Tree identification the key to emerald ash borer prevention in Vail Valley
July 16, 2017
How do I know if I have an ash tree?
All true ash trees (Fraxinus spp.) have the following characteristics:
• Leaves are compound, which means multiple leaflets occur on a common stalk, and typically have five to nine leaflets. The one exception is single-leaf ash (Fraxinus
anomala), which may have simple or compound leaves, with up to five leaflets.
• Leaflets are smooth or finely toothed along the edges.
• Seeds on female trees are paddle-shaped.
• Branches and buds grow in pairs, directly opposite from each other.
• Mature bark displays diamond-shaped ridges.
A video and image gallery showing how to identify ash trees is available at
Source: Colorado Department of Agriculture
For many Coloradans, the word "beetle" sets off an alarm in our heads — we are all too familiar with the massive destruction caused by these tiny creatures.
The state is still feeling the devastating effects of the mountain pine beetle infestation, which reached epidemic levels in 2015, and now, another kind of beetle is arising as a threat to Colorado urban forests — the emerald ash borer.
According to the Colorado Department of Agriculture, the emerald ash borer is an invasive, wood-boring beetle originating from China and Eastern Asia, most likely brought to North America via wood packing materials used in shipping, and it specifically attacks ash trees.
Like the mountain pine beetle, the emerald ash borer lays its eggs under the bark. Once a tree is inhabited, the larvae strip the inner bark away, cutting off the flow of water and nutrients to the tree. The emerald ash borer is an aggressive insect that can kill a healthy tree within two to four years of infestation.
Unlike the mountain pine beetle, the emerald ash borer is not native to Colorado, nor is its target tree species. This is good news for the Vail Valley, as ash trees do not grow naturally in the mountains, but Colorado Department of Agriculture Phytosanitary Manager Laura Pottorff said the emerald ash borer has become a huge problem on the Front Range. Pottorff explained that the ash tree was originally introduced to Colorado because it was so sturdy and tough and did well at high elevations.
"This particular tree was widely available and a good choice for our harsh climate, and subsequently, we used it too much," Pottorff said.
The ash, commonly found in the Midwest, currently makes up approximately 15 percent of trees in Colorado urban forests; the Colorado Department of Agriculture estimates there are around 98,000 ash trees in Boulder County alone and around 1.45 million in the Denver Metro area.
Pottorff warned, however, that though ash trees do not grow naturally in mountain areas, plenty have been planted, and it's important for people to identify their trees in case they are at risk. She said that while the Colorado Department of Agriculture has precautions set in place to protect ash trees, the system is not foolproof.
"A quarantine is in place in Boulder County and surrounding areas to try and prevent the human-assisted spread of (emerald ash borer)," she said.
This quarantine includes the regulation of ash logs, branches and chips, green lumber, all hardwood firewood or any other article that may present a risk of spreading the emerald ash borer. There is careful monitoring of any wood product leaving the Front Range in an attempt to impede the movement of the insect into other areas of the state.
Protecting your trees
Pottorff said these initiatives put in place by the Colorado Department of Agriculture may slow the pest but are unlikely to stop it completely. She explained that the question of whether the beetle will spread to the high country depends on how many ash trees are planted in communities such as Vail.
"The most important thing for property owners to do," Pottorff said, "is to identify the trees on their property. If the trees are native, then they are not ash. If a tree was purchased from a nursery and planted, then ID is necessary."
Few nurseries currently sell ash trees, for fear of spreading the emerald ash borer, but if the tree was planted before the recent infestation concern, it is advisable to identify and check the tree.
If you do own an ash tree, Pottoroff said there are many ways to protect your tree, such as effective insecticides and other management strategies including monitoring trees for the presence of emerald ash borer, removing and/or replacing ash trees and planting new trees nearby in an effort to get them established before the arrival of the insect.
Additionally, there is a free emerald ash borer/ash tree identification app called EAB/Ash Tree ID, available for both iPhone and Android, which can help you identify an ash tree, as well as the emerald ash borer itself. Currently, the emerald ash borer has stayed clear of the Vail Valley, but precaution is an essential step toward prevention and the key to keeping a big beetle problem at bay.