Emerald Ash Borer – Agrilus planipennis
Emerald Ash Borer – Agrilus planipennis
Description of Insect:
The emerald ash borer (Agrilus planipennis) is an invasive beetle that has caused devastating losses to ash tree populations. Native to Asia, this metallic green beetle belongs to the Buprestidae family, commonly known as metallic wood-boring beetles. Adults measure about 8.5 mm in length and have an elongated, slender body with a striking emerald green coloration. Underneath their wing covers, they have a coppery-red abdomen, which helps distinguish them from other similar beetles.
While the adult beetles feed on ash leaves, their damage is relatively minor. The real threat comes from their larvae, which tunnel into the tree’s inner bark and disrupt the transport of nutrients and water. The larvae are creamy white and grow up to 32 mm long. As they feed beneath the bark, they create distinctive S-shaped galleries, eventually leading to tree decline and death.
One of the reasons the emerald ash borer is so destructive is its ability to go undetected for years. Infested trees typically die within ten years, making this pest one of the most aggressive tree killers in North America.
Life cycle of Emerald Ash Borer
The emerald ash borer has a one- to two-year life cycle, depending on climate conditions. The cycle begins when adult females lay eggs in the crevices of ash tree bark. Each female can lay between 60 to 70 eggs, which hatch within 17 to 19 days. The newly emerged larvae burrow into the bark and start feeding on the phloem layer. They create winding tunnels that disrupt the tree’s vascular system, lasting approximately 300 days.
The larvae undergo four instars before overwintering inside the tree, either as mature larvae or as pupae. Pupation occurs in the spring, and the adult beetles emerge by boring out of the bark, leaving behind characteristic D-shaped exit holes. The adult beetles are most active in warm months, particularly from May to July when they fly to new ash trees to feed and reproduce.
Damage they cause:
The emerald ash borer has caused severe ecological, economic, and aesthetic damage since its introduction to North America.
- Ecological Impact: Ash trees play a crucial role in forests, wetlands, and urban landscapes, providing habitat and food for many species. The loss of ash trees has disrupted ecosystems by reducing canopy cover, altering soil composition, and negatively affecting wildlife dependent on these trees for shelter. Additionally, the rapid decline of ash trees allows invasive plant species to take over, further altering natural habitats.
- Economic Impact: The emerald ash borer infestation has placed a heavy financial burden on municipalities, homeowners, and industries that rely on ash trees. Local municipalities and homeowners have been forced to remove thousands of dead and dying ash trees to prevent safety hazards such as falling trees. According to an estimate, the cost of tree removal and replacement across 25 states is almost $25 billion, straining local budgets.
- Aesthetic Impact: Ash trees have long been a staple of streetscapes, parks, and residential landscapes. Their graceful, rounded canopy and vibrant fall colors make them a favorite choice for urban planning. However, the emerald ash borer has devastated these landscapes, leaving behind dead and dying trees that must be removed.