What is an emerald ash borer?
The emerald ash borer is an invasive metallic green beetle from Asia that feeds under the bark of ash trees, blocking water and nutrient transport and killing the tree within 3-5 years of infestation.
An invasive beetle native to Asia, the emerald ash borer has devastated ash tree populations across Connecticut and much of North America since arriving in the early 2000s. The shiny green insect is roughly half an inch long and lays eggs in crevices on ash tree bark. When the larvae hatch, they tunnel under the bark and feed on the tree's phloem and xylem, the tissues that transport water and nutrients. This feeding destroys the tree's circulatory system, causing crown dieback and eventual death, typically within 3 to 5 years of initial infestation.
Property owners and landscapers identify infested ash trees by watching for specific signs: D-shaped exit holes about 1/8 inch wide left when adult beetles emerge, vertical splits and peeling bark where tunnels have created canals beneath the surface, and thinning or dying upper limbs while lower branches remain green. Once an ash tree shows heavy infestation, it is essentially irreversible without professional intervention early in the process.
Because the emerald ash borer kills ash trees at such a high rate and has no natural predators in Connecticut, infected trees often require removal to prevent the pest from spreading to nearby ash trees on adjacent properties. Some property owners opt for insecticide trunk treatments on valuable ash trees caught at earlier stages of infestation. Consulting a tree-service provider experienced with emerald ash borer identification and management helps determine whether removal, treatment, or monitoring is the right choice for a specific tree and property.