Tree Care and Maintenance

Seasonal Tree Care Tips: Summer 2022
Emerald Ash Borer


Photo Credit: Close-up of an adult female emerald ash borer feeding on an ash leaf; length ranges from 0.33 to 0.53 inches, that’s smaller than a penny. Credit: Leah Bauer, USDA Forest Service Northern Research Station,

Emerald ash borer (EAB), an invasive beetle that infests ash trees, was discovered in Forest Grove, Oregon, on June 30, 2022. This is the first time EAB has been identified in Oregon, but the state has been preparing for its arrival for years.

EAB was first discovered in the United States in Michigan in 2002, likely arriving in wood packing materials from Asia. This metallic wood-boring beetle threatens all species of ash tree (Fraxinus genus) and is considered the most destructive forest pest ever seen in North America with the potential to create billions of dollars in damages nationwide. EAB has killed hundreds of millions of ash trees across the east coast and Midwest over the last 20 years. Here in Oregon, loss of our native ash tree, Oregon ash (Fraxinus latifolia), a very important riparian and wetland species west of the Cascades, is of grave concern, as well as the loss of widely planted non-native and cultivated ash trees in urban landscapes.

Unfortunately, there are no effective means of eradicating EAB, but here’s what you can do to help:

  1. Be on the lookout for EAB. Learn to identify ash trees and EAB (there are many look-alikes), and report suspected sightings immediately.
  2. Don’t actively plant ash trees, but take good care of the ash trees you have. This includes providing supplemental water during summer heatwaves, treating high-value ash trees with systemic insecticides, and removing dead and dying ash trees and replanting with another species suitable for the specific site conditions. A qualified and experienced plant health care specialist can prescribe and implement appropriate treatments.
  3. Don’t move firewood and be sure to dispose of ash wood properly.
  4. Learn more about EAB by visiting these resources:


 Please check back for more seasonal tree care and maintenance advice!

Link to Tree Care and Maintenance Archives


Fall 2021: Healthy Trees are Defended Trees

Special Edition: After the Storm

Winter 2021: What is an Arborist?

Fall 2020: Soil Management  

Summer 2020: Retaining and Creating Snags for Wildlife

Spring 2020: Mulch: Numerous Benefits and Easy Application

Winter 2020: Tree Planting: To Stake or Not to Stake?

Fall 2019: Insects and Diseases

​Summer 2019: Drought Stress Revisited

Spring 2019: Trees and Construction

Winter 2019: Topped Tree

Fall 2018: Autumn Leaves

Summer 2018: Emerald Ash Borer

Spring 2018: Pruning Young Trees

Winter 2017: Tree Related Storm Damage

Fall 2017: New Tree Selection and Planting

Summer 2017: Trees and Turfgrasses

Spring 2017: English Ivy Removal

Winter 2017: Recognizing Tree Risk

Summer 2016: Drought Stress

Fall 2016: Preparing Trees for Winter


Additional Tree Care Resources:

National Arbor Day Foundation The Morton Arboretum
Oregon Department of Forestry Tree Care Info
ISA Find an Arborist Alliance for Community Trees
Oregon Department of Forestry  


Right Tree in the Right Place

Use this handy guide for assistance in choosing the right species of tree based on the constraints of a site, such as overhead wires, narrow plant strips, and proximity to structures.

"Right Tree Right Place" - helpful information such as "Use this guide for assistance in choosing the right species of tree based on the constraints of a site, such as overhead wires, narrow plant strips, and proximity to structures."

"Master Plant List" - a guide to the plants that are acceptable for mitigation requirements in Lake Oswego.