Emerald Ash Borer Is Here to Stay. What Property Owners Need to Know Insects, Mites & Diseases What Is the Emerald Ash Borer? The emerald ash borer (Agrilus planipennis), commonly referred to as EAB, has killed hundreds of millions of ash trees across North America and remains one of the most destructive invasive forest insects in U.S. history. The insect attacks trees in the Fraxinus genus, commonly known as true ash trees. It is native to parts of Asia, including China, Japan, Korea, Mongolia, and the Russian Far East. The insect attacks and kills trees in the Fraxinus genus, commonly known as true ash trees. It is important to note that trees with “ash” in their common name but outside the Fraxinus genus — such as mountain ash (Sorbus species) — are not hosts for EAB. Since its accidental introduction to North America, EAB has become one of the most destructive invasive forest insects in U.S. history. EAB larvae feed beneath the bark of ash trees, creating winding galleries that disrupt the tree’s ability to move water and nutrients. Without treatment, infested ash trees typically die within three to five years. Today, EAB is established throughout much of the eastern and central United States, and its range continues to expand. If you have ash trees on your property, working with an experienced ISA Certified Arborist® is one of the most important steps you can take to identify risks early and determine the best strategy to protect valuable trees before severe decline begins. How Emerald Ash Borer Spread Across North America As of 2025, EAB has been detected in 37 states and multiple Canadian provinces. The impact has been severe: Tens of millions of ash trees have been lost in Michigan alone. Hundreds of millions of ash trees have been lost across North America, making the emerald ash borer one of the most destructive invasive forest insects ever introduced to the continent. Municipalities, homeowners, and property managers have spent billions of dollars on treatment, removal, and replacement costs. In some heavily infested forest areas in southeast Michigan, researchers documented mortality rates exceeding 99% among ash trees. Ash trees have historically played an important role in residential landscapes, municipal streetscapes, parks, and forests. Their decline has altered ecosystems, reduced canopy cover, increased removal costs for communities, and created significant safety concerns for property owners. Although the emerald ash borer has been present in many regions for years, some property owners assume the threat will eventually pass. Research and field experience show otherwise. EAB Does Not Disappear One of the most common misconceptions about EAB is that it eventually "goes away." It does not. Once established in an area, EAB populations typically follow a predictable pattern. Populations increase rapidly as large numbers of untreated ash trees become infested and die. After much of the available ash resource is depleted, beetle populations decline, but the insect remains present in the environment. As younger ash trees regenerate or untreated ash trees remain available, EAB populations can rebound. In 2021, the U.S. Department of Agriculture ended the federal domestic quarantine for EAB, acknowledging that eradication is no longer possible. EAB is now considered a permanent invasive insect in affected regions. Property owners sometimes assume that if nearby ash trees have already died, the threat has passed. Unfortunately, that is rarely the case. EAB remains established in affected regions and continues to attack untreated ash trees. Waiting to see what happens can mean losing the opportunity to protect a valuable tree before irreversible decline begins. For your property, this means long-term management is essential if you have ash trees you hope to preserve. Untreated ash trees remain at significant risk of decline and mortality when EAB is active in the surrounding area. Signs EAB May Be Active on Your Property EAB infestations often go unnoticed until trees begin showing visible decline. Common signs include: Thinning or dieback in the upper canopy Bark splitting or peeling S-shaped galleries beneath the bark Small, D-shaped exit holes in the bark Increased woodpecker activity Epicormic sprouting, or new shoots growing from the trunk or lower branches If you notice any of these symptoms on your ash trees, schedule an inspection with your SavATree arborist. Real-World Impact: Lessons From Affected Communities Southeast Michigan: Outbreak Origin The Detroit metropolitan area was the first region in North America to experience widespread devastation from EAB. Within only a few years of discovery, millions of ash trees across neighborhoods, parks, and forests were dead or declining. Ash had become a widely planted urban tree following the loss of American elms to Dutch elm disease. As EAB spread, entire streetscapes and neighborhoods experienced dramatic canopy loss. Researchers studying forests near southeast Michigan found ash mortality rates exceeding 99% in some locations. Even decades after the initial outbreak, EAB remains active in the region. Vermont: Managing a Growing Threat EAB was first confirmed in Vermont in 2018 and has since spread across much of the state. Ash represents a meaningful portion of Vermont’s forest canopy, and some communities face significant canopy loss as EAB populations expand. Municipalities and state agencies have responded with management plans that include: Ash tree inventories Targeted insecticide treatments Removal planning for hazardous trees Biological control programs using parasitoid wasps Vermont has also prioritized protecting black ash (Fraxinus nigra), a species of cultural importance to Wabanaki communities. A Broader Urban Forestry Lesson After Dutch elm disease devastated American elm populations, many municipalities relied heavily on ash trees as replacements. EAB demonstrated the long-term risk of overreliance on any single tree species. Today, urban forestry professionals increasingly emphasize diverse planting strategies to strengthen resilience against future pests and diseases. Reasons for Cautious Optimism Although EAB remains a serious threat, arborists and researchers now have some effective tools to help protect ash trees and manage long-term impacts. While it is a pervasive threat and often doesn’t have a dependable outcome, there are ways to manage if you implement early mitigation. Trunk Injections and Preventive Treatments Systemic treatment programs, particularly those using emamectin benzoate, have proven effective in protecting ash trees when applied according to the recommended treatment schedule. Trees treated before severe infestation can often remain healthy for many years, even in areas with active EAB populations. However, timing matters. Preventive treatment is significantly more effective than waiting until a tree is already in advanced decline. Biological Control Programs Researchers and the USDA have introduced several species of parasitoid wasps from EAB’s native range as part of long-term biological control efforts. These wasps target EAB eggs or larvae and may help reduce overall beetle populations in forested environments over time. Biological controls are not a replacement for the treatment of valuable landscape trees, but they may contribute to long-term suppression of EAB populations. Research Into Resistant Ash Trees Scientists are also studying ash trees that appear to show natural tolerance or resistance to EAB. Although large-scale restoration efforts are still years away, this research provides hope that ash trees may eventually remain part of North American forests and landscapes. What Property Owners Should Do Now If you have ash trees on your property, waiting for visible decline is one of the biggest mistakes you can make. By the time canopy thinning, dieback, and other symptoms become obvious, EAB may have been present for years, reducing treatment success. An experienced ISA Certified Arborist® can help you understand your options by: Confirming whether your trees are ash Evaluating tree health and structural condition Identifying signs of EAB activity Recommending appropriate treatment options Helping you determine whether preservation or removal makes the most sense for the health of your property Not every ash tree can or should be saved, but many healthy, high-value trees can be protected with timely treatment. Waiting until a tree shows severe decline can limit treatment success and increase removal costs and safety risks. The Bottom Line Emerald ash borer continues to change forests and landscapes across North America. The insect is not a temporary issue, and untreated ash trees remain highly vulnerable in affected regions. But with early detection, science-based treatment programs, and guidance from experienced arborists, you can make informed decisions that help preserve valuable trees and reduce long-term risk. If you have ash trees on your property, an evaluation today can help you understand their condition and determine whether treatment is appropriate. At SavATree, our experienced ISA Certified Arborists® help homeowners and property managers assess, monitor, and protect valuable ash trees using proactive, science-based care strategies tailored to each landscape. We care for what you love. Contact us today to schedule a consultation with an expert arborist.