Emerald Ash Borer Found in Colorado - How to Treat Your Ash Tree
EAB is considered the most destructive forest pest ever seen in North America. It is responsible for killing more than 50 million ash trees in over 20 states. Just in the Denver area alone, there are 1.45 million ash trees at risk. If you have an ash tree, there are preventative measures you can take.
To mitigate the damage to Colorado trees, Swingle strongly advises the following actions and services for homeowners and property managers:
- First, consult an expert, such as a Swingle Landscape Care Consultant, to verify ash tree inventory, evaluate the trees for infestation and make custom recommendations.
- Do not plant new ash trees. Good substitutes for ash include maples, lindens, honeylocusts, hackberrys, oaks and elms.
- Do not move firewood made from ash trees out of the area.
- Prune dead branches. Dead branches weaken the tree; an unhealthy tree is much less likely to survive an Emerald Ash Borer attack. This activity is also timely as we move deeper into autumn, as dead branches on trees are a risk of breakage should we experience early winter storms on Colorado’s Front Range.
- A likely prescription from an arborist is a trunk injection, to be completed in the spring of 2014, within a 15-mile radius of any detected emerald ash borer infestation. At present, this includes communities in Boulder, Lyons, Longmont, Niwot, Erie, Lafayette, Superior, Broomfield, Westminster and Nederland. More immediately, Swingle recommends a soil injection, to be completed in the autumn of 2013, outside any 15-mile detection area.
- Additional recommendations may include tree fertilization and lilac/ash borer or ash bark beetle spray.
Ash trees are identifiable by compound leaves with five to eleven leaflets and branches and buds in pairs directly across from each other (opposite branching). The bark of mature ash trees has diamond-shaped ridges.
Initial detection of Emerald Ash Borer in ash trees is difficult. Signs of infestation include:
- Canopy dieback, beginning at the top of the tree and progressing downward
- In later stages of infestations, ash trees may form sprouts from the trunk and roots.
- Bark can split, exposing “S”-shaped galleries underneath.
- Adult beetles leave a “D”-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge.
- Woodpecker activity and damage increases where they are trying to get to the larvae in the tree.
It may take up to five years for the canopy of an infested ash to thin and decline. Since borers infest the upper branches of the tree, the “D”-shaped holes cannot be seen from the ground until the tree is severely infested.
Where did the emerald ash borer come from?
Emerald ash borer (Agrilus planipennis), was introduced accidently into Michigan in wood packing material imported from eastern Asia sometime in the 1990’s. It became well established in Michigan until ash trees started dying in 2002, when it was first detected. It is responsible for the deaths of millions of ash trees in the Midwest and eastern U.S.
How long has the emerald ash borer been in Colorado?
The emerald ash borer was first detected in Boulder, CO. on September 23rd, 2013. It was confirmed on September 26th, 2013. At this time, it has not been found anywhere else in the state. According to the Department of Agriculture, it may have been here approximately 3 years.
What type of trees does the emerald ash borer attack?
All species of the North American ash (Fraxinus sp.) are susceptible. Mountain ash (Sorbus sp.) IS NOT included.
What happens to infested ash trees?
Signs of infestation include:
1. Canopy dieback beginning at the top of the tree progressing downward until the tree is bare.
2. In later stages of infestations, ash trees may form sprouts from the trunk and roots.
3. Bark can split, exposing “S”-shaped galleries underneath.
4. Although difficult to see, the adult beetles leave a “D”-shaped exit hole in the bark, roughly 1/8 inch in diameter, when they emerge.
5. Woodpecker activity and damage increases where they are trying to get to the larvae in the tree.
What do emerald ash borers look like?
Emerald ash borers are a bright, metallic-green color. They are approximately ½” long and have a flattened back. They can be mistaken for other green insects, so a positive identification by a professional is necessary.
What is the life cycle of this borer?
Adults emerge between mid-May through late July, when they feed on ash leaves. They mate, and then females lay eggs (average of 60-90 per female) in bark cracks. Larvae hatch from the eggs within one week and then bore through the bark and into the cambium. Larvae feed under ash tree bark from mid-summer through the next spring, producing the “S”-shaped tunnels. They pupate in the spring and the new generation of adults emerges shortly thereafter.
How is this pest spread?
The EAB adult flies ½ - 1 mile a year. However, borers can also be spread via firewood from infested trees. DO NOT move ash firewood from ash trees out of the area.
Does it only attack dying or stressed trees?
Whereas other boring insects prey upon stressed or weakened trees, emerald ash borer successfully attack all ash in its wake.
How big of problem is EAB?
EAB is now considered the most destructive forest pest ever seen in North America. Just in the Denver area, there are 1.45 million ash trees at risk.
How do I know if I have an ash tree?
We recommend a Landscape Care Consultant visit your property to verify your ash tree inventory. However, ash trees have:
1. Compound leaves with 5 to 11 leaflets
2. Branches and buds are in pairs directly across from each other (opposite branching)
3. Mature bark has diamond-shaped ridges
How do I know if my tree is infested with emerald ash borer?
Initial detection is not easy. It may take 4-5 years for the canopy of an infested ash to thin and decline. Since borers infest the upper branches of the tree, the “D”-shaped holes cannot be seen from the ground until the tree is severely infested. We recommend a Landscape Care Consultant visit to evaluate your tree and we’ll make recommendations at that time.
What is Swingle recommending for treatment options to protect my ash tree?
1. Within 15 miles of a detected emerald ash borer infestation, we are recommending a trunk injection completed in the spring. Includes zip codes:
80005, 80007, 80020, 80021, 80025, 80026, 80027, 80028, 80038, 80301, 80302, 80303, 80304, 80306, 80307, 80308, 80309, 80310, 80314, 80321, 80322, 80323, 80328, 80329, 80403, 80455, 80466, 80471, 80481, 80501, 80502, 80503, 80533, 80540, 80544
Includes Boulder, Lyons, Longmont, Niwot, Erie, Lafayette, Superior, Broomfield, Westminster, Nederland
2. Outside of the 15 mile detection area, we are recommending a soil injection to be completed this fall. We will recommend a soil injection beginning in the spring.
What other recommendations would Swingle have for my ash tree?
We would like to set up a visit for your Landscape Care Consultant to evaluate your ash trees and make recommendations based on your trees current condition. They may recommend the following:
2. Tree Fertilization
3. Lilac/Ash Borer or Ash Bark Beetle spray
Does lilac/ash borer spray or ash bark beetle spray treat for EAB?
No, those borers feed in the tree differently and have a different life cycle from the emerald ash borer. The spray control is not effective for the EAB.
If I treat my ash tree for EAB, do I need the sprays for lilac/ash borer or ash bark beetle?
The trunk injection for EAB will also control lilac/ash borer and ash bark beetle.