Sitka Spruce aphids

Asked October 18, 2019, 11:13 AM EDT

I have two spruce trees that lost all of their needles this last year. They both have recovered. I learned that the culprit probably was aphids. Does this sound correct? Do you know the life cycle of these insects? I have found interesting 1/2 mm bugs on the side of my house near the trees. They look like a grub but have a camouflage shell and seem to put out a small web or fiber.

Lincoln County Oregon

1 Response

Hello and thank you for your questions. Yes, Sitka spruce are being defoliated up and down the entire Oregon coast and in parts of northern California. It's good to hear that your trees have recovered!

The spruce aphid feeds during the winter months when trees are dormant as they favor a specific nitrogen content, which is also why only older needles are defoliated. Once trees "awaken" from dormancy, aphid populations crash, with the help also from natural enemies (mostly other insects). If trees can keep newer needles, they are expected to recover within 3-5 years, or so.

I have attached the Forest Health Fact Sheet for spruce aphid for your information.
https://www.oregon.gov/ODF/Documents/ForestBenefits/Spruce_aphid_2017.pdf

Should you have any further questions, please do not hesitate to contact me, as I am the Extension Forester for Lincoln County.

Thank you!