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Conifer Disease Quick Reference

 

 

Conifer - Root and Crown Rot

Root and Crown Rots
Hosts: 
All conifers
Pathogens: Assorted root rot fungi/water molds
Signs/Symptoms: Poor growth, branch dieback, discolored and deteriorated roots
More about root and crown rots


Conifer Rhizosphaera Needle

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
More about Rhizosphaera Needle Cast


Conifer - Cytospora Canker

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
More about Cytospora Canker


Conifer - Spruce Needle Drop

Spruce Needle Drop
Hosts: 
Spruces
Pathogen: Unknown (possibly Setomelannoma holmii)
Signs/Symptoms: Needle loss and dieback at or near branch tips


Conifer - Cedar Apple Rust

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)
More about Gymnosporangium Rusts


Phomopsis Tip Blight

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
More about Phomopsis Tip Blight


Conifer - Diplodia Tip Blight

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
More about Diplodia Shoot Blight and Canker


Conifer - Dothistroma Needle_
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
More about Dothistroma Needle Blight

Conifer - Drought Stress

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

Conifer - Winter Injury
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
More about winter injury/winter burn

Conifer - Herbicide Damage
Herbicide Damage
Hosts: 
All conifers
Cause: Exposure to herbicides
Signs/Symptoms: Twisted or otherwise distorted growth, needle yellowing or browning, plant death
More about herbicide damage

Authors:   Brian Hudelson, UW-Madison Plant Pathology
Last Revised:   02/29/2024
D-number:   D0033

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.

 

Send a Plant Sample for Analysis

Be cautious when self-diagnosing plant health issues. Very few diseases can accurately be diagnosed by eye.

Contact the UW Plant Disease Diagnostics Clinic (PDDC), and for a small fee, clinic staff can examine a plant, determine the cause of the disease/disorder, and provide advice on how to control or prevent the issue.

 


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