OregonSaves Deadline Set for March 2023

Emerald ash borer exit holes from infested tree. Credit: C. Buhl (ODF Forest Health)

cannot be saved, do not waste resources trying to spray or chemically treat infested trees. Prompt removal is advised.

Where should cities look for guidance on ash tree treatments?

Chemical treatment specifically to prevent infestation by emerald ash borer is available but should be applied prior to the arrival of the insect in one’s community, as previously described. Such treatments also must be repeated over time as their effectiveness wanes after a couple years. The Oregon Department of Agriculture, which is the lead agency in EAB response, regulates pesticide use in Oregon and will have guidance on what treatments can be safely used in Oregon. Check with your local urban forestry professionals or OSU Extension agent to see what treatment may make sense for your situation and be allowed in your local area (some jurisdictions may have local restrictions on certain classes of pesticides). It’s best to purchase treatments from reputable tree-care companies to avoid ineffective or fraudulent applications.

Should Cities be Actively Looking for EAB?

City staff that work in parks and around street trees should be familiar with the signs and symptoms of EAB, and keep this information “front of mind” when working outside. Cities can also provide links to the Oregon Department of Agriculture’s Emerald ash borer found in Forest Grove earlier this summer.

EAB webpage (tinyurl.com/y9ev7kwr) on their city webpage to help make its residents aware of this pest. However, city staff and city residents should also be reminded that drought, disease, and other factors can make ash trees look unhealthy, so they should not presume their declining ash have EAB yet. Also, there are several native emerald ash borer “look alike” beetles. So, if one sees a green metallic beetle—don’t panic!—but do try to document it with clear photos (or by capture) and report it to the Oregon Invasives Hotline at www.oregoninvasiveshotline.org.

What about planting new trees when the ashes are removed?

To maintain the livability of many Oregon cities, the cities should plan to replace the ashes they lose to EAB. The best defense against future pest infestations and climate change-related tree decline is to create urban forests with as much species diversity as possible—with native and non-native trees, as well as through judicious planting of cultivated tree varieties. When planning for and planting trees, ensure there is ample space for roots with good quality soil, no overhead obstructions such as powerlines, and consistent irrigation for the first five years. Research replacement tree species that are likely to be more drought and pest resistant. Local city urban forestry programs often have lists of trees recommended for your local community. Search for those online.

Does EAB attack any other tree species?

No. EAB only attacks ash trees (Genus Fraxinus). If you have more questions about EAB, please get in touch with us at urbanforestry@odf.oregon.gov. If you want to report a suspected EAB infestation, please use the Oregon Invasives Hotline, linked above. Periodically, we will be hosting webinars and other virtual gatherings with experts to discuss how best to respond to EAB, and where in the state it has been detected. Use urbanforestry@odf.oregon.gov to let us know if you would like to be included in a list to be notified when we are holding these sessions.