EAB: What You Can Do
Management options for homeowners
The most important action homeowners all over Colorado can take now is to determine if they have ash trees.
Homeowners who have ash trees and live near areas where emerald ash borer (EAB) is present should consider options for managing their ash. The closer ash trees are to areas of known EAB infestations, the higher the risk they will become infested by EAB through natural spread.
The best management option to address EAB depends on the value of each ash tree to a homeowner, the overall health of the tree and the costs associated with each option.
Know the signs of EAB infestation
Homeowners should monitor their ash trees for the presence of EAB. However, it can be difficult to determine if an ash tree in poor health is impacted by EAB or another issue.
Other insects may infest ash trees in Colorado. These pests are commonly mistaken for EAB. Identification of the pest is critical, since EAB and other pests require different management strategies.
The following are signs of an EAB infestation:
- Sparse leaves or branches in the upper part of the tree
- New sprouts on the lower trunk or lower branches
- Increased woodpecker activity, including flecking where they may expose the lighter inner bark
- Vertical splits in the bark
- D-shaped exit holes approximately 1/8-inch wide, found on the trunk or branches larger than 1 inch in diameter
- Winding, S-shaped tunnels under the bark
Ash tree removal
Trees killed by EAB will need to be removed at some point, but homeowners who are concerned about potential infestation may elect to remove dying or even healthy trees to allow replanting or prevent hazardous conditions. Homeowners should weigh the costs of removal against the costs of treatment if their trees are healthy.
Treatment is much less expensive if the tree is in relatively good condition and can allow the owner to save and plan for future removal. Trees may become more expensive to remove as they decline.
When choosing to remove an ash tree, it is best to hire a licensed and insured ISA Certified Arborist or tree service company. Also, homeowners should contact their local municipality to see if they have a list of licensed arborists in their area. Many municipalities have programs to support tree removals and replacements, as well as planting guidelines, so homeowners should check with their local municipality first before hiring an arborist.
Ash tree replacement
Ash trees have been widely planted in Colorado due to their fast growth, ability to tolerate urban conditions and beautiful fall color. However, all untreated ash trees are susceptible to EAB, so homeowners should avoid planting any true ash species (Fraxinus spp.). Instead, consider the following recommendations:
- Focus on tree and landscape-plant diversity. No one tree species should comprise more than 10% of the planted trees growing in any urban or community setting.
- “Plant ahead” and get new trees in the ground that can someday replace ash trees lost to EAB and the shade and other benefits they provided.
An ash tree replacement tool, which includes a list of trees suitable for ash replacement, is available on the Colorado Tree Coalition website.
Insecticide treatment
Ash trees do not have natural defenses for EAB, so trees not regularly treated with insecticide will likely die once infested. Treatment is recommended only if EAB infestations have been verified in a community. If treatment is advised, homeowners can protect high-value trees with treatment by a licensed pesticide applicator every 2-4 years, based on label instructions and current population levels of EAB. Insecticides will be more effective on healthy trees, trees exhibiting no more than 20-40% canopy decline and trees receiving good tree care, such as proper watering and pruning.
Homeowners should educate themselves and use caution when purchasing products that claim to protect trees against a pest such as EAB. Some of these chemicals can be harmful to beneficial insects. They should contact their local municipality or CSU Extension office if unsure about a product.
Homeowners should consult a certified arborist, tree service company or certified pesticide applicator when considering the use of chemical treatments to protect high-value ash trees. They should only hire licensed professionals certified by the Colorado Department of Agriculture to administer treatments.
More information about insecticides used to control emerald ash borer on residential shade trees is available through CSU Extension.
Ash wood utilization
Removed ash trees can be used for firewood, lumber or mulch at the removal site. However, this wood should not be transported to other locations due to the high risk of spreading EAB to healthy trees.
When you need to transport or dispose of EAB-infested wood, the best method is to remove the tree outside the typical adult flight window and debark the trunk and large limbs or chip the wood into pieces smaller than 1 inch by 1 inch prior to moving it. Removals should be made between Sept. 1 and late April to prevent adults from emerging from the wood during transport.
Trees that must be removed during the summer should be taken to a landfill for quick disposal.
Don’t Move Firewood!
Never transport firewood or other untreated wood from ash trees, including logs or nursery stock, as this is the most likely method of accidental spread. Transporting firewood is a primary cause of many costly insect introductions, often due to the larvae’s ability to survive under the bark. When wood is moved from one place to another, pests can hitchhike to new locations and spread further.
Tips for hiring a tree care professional
- Contact your local municipality to learn if there are ordinances restricting who can provide tree services in your community.
- Make sure the professional is an ISA Certified Arborist; you can verify a certification at isa-arbor.com.
- Ask for a written scope of work.
- Verify the professional is insured with both liability insurance and workers compensation.
- Confirm the professional is a licensed pesticide applicator through the Colorado Department of Agriculture (for insecticide treatment only).
- Contact multiple companies to get at least three quotes.
- Look for customer references.
- Don’t fall for high-pressure sales tactics.
- Specify who will remove wood waste and how it will be removed in writing (e.g., mulching).
- Discuss and specify stump removal preferences.