Blue Spruce Getting Sparse
I have nine blue spruce surrounding my swimming pool. They are 35 - 40 feet tall. Even though there's new growth, I'm noticing some sparse, dead-looking sections. Not sure if it's just natural die-back that occurs as the trees get taller. Or, if there's something bad happening. There are some brown spots. There also seems to be some mossy type growth on some of the branches. Not sure any of it means anything. Attached a few photos to see what the experts think.
Oakland County Michigan blue spruce
I can't tell exactly what may be going on from your photos. It could be normal needle loss but i suspect the trees may have a needlecast disease.
There are three principle types of diseases that affect blue spruce trees: needlecasts, tip blights and canker diseases.
As the name implies, trees with needlecast diseases shed needles. Needlecast fungi often infect needles on the current year’s shoots. As the disease progresses, the needles die, usually the year following the infection. As a result, trees affected by needlecasts often have an outer “shell” of live needles on current shoots and dead needles on older shoots. The two most common needlecasts we find in spruce are caused by the fungal pathogens Rhizosphaera and Stigmina/Mycosphaerella.
Fungicides that are available to control needlecast are preventative. Well-timed sprays can prevent new infections. Time your first application in the spring after the new growth has expanded to 0.5 to 1.5 inches in length. New growth typically appears in May. Follow-up with 1-2 additional sprays as indicated on the fungicide label. Fungicide applications will need to be applied for at least 2-3 consecutive years and maybe more. Fungicides that are labelled for control contain the active ingredients of either chlorothalonil, mancozeb or copper. Remember to read and follow the instructions on product labeling. You can send a sample to MSU Diagnostic Services to determine what is going on. www.pestid.msu.edu There is a fee.
For more information –
What is spruce decline? http://msue.anr.msu.edu/news/what_is_spruce_decline_and_what_should_you_do_about_it
The gray-blue patches on the twigs are lichens. These are interesting organisms, however, do not cause disease problems. They live and gather sunlight on twigs or branches but do not infect the tree. Many lichens grow rapidly when exposed to full sunlight, which explains why we find them on stressed trees.