Search articles from 1992 to the present.
Rhizosphaera Needlecast of Spruce
This article was published originally on 4/21/2000
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 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. A close look at discolored needles shows orderly lines of black spots (a hand lens may be helpful). These are fruiting bodies of the fungus that have developed in the stomata (natural openings) of the spruce needles. Unless control measures are taken this disease will spread and worsen year after year and may eventually kill the entire tree.
Year of Publication:
IC-483(8) -- April 21, 2000