Spruce tree needles browning

Asked July 22, 2015, 10:01 PM EDT

We have 6 Black Hills Spruce trees that the needles have dramatically started to brown within the last couple months. The trees are all around 20 feet tall and have always been healthy. These are at our cabin in Lake County near Gooseberry Falls. We hadn't been up there for 6 weeks and immediately noticed the problem upon our arrival. The tips look fine but more inner needles are browning. The trees have lots of small brownish/gray moths all over them too which may just be a coincidence but we have never seen them like this in the 12 years we have had our property. We noticed several other trees in Gooseberry Park and along highway 61 that appear to have the same problem. We spoke with a naturalist at Gooseberry and he thought it was from the lack of snow this last winter and could be frost damage. He said if it continues it may be a fungus. Our trees looked fine all spring so it didn't appear as frost damage. I have attached a couple photos I took. I was hoping someone may have an idea of what the problem might be and a treatment plan to save our beautiful trees. Thank you for looking at this. Any suggestions you might have would be wonderful.

Lake County Minnesota black hill spruce spruce diseases

1 Response

Thank you for the question. There are several needle fungi that can cause brown needles. It is often one of two different types—Cytospora Canker and Rhizosphaera Needle Cast. Trees with Rhizosphaera needle cast are usually affected first on the inside of the tree, working out, and at the bottom of the tree, working up. This disease is most apparent on older needles on the tree. If you see scattered branches with areas on the bark leaking abundant white, sticky resin on dead branches then they have Cytospora canker. It could also be mite damage. Mites are tiny spider-like creatures that suck the sap from spruce needles, so that when viewed under magnification the needles appear speckled with yellow flecks. You can scout for mites by shaking a symptomatic branch over a white sheet of paper and then looking for tiny, moving dots (mites). The following site has more information. http://www.extension.umn.edu/distribution/horticulture/M1265.html

Thank you for contacting Extension.