Emerald Ash Borer: A Threat to Pennsylvania’s Ash Trees

Adult EAB are distinguished by their bright metallic green color and are approximately 1/3 of an inch (8.5 mm) long and about 1/16 of an inch (1.6 mm) wide. Females are also slightly larger than males. The elytra (hard shells that serve as protective cases for wings) are typically a darker green but can also have copper hues. Another distinguishing feature of the adult emerald ash borer species is its bright red upper abdomen that can be seen when the wings and elytra spread.

The emerald ash borer has a 1-year life cycle. Adult beetles emerge through D-shaped exit holes in a tree around late May and early June—adult activity peaks between mid-June and early July. After appearing, the adult beetles feed on ash foliage for several days and then begin to mate. Females lay approximately 60-90 eggs in their lifespan, which hatch in 7 to 10 days.

After hatching, the larvae tunnel through the bark into the ash tree’s phloem (plant tissue). Larvae feed on phloem for several weeks, creating S-shaped paths in the tree under the bark. As larvae grow, these galleries become progressively wider. Prepupal larvae overwinter in shallow chambers within the bark. Pupation begins in late April or early May and lasts 1 to 2 weeks when this species’ life cycle starts again.

If you have ash trees on your property, knowing the signs and symptoms of EAB infestation is crucial to keeping them safe and preventing damage. These signs include the following:

• Thinning canopy and dieback of branches
• D-shaped exit holes in the ash tree bark
• S-shaped galleries under the bark
• Increased woodpecker activity (as woodpeckers feed on larvae)

As mentioned above, EAB larvae feed on the nutrient-rich inner phloem, cambium, and outer xylem beneath the bark, creating S-shaped galleries packed with sawdust-like frass. As the infestation of this invasive species progresses, the symptoms mentioned above become more apparent. Trees will die after 3 to 4 years of heavy infestation, making EAB control tactics crucial to preserving ash tree populations.

Prevention is the best way to avoid damage, and there are several steps you can take to protect your ash trees from EAB:

• Do not move firewood: Moving firewood can inadvertently transport EAB to new locations. Some states, including Pennsylvania, have restrictions on moving firewood because of invasive insect species. Always buy firewood locally and burn on-site.
• Use insecticides: Preventive insecticides containing certain ingredients and agents can be applied to healthy ash trees to protect them from EAB. Consult a certified arborist for advice on the appropriate insecticides and application methods.
• Plant diverse tree species: Planting a variety of tree species can help reduce the impact of EAB on your property and promote a healthier ecosystem.

As mentioned above, EAB larvae feed on the nutrient-rich inner phloem, cambium, and outer xylem beneath the bark, creating S-shaped galleries packed with sawdust-like frass. As the infestation of this invasive species progresses, the symptoms mentioned above become more apparent. Trees will die after 3 to 4 years of heavy infestation, making EAB control tactics crucial to preserving ash tree populations.

If your ash trees are already infested with EAB, Burkholder PHC offers various treatment options, including:

• Insecticide: Treatments can be applied to infested trees to kill EAB larvae and prevent further damage. Some application options include soil drenches, soil injections, or stem injections.
• Tree Removal: In some cases, infested trees may need to be removed to prevent the spread of EAB to nearby healthy trees.
• Replacement Planting: After removing infested trees, consider planting a diverse selection of tree species to help restore the ecosystem.