Ash borers During early stages of infestation, the initial damage is low. However, after two to three years of continuous infestation, there's a substantial growth in the population, which disrupts the tree's nutrient and water transport system, resulting in wilting and eventual tree mortality. With favorable hot and dry climates, populations can kill healthy trees quickly. After one to two years of infestation, the bark often falls off, exposing the tunnel-ridden sapwood. They cause D-shaped exit holes along the lower bole surface with frass, filled, zigzagging tunnels are indications of A. planipennis. Within 1/3 to 1/2 of branches dye within the first year, exhibiting a top-down die-back, with the rest of the canopy dying the following year.
The adult emerald ash borer is 8.5- 14 mm. long and 3.1-3.4 mm. wide. Their bodies are narrow, elongate and cuniform in a metallic blue-green colour. Mature larvae are 26-32 mm. long and creamy white in color. The larva's head is flat and the vertex is shield-shaped. Compound eyes are kidney shaped and somewhat bronze coloured. Eggs of the emerald ash borer are light yellow and turn brownish yellow before hatching. These oval eggs have a slightly convex center.A. planipennis feeding.
Adults emerge from mid May to early June, depending on conditions. They live for around 3 to 6 weeks, feeding on ash foliage for 5 to 7 days before mating. Eggs are laid in bark crevices or under bark flaps, and hatch in seven to nine days. Growing larvae form flat, wide, zig-zagging tunnels as they feed.
Ash borers attack ash trees in the genus Fraxinus, which includes all North American ash species including white ash, green ash, black ash, blue ash, and pumpkin ash. Attacks on non-ash trees have been a concern, but have not been observed in North America to date.