Western Red Cedar brown top

Asked August 10, 2019, 6:55 PM EDT

Hi, I hope you can help. My Western Red Cedar has developed a brown top, and I'm trying to diagnose it and find a treatment plan.

The bark appears clear. no mushrooms. There are some white lacy fibers in the soil, but not a lot.

Any ideas? Appreciate any help.

Clackamas County Oregon

3 Responses

This appears to be an ornamental variety of Thuja, an Arborvitae perhaps? Since the dieback has a distinct transition from healthy to brown, I would look at the stem in the zone of transition to see if there are signs of stem canker lesions. If it is a stem canker fungus, in some cases, after removing the diseased portion, the tree can grow a new top.

The white fibers in the soil could just be decomposer fungi in the leaf litter.

Thanks so much for your response, Glenn. Your suggestions prompted more searches. Do you think it could be this?


Your top dieback doesn't really match what is described for Pestalotiopsis. In order to diagnose a specific pathogen in your case, you will need to look closely at all affected parts, leaves, twigs, and main stem. Look for the point on the main stem where living tissue starts - the live-dead transition is often where we find evidence of the pathogen. Since the top is dead, cutting the top in the live portion, just below the transition from dead to live is a good approach. You could bring this sample to the OSU Extension office and work with the Master Gardeners on the case. It would also be best if you could identify the specific variety (cultivar) of cedar that you have. Also, it is possible that a soil/root problem or root disease is causing this. Cedars and Arborvitae often suffer from soils being either too wet or too dry.