Cytospora Canker on Spruce
Gary W. Moorman, Professor of Plant Pathology
Blue and Norway spruces are susceptible to a branch killing disease caused by the fungus Cytospora kunzei. Cankers, sunken dead areas of bark and underlying wood, form on the lower branches of the trees girdling small branches in one or two years and large branches after several years. Resin flows out of the cankers and may drip down on lower branches.
Cytospora can infect branches through wounds and branch stubs but does not actively develop a canker unless the tree is stressed by drought. Small fungal structures, in which thousands of spores form, develop in the canker. However, during wet weather, the spores ooze out in long yellowish threads. Rain splashes the spores to other branches and branch killing proceeds up the tree.
Since the fungus readily infects wounded tissue but remains latent in the tree without causing symptoms, fungicide sprays cannot be effectively timed to prevent this disease.
Select the planting site carefully, avoiding drought prone sites. Anticipate the future needs of the mature tree and consider whether the site has the potential of supplying the water requirements of a 50-60' tall specimen.
Prune infected branches, disinfesting the tools between cuts.
Blanchard, R. O. and T. A. Tattar. 1981. Field and laboratory guide to tree pathology. Academic Press. New York. 285 pp.
Schoeneweiss, D. F. 1983. Drought predisposition to Cytospora canker in blue spruce. Plant Disease 67:383-385.
Resin oozing from canker on branch
Dying lower branches
Notice: The user of this information assumes all risks for personal injury or property damage.
Warning! Pesticides are poisonous. Read and follow all directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams or ponds.
Issued in furtherance of Cooperative Extension work, Acts of Congress, May 8 and June 30, 1914, in cooperation with the U. S. Department of Penn State College of Agricultural Sciences research and extension programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
Visit Penn State Extension on the web at extension.psu.edu.
Where trade names appear, no discrimination is intended, and no endorsement by Penn State Cooperative Extension is implied.
This publication is available in alternative media on request.
The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V, 814-863-1150/TTY.