Because stomata are linearly arranged, the black dots, or fruiting structures of the fungus, characteristically line up in neat rows on the needles. Affected branches are eventually defoliated and killed by the fungus. Disease development is favored by poor air circulation and high relative humidities. Control of unwanted weeds and shrubs in the vicinity of trees is important in increasing air movement and decreasing environmental conditions necessary for infection. Fungicide applications may be required to suppress further infection on diseased trees.
Proper timing is critical for disease control.
Applications should be made just as new shoot growth is to 1 inch long. A second application after 3 weeks is recommended. Rhizosphaera Needlecast of Spruce . K-State Research and Extension, Plant Pathology.