Swiss Needle Cast Plant Pathology Swiss Needle Cast Swiss needle cast, caused by the fungus Phaeocryptopus gaeumannii, is a disease that we see on Douglas fir in Iowa. The symptoms are very similar to Rhizosphaera needle cast on blue spruce.
Infected needles turn a yellow-brown color and fall from the tree.
The undersides of the infected needles will show rows of small black fungal fruiting structures along the length of the needle. Symptoms typically begin on the lower branches. Also promote good air circulation by adequate tree spacing and weed control, improve tree vigor through mulching and watering when needed, inspect trees for disease before planting, and do not plant susceptible species next to infected trees. Prepared by Paula Flynn , Department of Plant Pathology Iowa State University , Ames, Iowa. This information subject to a usage policy .