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Diplodia Tip Blight and Canker
Need to know:
- Symptoms of Diplodia blight include brown, stunted new shoots with short, brown needles.
- New shoots may be killed rapidly by fungus, symptoms are adveance throughout the crown.
- Fungicides can be applied at bud swell to reduce infection in new shoots.
- Young pines in planting may become infected if they are located new old, cone-bearing trees.
Overview of Diplodia tip blight and canker
Diplodia tip blight is caused by the fungus Sphaeropsis sapinea.
Symptoms of Diplodia tip blight and canker
Early indications of tip blight are the formation of resin droplets along with the needles at the end of a branch being dead. 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. As the disease progresses, new shoots have short light brown needles that are often wilting. The needles may fade to gray and remain attached to the stem becoming stunted or crooked. 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.
Signs of Diplodia tip blight and canker
Small black structures (pycnidia) can be seen under slight magnification growing in infected needles and even on the scales of mature seed cones. Pycnidia can be placed in a plastic bag with a damp paper towel to allow pycnidia to develop conidia. This process can take two or three weeks and may aid in identification.
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. 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
In order to confirm diplodia tip blight a sample needs to be examined under a microscope. Samples should include dead/dieing tips and pine cones if available. Samples can be places in paper or plastic bags then into a box for shipping. DO NOT add water to samples.
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.
Fungicide applications may be avoided by following good Integrated Pest Management practices like those listed in this encyclopedia article. Often, the only preventative application is effective to manage plant diseases. If the problem requires a fungicide, state law requires the user to read and follow all labels accordingly. For more information, read Proper fungicide use.
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