Q. One of our cedar trees has brown tips on the needles in one area of the tree. Both pictures are of different sides of the same tree. The brown area developed almost overnight about three weeks ago. We have not done any digging or grading in the yard from 15 years. I hope you might give us some idea of what might be causing this. Wayne Asplund – Bonney Lake, WA
A. From the picture you sent me I think what you are seeing is a fungal disease called leaf blight or tip blight. Our Western Red Cedar is a Thuja related to the Common Arborvitae so this disease can be seen on these plants as well. The fungus that is most likely to attack the Western Red Cedar is Cedar Leaf Blight or sometimes Kethia Blight (Didymascella thujina) one of the few diseases to be successful against these normally insect and disease resistant trees. The fungus overwinters on the needles of the trees or in the cast-off needles previously diseased needles. The spores start germinating in the spring during which time the fungus commandeers the needles resources (causing them to yellow) to produce more spores usually from late summer to early fall. You may be wondering why after all these years the disease has appeared. Most likely the trees became fuller as they got older and now there is less air circulation through the tree. Moisture is necessary for the fungal life cycle. Fungicides with fixed copperin them like COPPER DUST & SPRAY are appropriate for control. Since you have a large tree I would suggest you have a certified arborist take a look at the tree to verify that this is a fungus and to spray/treat the tree. The arborist may also suggest some judicious pruning to allow for better air circulation. Sometimes this disease is confused with normal fall leaf shedding, but since you have only seen these symptoms in the last week I suspect Cedar Leaf Blight.