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
Rhizosphaera Needle Cast
Hosts: Colorado blue spruce, other spruces
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
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 D0037
Spruce Needle Drop
Hosts: Spruces
Pathogen: Unknown (possibly Setomelannoma holmii)
Signs/Symptoms: Needle loss and dieback at or near branch tips
Gymnosporangium Rusts
Hosts: Juniper, 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
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
Diplodia Shoot Blight and Canker
Hosts: Austrian pine, 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
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
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
Winter Injury/Winter Burn
Hosts: All conifers, particularly yew and juniper
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
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
For more information on conifer diseases:
See the UW-Madison Plant Disease Diagnostics Clinic website (https://pddc.wisc.edu/) or contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at 608-262-2863 or pddc@wisc.edu.
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An EEO/Affirmative Action employer, University of Wisconsin-Madison Division of Extension provides equal opportunities in employment and programming, including Title IX and ADA requirements. This document can be provided in an alternative format by calling Brian Hudelson at 608-262-2863 (711 for Wisconsin Relay).
Thanks to Ann Joy, Patti Nagai and Ann Wied for reviewing this document and to Bria Radtke for supplying the photo of spruce needle drop.
A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website. (https://pddc.wisc.edu)
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