The Emerald Ash Borer (EAB) is an exotic Asian insect pest whose presence has been confirmed in Illinois, Indiana, Maryland, Michigan and Ohio. Infested trees have been found in urban areas, woodlots and nursery stock. This borer has killed millions of trees, from small, young specimens tto established, mature specimens.
HOSTS: In the United States, the borer has been detected on all species of ash trees.
IDENTIFICATION AND LIFE CYCLE: The adult beetle is elongate, metallic green and 3/8 inch to 5/8 inch long. Adults emerge from late May until early August, feeding on small amounts of foliage that cause jagged leaf edges. Females lay eggs deep into the bark crevices and lower main branches. After the eggs hatch, the larvae tunnel though the bark and feed on the phloem and outer sapwood for several months. Their galleries injure the phloem and xylem that makes up the plant’s circulatory system. The mature larvae are cream colored and are 1 inch to 3 inches long. Fully-grown larvae over winter under the bark or in pupal cells made of outer sapwood. There is one generation per year, but some live larvae can remain in the tree for up to two years.
SYMPTOMS AND SIGNS: Initial symptoms include yellowing and/or thinning of the foliage and longitudinal bark splitting. Along with suckering along the main bark, the canopy may die back, or symptoms may be restricted EAB_damage_3to certain branches. Removal of bark reveals tissue callusing and frass-filled, snake-like tunneling. Tunneling may occur from upper branches to the truck and root flare. Adults exit from the trunk and branch in a characteristic D-shaped exit hole about 1/8 inch in diameter. The intense tunneling causes the trees to lose between 30% and 50% of their canopies during the first year of infestation. Trees often die within two years following infestation.
MANAGEMENT: Removal of infested trees with over 50% of canopy loss is recommended and stumps should be ground out. Quarantines have been set up to prevent movement of untreated ash lumber, firewood or nursery stock from the affected areas. Having a healthy ash tree is the most important step in the control of EAB. A strong tree can recover from a light infestation and be able to absorb the treatments effectively.