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The dead lower branches in these Austrian pines (Fig. 1) are due to Sphaeropsis tip blight (formerly called Diplodia 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, similar in size to a period on this page, are formed at the base of the stunted brown needles. 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: http://www.ces.purdue.edu/extmedia/BP/BP_24_W.pdf
--Karen Rane, Plant Disease Diagnostician, Purdue University
Figure 1 courtesy of Karen Rane, Plant Disease Diagnostician, Purdue University
Figure 2 courtesy of Gail Ruhl, Interim P&PDL Director
Plant and Pest Digital Library and Digitally Assisted Diagnosis, Purdue University, West Lafayette, Indiana.