It’s like the children’s book, “The Very Hungry Caterpillar,” but with a bad ending because of a beetle.
The emerald ash borer is lovely to look at with its green and bronze body, but its habit of devouring ash trees by the millions is cause for safety concern here in Fairfax and other counties nationwide.
“It’s unfortunate but true that every ash tree in Fairfax County is infested with emerald ash borer. We just can’t see it yet,” said Charles Layton of our Forest Pest Management Branch, Urban Forest Management Division. “This is a rapidly advancing tree mortality and safety issue for property owners in the county. There is a very small window of opportunity for treatment.”
The emerald ash borer is an exotic, one-half inch long, very hungry beetle (Agrilus planipennis Fairmaire) that was brought into this country most likely on solid wood packing material carried in cargo ships or airplanes from Asia. The pest was first spotted in the United States in Michigan in 2002; 22 additional states are infested now, according to the Emerald Ash Borer Information Network. Since its detection in 2002, the borer has killed millions of ash trees in the United States. Quarantines and fines are in place to prevent the spread of this beetle, but its cryptic nature makes containment difficult. The cost to municipalities and property owners is estimated in the hundreds of millions of dollars. The environmental cost is incalculable.
The emerald ash borer attacks ash trees (and white fringetrees, Chionanthus virginicus, a close relative of the ash tree), but it isn’t the beetle itself that does the damage; the EAB larvae are the responsible critters. In their immature stage, “the larvae feed on the inner bark, disrupting the tree’s ability to transport water and nutrients,” according to the Emerald Ash Borer Information Network. Usually, the tree dies within three years of the initial infestation and its limbs may fall without warning, injuring people and damaging property.
“There is a safety concern because when ash trees or branches die, the wood rapidly becomes very brittle,” said Rachel Griesmer-Zakhar, one of our urban foresters. “The branches, which may look sound, can fall unexpectedly and can easily injure a person or pet, or damage a home or vehicle.
“The best diagnostic features to spot signs are dead branches and splitting bark in the canopy of an ash tree,” Griesmer-Zakhar said. “And look for woodpecker activity. Woodpeckers eat the larvae and pupae under the bark of an infested tree,” she said. When feeding, woodpeckers chip away at the outer bark exposing lighter-colored areas of the inner bark. This phenomenon, called woodpecker blonding, is another reliable indicator that the tree is infested. Finally, look for physical signs of the beetle: ‘S’ shaped, serpentine larval galleries and ‘D’ shaped exit holes in the bark of the ash tree.
Our staff may be able to identify ash trees if you email a detailed picture that shows twigs, bark and leaves to firstname.lastname@example.org. You can also contact our Urban Forester of the Day at 703-324-1770, TTY 711, for advice.
Our urban foresters provide information and advice to homeowners who have ash trees on their property, and they give presentations to organizations such as homeowner or community associations or garden clubs.
“Ash trees may be difficult to identify accurately,” Layton said. “You should hire a professional tree care specialist, or contact us.” These two presentations contain many details you will need to identify, treat or remove an ash tree:
There are several recommended steps for you to take if you suspect an infestation:
- Decide, with the help of a professional tree care specialist, if the ash tree is healthy enough for treatment. Treatment can be effective, if no more than 30 to 50 percent of the branches are dead.
- Obtain two or three estimates from tree care specialists or a certified arborist.
- Find a certified arborist through the International Society of Arboriculture.
- Ensure that professional treatment is applied by certified pesticide applicators.
- Hire a professional to remove ash trees that cannot be saved.
- Plant diverse, native species in place of the missing ash trees.
“First, last and always hire a professional tree care specialist,” Griesmer-Zakhar said. “Roving ‘wood chucks‘ who knock on homeowners’ doors are not licensed or certified to care for trees and may cause more harm than good.”