The adult emerald ash borer is a dark metallic green beetle with a bullet-shaped, slender body. When wings are spread, the top of the abdomen under the wings is metallic purplish red. Adults are most active during the day, from late May to mid-June.
The larva (immature stage) is flattened, cream-colored, approximately 1 inch long when fully developed.
Signs: Larvae feed under the bark of ash trees, leaving S-shaped galleries. Adults emerge from the tree, leaving D-shaped exit holes that are ⅛ inch in diameter.
Length: to ½ inch; width: to ⅛ inch.
The EAB was discovered in July 2008 in southeast Missouri in a campground at Wappapello Lake. Since then more infestations have been detected, and as of 2020 the insect has become widespread in the state.
Habitat and Conservation
The EAB can infest all types of ash trees. Adults can fly at least ½ mile from their home trees, but many infestations start when people move infested ash wood into uninfested areas. Places infested with EAB are under quarantine. No one may move ash nursery stock, any part of an ash tree, or firewood cut from any hardwood species outside of infested counties and the state.
Adult beetles nibble on ash foliage but cause little damage. The larvae, however, feed on the inner bark of ash trees, disrupting the tree's ability to transport water and nutrients, which eventually kills the tree. All of Missouri’s native ashes can be affected, including green, white, pumpkin, and blue ash. Horticultural cultivars (such as Autumn Purple white ash or Marshall Seedless green ash) can be killed as well. The EAB infests trees ranging from saplings to fully mature specimens.
Invasive. Native to Asia. After its first detection in our state in 2008, additional EAB populations have been detected in several counties across the state. As of 2020, the EAB had become widespread in Missouri. The EAB has been confirmed in many states in the eastern United States and adjacent Canadian provinces.
Usually has a 1-year life cycle. A female can mate numerous times and lay a total of 30-60 eggs before dying at the end of the season. She deposits each egg singly into bark crevices of ash trees. The larvae hatch in 7-10 days, chew through the bark, and feed on phloem and outer sapwood for weeks. In autumn, they stop feeding and overwinter in shallow chambers in outer sapwood or bark. Pupation begins in late March or April. Adults emerge in spring and summer, leaving a D-shaped exit hole.
Left unchecked, the EAB will destroy Missouri’s ashes, ruining millions of dollars in forest products and costing us for dead-tree removal. As the EAB spreads to more states, federal funding for fighting it has almost disappeared, leaving states and municipalities to search elsewhere for funding.
If you have an ash tree that you would like to save, contact a certified arborist about having it treated.
While most native borers kill only severely weakened trees, the EAB kills healthy trees, making it especially devastating. EAB harms American ecosystems by destroying all the ash trees, damaging shade and wildlife habitat. There are few ways to control EAB beyond trying to slow its spread.