Overview of Diplodia tip blight and canker
Diplodia tip blight is caused by the fungus Sphaeropsis sapinea.
Signs and symptoms of Diplodia tip blight and canker
The most conspicuous symptom of Diplodia blight is brown, stunted new shoots with short, brown needles. Needles on infected new shoots often become discolored while still encased in fascicle sheaths. Entire new shoots may be killed rapidly by the fungus. New shoots throughout the crown may be infected, although damage is generally first evident in the lower crown. In addition to tip blight, the fungus may cause resinous cankers on main stems and branches (seen often in fir trees), misshapen tops, death of cones, blight of seedlings, basal cankers, and sometimes death of entire trees.
Type of Sample Needed for Diagnosis and Confirmation
The Iowa State University Plant & Insect Diagnostic Clinic can help you to investigate and confirm if you plant has this disease. Please see our website for current forms, fees, and instructions on collecting and packing samples. Contact information for each states diagnostic laboratory for U.S. residents. If your sample is from outside of Iowa please do not submit it to the Plant & Insect Diagnostic Clinic without contacting us
Management of Diplodia tip blight and canker
Infection of new shoots can be reduced significantly by fungicides applied at bud swell, one week later, then 2-3 weeks later. Trees may be pruned to improve their appearance, but this practice does not decrease the likelihood of new infections because a great number of fungal spores are released from diseased cones. (Pruning or shearing should be avoided in the spring.) Young pines in plantings may become infected if they are located near old, cone-bearing trees. Either the old infected pines should be removed, or pine seedling beds or plantings should not be located near them.
See this article for more information about canker diseases.