This week the majority of questions and samples received in the Plant Disease Clinic were of a fungal disease, Rhizosphaera needlecast. Blue spruce trees are particularly susceptible to this disease. While this needle disease is common in Iowa and doesn't usually kill the tree, it can cause significant aesthetic losses in the landscape. Symptoms Symptoms are first observed as a yellowing of mature needles in late summer and fall. The next spring implications become obvious as affected needles turn a purple-brown color and drop from the tree.
Symptoms appear initially on lower branches then gradually affect higher and higher branches.
Affected branches lose the older inner needles first, leaving a tuft of young green needles at the ends. Eventually the entire branch can be killed. Unless control measures are taken this disease will spread and worsen year after year and may eventually kill the entire tree. Management Trees stressed by environmental factors are more susceptible. Choose a suitable site for planting blue spruce.