide. 

Economic Importance

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Ash trees play crucial ecological and economic roles. They are widely planted in urban areas due to their adaptability, rapid growth, straight form, and ability to tolerate a range of soil conditions. Their relatively low maintenance, good shade coverage, and resistance to pollution have made them a staple in city greening efforts. (Vega et al. 2025) 

 
In addition to their urban importance, ash trees provide valuable lumber. Their lightweight, elastic, and shock-resistant wood is used in millwork, cabinetry, flooring, and furniture. Ash is also prized for sporting equipment such as baseball bats, hockey sticks, and oars. (Sciencing 2025) 

 
Ironically, ash trees were extensively planted in cities after Dutch elm disease nearly wiped out American elms from the 1960s to the 1990s. (Minnesota Department of Agriculture 2025) Now, history is repeating itself, as EAB threatens to devastate urban and natural ash populations. 

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Ecological Importance of Ash Trees 

Beyond urban landscapes, ash trees are vital components of forests, wetlands, and riparian ecosystems. (Minnesota Department of Natural Resources 2025) They thrive in transitional zones, such as the edges of woodlands and watersheds, where they help regulate water levels and prevent erosion. In wetland environments, species like black ash (Fraxinus nigra) are often the only trees capable of surviving in saturated soils. (USDA Forest Service 2025) These trees also provide critical habitat. For example, the winter wren (Troglodytes hiemalis) has been found to favor ash swamp areas exclusively. Other species rely on ash trees for shelter, nesting, and foraging. (USDA Forest Service 2025) 

The large-scale loss of ash trees threatens these ecosystems, potentially disrupting entire food webs and altering hydrological cycles. Ash trees play a particularly important role in wetland ecosystems, where they help control water levels. They actively absorb large amounts of water from the soil, effectively lowering the water table and preventing wetland expansion. This function is critical in areas where black ash dominates, as it acts as a natural regulator of moisture levels. (Northeast Climate Adaptation Science Center 2025) 

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The Impact of EAB on Natural Resource Management 
EAB infestation presents a significant challenge to natural resource professionals, as it leads to widespread tree mortality, habitat loss, and ecological imbalance. Unlike natural disturbances, EAB prevents ash trees from regenerating, further accelerating their decline. (Minnesota Department of Natural Resources 2025) 

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How Does EAB Kill Ash Trees?

 
Female EABs lay eggs in the cracks and crevices of ash tree bark. Once hatched, the larvae burrow into the tree, feeding on the vascular system (xylem and phloem) that transports water and nutrients. As they tunnel in an S-shaped pattern beneath the bark, they effectively cut off the tree’s ability to sustain itself. The first visible signs of infestation include canopy dieback and the death of smaller branches at the tree’s extremities. (Government of Manitoba 2025) 

 
During the winter, larvae remain inside the tree and pupate. By April, adult beetles emerge by boring through the bark. Infested trees often lose large swaths of bark, giving them a shaved appearance. After multiple infestation cycles, entire sections of the trunk may be exposed, making the tree more susceptible to secondary infections and infestations. 

Although adult EABs rarely travel more than a mile from their emergence site, human activity has significantly contributed to their spread, primarily through the transportation of firewood and infested lumber. (Nebraska Department of Agriculture 2017) ​