Emerald ash borer biology and background
An emerald ash borer larva (David Cappaert,
Michigan State University, Bugwood.org).
Focus on the emerald ash borer has sharpened recently, with its discovery in St. Paul in 2009. The non-native insect, which feeds solely on ash trees, was also found in Minneapolis in 2010. Since being detected in Michigan in 2002, it has killed over 25 million ash trees across the country. It was brought over from Asia in packing material that contained ash wood and is thought to have arrived in the early 1990s.
The damaging agent is the immature stage—the larvae—of the insect. In the larval stage, emerald ash borer feeds on the living tissue under the bark of all species of ash trees—to the point that it disrupts the tree’s ability to draw water and nutrients from the soil, eventually killing the tree.
Life cycle of emerald ash borer
The life cycle of emerald ash borer begins when an adult lays eggs in the bark crevices of ash trees. Hatched larvae burrow into the wood and begin to feed, creating an S-shaped gallery under the bark. In Minnesota, larvae typically over-winter for 1–2 years before hatching out in early summer. When they do, they leave D-shaped exit holes in the bark as they emerge. The adult beetles feed minimally on ash leaves and have a natural traveling distance of 0.5–2 miles before they mate and die. Human spread of firewood accelerates the movement of this pest to new areas much faster.
Signs and symptoms
Epicormic shoots
(Edward Czerwinski,
Ontario Ministry of
Natural Resources,
Bugwood.org).
An emerald ash borer infestation is extremely difficult to detect early. It may take 3–5 years for emerald ash borer larvae damage to visibly impact the tree’s health.
Signs that indicate an emerald ash borer infestation include: increased woodpecker activity on living branches, epicormic shoots (sprouts from the trunk and roots), bark splitting and canopy dieback.
Additional information
For more information, visit:
Jim Tresouthick, Village of Homewood, Bugwood.org).
