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Conifer Disease Quick Reference

Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 04/30/2021
D-number: XHT1025
Conifer - Root and Crown Rot

 

Root and Crown Rots
Hosts: All conifers
Pathogens: Pythium spp., Phytophthora spp., Rhizoctonia solaniFusarium spp., Cylindrocarpon spp.
Signs/Symptoms:  Poor growth, branch dieback, discolored and deteriorated roots
For more information see: UW Garden Facts XHT1070

 

Conifer Rhizosphaera Needle

 

Rhizosphaera Needle Cast
Hosts: Colorado blue spruce, other spruces, many other conifers
Pathogen: Rhizosphaera kalkhoffii
Signs/Symptoms:  Browning/purpling of interior needles of lower branches, followed by needle drop
For more information see: UW Garden Facts XHT1006

 

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
For more information see: UW Garden Facts XHT1003

 

Conifer - Spruce Needle Drop

 

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

 

Conifer - Cedar Apple Rust

 

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 Garden Facts XHT1009

 

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
For more information see: UW Garden Facts XHT1099

 

Conifer - Diplodia Tip Blight

 

Diplodia Shoot Blight and Canker
Hosts: Pines (Austrian, red, jack, Scots, mugo), many other conifers
Pathogen: Diplodia spp.
Signs/Symptoms:  Dieback of branch tips with dead needles showing uneven lengths
For more information see: UW Garden Facts XHT1010

 

Conifer - Dothistroma Needle_

 

Dothistroma Needle Blight
Hosts: Pines (Austrian, red, Scots, mugo, ponderosa, and others)
Pathogen: Dothistroma pini
Signs/Symptoms:  Needle tip browning and death with a distinct break between live and dead tissue
For more information see: UW Garden Facts XHT1078

 

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
Hosts: All conifers, particularly yews and junipers
Cause: Dehydration over the winter
Signs/Symptoms:  Needle browning/bleaching over winter or in spring as plants come out of dormancy
For more information see: UW Garden Facts XHT1239

 

Conifer - Herbicide Damage

 

Herbicide Damage
Hosts: All conifers
Cause: Exposure to a growth regulator herbicide such as 2,4-D or dicamba
Signs/Symptoms:  Twisted or otherwise distorted growth, needle yellowing or browning, plant death
For more information see: UW Garden Facts XHT1004

 

For more information on conifer diseases: Contact your county Extension agent.


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