The dead lower branches in these Austrian pines (Fig. 1) are due to Diplodia (= Sphaeropsis) tip blight. The causal fungus infects newly elongating shoots, in late spring, resulting in stunting and death of the new growth (Fig. 2). Black spore-bearing structures of the causal fungus are formed at the base of the stunted brown needles and on infected cones (Figs 3 and 4). Austrian pines are very susceptible to the disease, and infected trees often lose ornamental value as twigs are killed year after year. For more information on this disease, refer to BP-24-W, which can be found at: https://www.purduelandscapereport.org/resource/diplodia-tip-blight-of-two-needle-pines/
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- Figure 1. Mature Austrian pine trees with dead lower branches due to Diplodia tip blight.
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- Figure 2. An elongating shoot which was killed by Diplodia tip blight (Note stunted, dead needles).
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- Figure 3. Spore bearing structures (black dots) of Diplodia on pine cone scales.
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- Figure 4. Black spore bearing structures of Diplodia on an infected pine needle.
