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Conifer Disease Quick Reference

Brian Hudelson, UW-Madison Plant Pathology
Revised:  1/12/2019
Item number:  XHT1025

Root and Crown Rots
Hosts
: All conifers
Pathogens: Pythium spp., Phytophthora spp., Rhizoctonia solani, Fusarium spp., Cylindrocarpon spp.
For more information see: UW Garden Facts XHT1070

Root and crown rots
Root and crown rots

Rhizosphaera Needle Cast
Hosts: Colorado blue spruce, other spruces, many other conifers
Pathogen: Rhizosphaera kalkhoffii
For more information see: UW Garden Facts XHT1006 and UW-Extension Bulletin A2640

Close up photo of diseased tree needle.
Rhizosphaera Needle Cast

Cytospora Canker
Host
: Colorado blue spruce, other spruces
Pathogen: Cytospora kunzei
For more information see: UW Garden Facts XHT1003 and UW-Extension Bulletin A2639

Cytospora Canker

Spruce Needle Drop
Hosts
: Spruces
Pathogen: Unknown (thought possibly to be Setomelannoma holmii)

Spruce Needle Drop

Gymnosporangium Rusts
Hosts: Junipers, apple, crabapple, hawthorn, quince
Pathogen: Gymnosporangium spp.
For more information see: UW Garden Facts XHT1009 and UW-Extension Bulletin A2598

Gymnosporangium Rusts

Phomopsis Tip Blight
Host
: Junipers
Pathogen: Phomopsis juniperovora
For more information see: UW Garden Facts XHT1099

Phomopsis Tip Blight

Diplodia Tip Blight
Hosts
: Pines (Austrian, red, jack, Scots, mugo), many other conifers
Pathogen: Diplodia spp.
For more information see: UW Garden Facts XHT1010 and UW-Extension Bulletin A3643

Diplodia Tip Blight

Dothistroma Needle Blight
Hosts: Pines (Austrian, red, Scots, mugo, ponderosa, and others)
Pathogen: Dothistroma pini
For more information see: UW Garden Facts XHT1078 and UW-Extension Bulletin A2620

Dothistroma Needle Blight

Drought Stress
Hosts
: All conifers
Cause: Insufficient water

Drought Stress

Winter Injury
Hosts
: All conifers, particularly yews and junipers
Cause: Dehydration over the winter

Winter Injury

Herbicide Damage
Hosts: All conifers
Cause: Exposure to a growth regulator herbicide such as 2,4-D or dicamba
For more information see: UW Garden Facts XHT1004 and UW-Extension Bulletin A3286

Herbicide Damage

 

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

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