What Is Causing Pale Green Color At Top Of Some Mature Arborvitae

Question From: R. Brantley - Ridgefield, Washington, United States
Q: Hi Nancy- we have several mature (20 + year old) arborvitae that are healthy looking but the top 1/4 of them is turning a pale green. No bugs apparent- had spider mites on the 50 or so trees earlier in spring but treated and rid them. Had some thrips, too, but also went away with the treatment. Going to spray with neem this fall, but what could the discoloration be on only about 4 of the 50 trees? 2 are next to each other. We live in south west Washington State (Vancouver, WA). Thank You!

A: My guess would be insects. You may have missed areas on these trees. I would get an on-site inspection by a certified arborist for a more accurate ID and method of control - you can find an arborist at tcia.org. Best And Happy Yardening, Nancy