Emerald Ash Borer Signs and Symptoms

Identifying the emerald ash borer can be challenging because both adults and larvae are hard to find. The best way to detect an infestation is by monitoring the health of ash trees and looking for signs and symptoms of the emerald ash borer. A sign is physical evidence of a pest, while a symptom is a change in the tree that indicates a problem. 

How is the City Handling Emerald Ash Borer? 

Importance of Oregon Ash Trees

Oregon ash is a vital native tree that grows along rivers, streams, and wetlands in the Willamette Valley. Salem has over 90 miles of streams within its limits, which means there are many ash trees in the area. Unfortunately, these trees will be significantly affected by the emerald ash borer, a pest that threatens their survival. 

Emerald ash borer will kill most ash trees in Oregon. Since there is no way to stop this pest, the City is taking steps to plan, prepare, respond, and recover from its impact. The EAB Response Plan will outline how the City will address key questions about emerald ash borer in Salem, including: 

• Where are our ash trees?
• How do we prioritize trees for treatment or removal? 
• What actions can we take and where?
• How do we inform the public about emerald ash borer and help the community respond? 

EAB Response Plan

The City is currently working on the EAB, or emerald ash borer, Response Plan. Once it is finalized, it will be shared with the public. The plan will cover important topics, including: 

Inventory

One of the first steps in managing emerald ash borer is understanding the extent of the problem in Salem. This begins with an inventory of ash trees on City-owned properties. Salem staff are using online mapping tools to survey public areas, parks, and natural spaces. They will identify ash trees, assess their health, and determine the risks they pose when they die. 

In areas with a small number of ash trees, such as parks or along streets, staff will evaluate each tree's health and gather data. In larger parks like Minto-Brown Island Park, staff will focus on ash trees that could threaten important assets, such as homes, trails, roads, and power lines. 

Parks and Urban Forestry have been mapping street and park trees for several years and are close to completing their inventory. The goal for 2025 is to finish the inventory for public areas, so we have a clear understanding of the number and location of ash trees that will be affected. 

Prioritization

Ash trees are very common in Salem because they can grow almost anywhere and provide shade and habitat. However, there are more ash trees than we can manage at once. Due to limited staff time and funding, we must prioritize how we handle ash trees. 

To help decide which trees to manage first, we will consider the following categories: 

• Proximity to known emerald ash borer outbreaks
• Tree health
• Risk to people and property if the tree dies
• Canopy cover in the area
• Recommended treatment (removal, insecticide treatment, or planting other species)
• Underserved communities
• Wildfire risk

Actions

Even though emerald ash borer is here to stay, slowing its spread can still make a big difference. Slowing the spread will give everyone in Oregon more time to prepare and respond, ultimately saving money. When deciding what to do with ash trees, we have several options. 

Take No Action: This option means accepting that the ash tree will likely become infected and die. It is best for large natural areas where a fallen tree will not impact homes, buildings, trails, or roads. This option is also reasonable in areas where other trees and shrubs can provide similar benefits. 

Underplant: Ash trees provide valuable habitat and shade, especially near rivers and streams. When emerald ash borer infects these trees, it can create large gaps in the canopy, leading to higher stream temperatures and invasive species taking over. 

Underplanting existing ash trees with native trees and shrubs can help these species establish themselves before the ash trees die. 

Remove: Since most ash trees will die, removing them before they become a hazard can be the safest and most cost-effective choice. Smaller trees, those under 6 inches in diameter, are usually quick and easy to remove. The benefits lost from the tree can be regained by a newly planted tree within a few years. 

Trees that pose a significant risk to health and safety when they die should also be considered for removal. Be sure to check the City's website Tree Removal on Your Property to see if you need a permit to remove your tree. 

Treatment: Insecticide treatments can effectively protect ash trees from emerald ash borer and help them live out their natural lives. Emerald ash borer larvae damage trees by feeding under the bark, where water and nutrients flow. Emerald ash borer-approved insecticides are absorbed by the tree and spread throughout the inner bark. When emerald ash borer larvae feed on a treated tree, they die. 

The City of Salem is using a systemic pesticide injected directly into the tree just above the roots. This method minimizes the risk to non-target insects, such as bees and butterflies. 

City staff are learning how to complete this treatment and secure pesticide applicator licenses. Treatments will need to occur every 2-3 years for the tree's life but can be more cost-effective than removing a large ash tree. 

Trees prioritized for treatment include those over 6 inches in diameter, along public rights of way, that are in good health. Other ash trees may also be included in treatments if appropriate. 

What Can You Do?

All ash species in Oregon are at risk of emerald ash borer. Once infested, a tree will die within 3-7 years. As ash trees die, they become brittle and can pose hazards to people, property, and infrastructure. The most important step you can take is to check if your property has any ash trees. 

While the City manages ash trees on public property, private property owners are responsible for their trees. Here are some options for managing ash trees: 

Prevention

The best way to reduce the impact of emerald ash borer is to slow its spread. Here are some actions you can take. 

• Do not move firewood. 
• Buy or collect firewood within 10 miles of where you plan to burn it. 
• Follow the Oregon Department of Agriculture's emerald ash borer quarantine, which includes Washington, Yamhill, Marion, Clackamas, and Multnomah counties. Emerald ash borer primarily spreads when people move infested wood to new locations. Help combat the spread by not moving ash tree, olive tree, or white fringetree material outside the quarantine area. 

Protection

While all ash trees in Oregon are susceptible to emerald ash borer, stressed trees that receive too little water, sunlight, or are already diseased will attract the pest first. You can help protect your ash trees and the environment by: 

• Caring for ash trees by watering and pruning them as needed, but avoid doing so during high emerald ash borer activity (April through October). 
• Learning to identify signs and symptoms of emerald ash borer. 
• Reporting signs or symptoms of emerald ash borer to the Oregon Invasive Species Hotline online or by calling 1-866-INVADER.
• Noting the number of ash trees you have and making a management plan for how you will respond to emerald ash borer. 
• Protecting trees when it makes sense. Large, well-established ash trees may be good candidates for protection using injected insecticide. When properly applied by a trained and licensed pesticide applicator, insecticide treatments can be up to 95 percent effective. This is a long-term commitment; selected ash trees will need treatment every 1-3 years. 
  • Read the EAB Treatment Fact Sheet created by the Oregon Department of Forestry to learn more about insecticide options

Streamside landowners in Salem can request a free site visit to help with ash tree identification by emailing stormwateroutreach@cityofsalem.net.

Removal

It is not recommended to cut down healthy ash trees, olive trees, or white fringetrees before emerald ash borer is confirmed in the area. Large, healthy trees can continue to provide benefits for many years before emerald ash borer affects them. Before deciding to remove a tree, check the City’s Tree Removal Permit webpage to see if you need a permit. 

When deciding if removal is the best option for your ash tree, consider: 

• Tree Size: Trees under 6 inches in diameter are good candidates for removal because they are relatively cheap to replace. The benefits lost can be restored in a few years with a replacement tree. 
• Tree Health: Removal is often best for trees in poor health. Signs include canopy decline and dead leaves or branches. Trees with over 30 percent canopy decline are unlikely to survive long. 
• Tree Location: Ash trees near buildings or infrastructure can become hazards as they die. An ISA-certified arborist can help with this decision. Treesaregood.org is a helpful resource for finding qualified professionals. 
• Tree Value: If a tree provides shade or has aesthetic or sentimental value, insecticide treatment may be better than removal. Over 20 years, treatment can cost less than removal or replacement. If the tree is not valuable, the benefits of removal may outweigh the losses. 
• Timing: Since ash trees become brittle as they die, it is best to remove them before they show significant decline. Many arborists will not climb trees with 20-30 percent canopy decline, requiring specialized equipment for safe removal. This can make removing a dead or dying tree two to three times more expensive than removing a healthy one. 

Before cutting down ash trees, plan how to responsibly handle the wood waste. In Marion County, you cannot move the wood outside the county unless it goes to Washington, Yamhill, Clackamas, or Multnomah counties due to the emerald ash borer quarantine. 

It is best to leave infested tree material onsite as wood chips, firewood, or decaying material. If it cannot be left, move it as little as possible to reduce the risk of spreading emerald ash borer. 

For areas with many urban ash trees needing treatment or removal, consider partnering with neighbors to pool resources and accept bids from arborists. Arborists may offer better prices for working on multiple trees in one area. 

Replacement

When selecting replacement trees, consider factors such as soil conditions, distance to buildings and other trees, impermeable surfaces, root expansion, habitat value, climate adaptability, and the final height and shape of the tree as it matures. 

A great way to start is by looking at the size, location, and habitat of your current ash tree and choosing a replacement that meets similar criteria. 

Check out some of these resources to pick the right tree for you:

• Alternatives to Ash in Western Oregon
• Native Plants for Willamette Valley Yards
• Choosing Native Plants for Your Garden

The City of Salem and other local partners also offer programs that provide replacement trees for free or at reduced costs for qualifying properties: 

• Free Trees for Streams Program
• Watershed Protection and Preservation Grant
• Marion County Soil and Water Conservation District Grants
• Oregon Watershed Enhancement Board (OWEB) Small Grants