Conifer Disease Quick Reference
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 05/17/2021
D-number: XHT1025
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Root and Crown Rots Hosts: All conifers Pathogens: Assorted root rot fungi/water molds. Signs/Symptoms: Poor growth, branch dieback, discolored and deteriorated roots For more information see: UW Plant Disease Facts D0094
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Rhizosphaera Needle Cast Hosts: Colorado blue spruce, other spruces, other conifers Pathogen: Rhizosphaera kalkhoffii Signs/Symptoms: Browning/purpling of interior needles of lower branches, followed by needle drop For more information see: UW Plant Disease Facts D0093
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Cytospora Canker Hosts: Colorado blue spruce, other spruces Pathogen: Cytospora kunzei Signs/Symptoms: Branch dieback with milky-white patches of dried sap on affected branches For more information see: UW Plant Disease Facts D0033
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Spruce Needle Drop Hosts: Spruces Pathogen: Unknown (thought possibly to be Setomelannoma holmii) Signs/Symptoms: Needle loss and dieback at or near branch tips
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Gymnosporangium Rusts Hosts: Junipers, apple, crabapple, hawthorn, quince Pathogen: Gymnosporangium spp. Signs/Symptoms: Brown blobs with orange gelatinous masses (juniper); yellow/orange leaf spots (other hosts) For more information see: UW Plant Disease Facts D0058
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Phomopsis Tip Blight Hosts: Junipers Pathogen: Phomopsis juniperovora Signs/Symptoms: Browning and dieback of branch tips in spring and early summer as new growth emerges For more information see: UW Plant Disease Facts D0077
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Diplodia Shoot Blight and Canker Hosts: Austrian pone, other pines Pathogen: Diplodia spp. Signs/Symptoms: Dieback of branch tips with dead needles showing uneven lengths For more information see: UW Plant Disease Facts D0042
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Dothistroma Needle Blight Hosts: Austrian pine, other pines Pathogen: Dothistroma pini Signs/Symptoms: Needle tip browning and death with a distinct break between live and dead tissue For more information see: UW Plant Disease Facts D0043
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Drought Stress Hosts: All conifers Cause: Insufficient water Signs/Symptoms: Purpling/browning of needles near branch tips or higher up in plants during the summer
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Winter Injury Hosts: All conifers, particularly yews and junipers Cause: Insufficient water Signs/Symptoms: Needle browning/bleaching over winter or in spring as plants come out of dormancy For more information see: UW Plant Disease Facts D0127
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Herbicide Damage Hosts: All conifers Cause: Exposure to herbicides Signs/Symptoms: Twisted or otherwise distorted growth, needle yellowing or browning, plant death For more information see: UW Plant Disease Facts D0060
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