Ash Tree Identification
Leaves are compound; meaning they usually have 5 to 9 leaflets on each stem. Leaves can be confused with walnut, tree of heaven, and hickory, but those trees are far less common around Fort Collins than ash.
White Ash Young white ash trees can have either diamond shaped bark or smoother bark with plates and cracks as in this photo. As the tree matures the trunk takes on the diamond-shaped bark. The color of the bark varies; it can be white, grey, and pink or orange. Autumn Purple ash are a type of white ash and have smooth-barked limbs.
Green Ash tend to have oblong diamond shapes in the bark, and bark tends to be ash grey in color.
Emerald Ash Borer Identification
Epicormic Growth are shoots coming up from low on the trunk and are one indication of Emerald Ash Borer damage.
Woodpecker activity is high in trees with a high population of EAB larvae.
Adult Beetles are only about a half inch long, shiny metallic green and may be found in early summer feeding on ash foliage. (pictured)
Bronze Birch Borer is a close relative of Emerald Ash Borer and exists in the Fort Collins area, and could easily be mistaken for EAB. Probably only an entomologist could tell the difference.
EAB Exit Holes can be found in the trunk and branches of an infested tree. They start higher in the canopy and only show up lower down as the infestation progresses. Holes are shaped like a capital letter D and are quite small.
EAB Damage and Lifecycle
Life Cycle: Adults emerge in May and June and begin feeding on the foliage of ash trees. Females soon begin laying eggs on the bark of ash trees, and the eggs hatch a couple weeks later. Larvae bore into the tree (they are very small so we don’t see these holes) and begin feeding on the nutrient-rich tissue just beneath the bark. The larvae “molt” several times before overwintering in the wood and finish developing in the spring. As the flat-headed larvae chews it’s way out of the tree, it leaves its characteristic D shaped exit hole. At this point the larvae pupates and the adult beetle is formed.
Ash Trees in North America have no resistance to EAB, and so long as the insect’s population is sufficient, all untreated ash trees within an infestation area will eventually die. The process actually takes many years, as many as eight, but visually most of the damage takes place in about two years.
The First Year or two of infestation, the tree may have little or no outside visual symptoms. As things progress, you may notice the canopy of the tree will start to thin. Once the canopy has died back by 40%, treatments are no longer effective, and the tree will likely die within the next year or so. When a tree is heavily infested, there are many other signs as well: Heavy woodpecker activity, suckers growing at the base of the tree, and bark splitting vertically.