Category Archives: Quick Reference Guide

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Problems to Watch for in 2026

January 8, 2026 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 4/14/2026

D-number: D0137

Root and Crown Rots

Hosts: Any plant
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

Planting-Related Issues/Decline

Hosts: Woody trees and shrubs
Pathogens: None (abiotic)
Signs/Symptoms: No visible root flare, girdling roots, frost cracks, canopy thinning, early fall color, branch dieback, tree/shrub decline and death

Scab (Apple and Pear)

Apple Scab

Hosts: Apple, crabapple, pear, mountain-ash
Pathogens: Venturia inaequalis, Venturia pirina
Signs/Symptoms: Feathery-edged spots on leaves and fruits often leading to leaf loss and tree defoliation
For more information see: UW Plant Disease Facts D0004

Septoria Leaf Spot of Lilac

Host: Lilac
Pathogen: Septoria sp.
Signs/Symptoms: Dead spots on leaves, potentially leading to complete leaf browning

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 D0058/0131

Chlorosis

Hosts: Pin oak, red maple, birch, azalea, white pine, blueberry
Pathogen: None (Abiotic)
Signs/Symptoms: Yellow leaves with dark green veins
For more information see: UW Plant Disease Facts D0030

Septoria Leaf Spot and Early Blight

Host: Tomato
Pathogens: Septoria lycopersici and Alternaria solani
Signs/Symptoms: Spotting and eventual total death of leaves working from the bottom of the plant up
For more information see: UW Plant Disease Facts D0100/46

Powdery Mildew

Hosts: Herbaceous and deciduous woody ornamentals, fruits, vegetables, turf
Pathogens: Miscellaneous powdery mildew fungi
Signs/Symptoms: Powdery white growth on leaves
For more information see: UW Plant Disease Facts D0084/86/87

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

Diplodia Shoot Blight and Canker

Hosts: Austrian pine, other pines
Pathogen: Diplodia spp.
Signs/Symptoms: Dieback of brand tips with dead needles showing uneven lengths
For more information see: UW Plant Disease Facts D0042

Tobacco Rattle

Hosts: Many herbaceous ornamentals and vegetables
Pathogens: Tobacco rattle virus
Signs/Symptoms: Blotchy leaf color; yellow lines, ring spots, or dead spots on leaves; distorted leaf growth
For more information see: UW Plant Disease Facts D0116

For more information on plant problems to watch for in 2026:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

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 Julie Hill, Denise Rocha and Janell Wehr for reviewing this document.

Thanks also to Marissa Wilmot (Septoria leaf spot of lilac), and Anette Phibbs (tobacco rattle) for use of their photos.

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)

Submit additional lawn, landscape, and gardening questions at the Ask a Gardening Question page (https://hort.extension.wisc.edu/ask-a-gardening-question/) of the University of Wisconsin-Madison Division of Extension Horticulture website.

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Problems to Watch for in 2025

April 21, 2025 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/14/2026

D-number: D0136

Scab (Apple and Pear)

Apple Scab

Septoria Leaf Spot of Lilac

Host: Lilac
Pathogen: Septoria sp.
Signs/Symptoms: Dead spots on leaves, potentially leading to complete leaf browning

Aster Yellows

Hosts: Many herbaceous ornamentals and vegetables
Pathogens: Aster yellows phytoplasma
Signs/Symptoms: Yellow/orange/purple leaves, stunted and distorted growth, leafy flowers, brooming
For more information see: UW Garden Facts D0007

Gymnosporangium Rusts

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

Bacterial Canker

Hosts: Stone fruits (cherry, peach, plum)
Pathogen: Pseudomonas syringae
Signs/Symptoms: Masses of sap on affected branches/trunks, branch die back, tree death
For more information see: UW Plant Disease Facts D0009

Powdery Mildew

Septoria Leaf Spot and Early Blight

Rhizosphaera Needle Cast

Diplodia Shoot Blight and Canker

Chlorosis

For more information on plant problems to watch for in 2025:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Julie Hill, Kathy Johnson and Margaret Murphy for reviewing this document.

Thanks also to Marissa Wilmot (Septoria leaf spot of lilac) for use of their photo.

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)

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Problems to Watch for in 2024

April 30, 2024 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/14/2026

D-number: D0135

Winter Injury/Winter Burn

Chlorosis

Blister Canker

Hosts: Apple, crabapple, serviceberry, mountain-ash
Pathogen: Biscogniauxia marginata
Signs/Symptoms: Dark, sunken, cracked areas on trunks with dark, round, flat pads of fungal growth
For more information see: UW Plant Disease Facts D0134

Golden Canker

Host: Pagoda dogwood
Pathogen: Cryptodiaporthe corni
Signs/Symptoms: Dead branches that are gold in color, often with orange spots
For more information see: UW Plant Disease Facts D0055

Diplodia Shoot Blight and Canker

Hosts: Austrian pine, other pines
Pathogen: Diplodia spp.
Signs/Symptoms: Dieback of brand tips with dead needles showing uneven lengths
For more information see: UW Plant Disease Facts D0042

Fire Blight

Hosts: Apple, crabapple, pear, mountain-ash
Pathogen: Erwinia amylovora
Signs/Symptoms: Branch dieback (often with the tip having a shepherd’s crook), eventual tree death
For more information see: UW Plant Disease Facts D0052

Cucumber Mosaic

Hosts: Herbaceous ornamentals and vegetables
Pathogens: Cucumber mosaic virus
Signs/Symptoms: Blotchy light and dark green leaf color, distorted leaf growth
For more information see: UW Plant Disease Facts D0036

Powdery Mildew

Hosts: Herbaceous and woody ornamentals, fruit, vegetables, turf
Pathogens: Miscellaneous powdery mildew fungi
Signs/Symptoms: Powdery white growth on leaves
For more information see: UW Plant Disease Facts D0084/86/87

Red Star Rust

Hosts: Chinese juniper, apple, crabapple
Pathogen: Gymnosporangium yamadae
Signs/Symptoms: Brown blobs with orange gelatinous masses (juniper), red leaf spots (apple, crabapple)
For more information see: UW Plant Disease Facts D0131

Boxwood Blight

Host: Boxwood
Pathogen: Calonectria pseudonaviculata
Signs/Symptoms: Circular, brown leaf spots followed by leaf drop and shrub death
For more information see: UW Plant Disease Facts D0023

Improper Planting

Hosts: Woody trees and shrubs
Pathogen: None
Signs/Symptoms: No root flare at the soil line, girdling roots, frost cracks, canopy thinning, early fall color, branch dieback, tree/shrub decline and death

For more information on plant problems to watch for in 2024:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

References to pesticide products in this publication are for your convenience and are not an endorsement or criticism of one product over similar products. You are responsible for using pesticides according to the manufacturer’s current label directions. Follow directions exactly to protect the environment and people from pesticide exposure. Failure to do so violates the law.

Thanks to Julie Hill, Margaret Murphy and Denise Rocha for reviewing this document.

Thanks also to Serenella Linares (blister canker), Nancy Gregory-University of Maryland (lipstick rust), and David Clement (boxwood blight) for use of their photos.

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)

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Problems to Watch for in 2023

November 13, 2022 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson UW-Madison Plant Pathology

Last Revised: 04/13/2026

D-number: D0132

Lipstick Rust

Host: Chinese juniper, apple, crabapple
Pathogen: Gymnosporangium yamadae
Signs/Symptoms: Brown blobs with orange gelatinous masses (juniper), red leaf spots (apple, crabapple)

Boxwood Blight

Host: Boxwood
Pathogens: Calonectria pseudonaviculata
Signs/Symptoms: Circular, brown leaf spots followed by leaf drop and shrub death
For more information see: UW Plant Disease Facts D0023

Late Blight

Host: Tomato, potato
Pathogen: Phytophthora infestans
Signs/Symptoms: Water-soaked spots on leaves, leathery areas on tomato fruits, rapid plant death
For more information see: UW Plant Disease Facts D0068

Septoria Leaf Spot and Early Blight

Host: Tomato
Pathogens: Septoria lycopersici and Alternaria solani
Signs/Symptoms: Spotting and eventual total collapse of leaves, working from the bottom of the plant up
For more information see: UW Plant Disease Facts D0100/46

Septoria Leaf Spot of Lilac

Host: Lilac
Pathogen: Septoria sp.
Signs/Symptoms: Dead spots on leaves, potentially leading to complete leaf browning

Verticillium Wilt

Hosts: Woody and herbaceous ornamentals, vegetables
Pathogens: Verticillium sp.
Signs/Symptoms: Wilting, branch dieback, plant death
For more information see: UW Plant Disease Facts D0121/D0122

Powdery Mildew

Hosts: Herbaceous and woody ornamentals, fruit, vegetables, turf
Pathogens: Miscellaneous powdery mildew fungi
Signs/Symptoms: Powdery white growth on leaves
For more information see: UW Plant Disease Facts D0084/86/87

Rhizosphaera Needle Cast

Diplodia Shoot Blight and Canker

Chlorosis

Hosts: Pin oak, red maple, birch, azalea, white pine, blueberry
Pathogen: None
Signs/Symptoms: Yellow leaves with dark green veins
For more information see: UW Plant Disease Facts D0030

Improper Planting

For more information on plant problems to watch for:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Lisa Johnson and Carol Shirk for reviewing this document. Thanks also to David Clement (boxwood blight), Nancy Gregory-University of Maryland (lipstick rust), Amanda Gevens (late blight), and Marissa Wilmot (Septoria leaf spot of lilac) for use of their photos.

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)

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Problems to Watch for in 2022

April 28, 2022 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson UW-Madison Plant Pathology

Last Revised: 04/13/2026

D-number: D0132

Boxwood Blight

Lipstick Rust

Host: Chinese juniper, apple, crabapple
Pathogen: Gymnosporangium yamadae
Signs/Symptoms: Brown blobs with orange gelatinous masses (juniper), red leaf spots (apple, crabapple)

Late Blight

Septoria Leaf Spot and Early Blight

Septoria Leaf Spot of Lilac

Host: Lilac
Pathogen: Septoria sp.
Signs/Symptoms: Dead spots on leaves, potentially leading to complete leaf browning

Wood Rots

Hosts: Woody trees and shrubs
Pathogens: Miscellaneous wood rot fungi
Signs/Symptoms: Shelf-like growths on trunks and branches

Canker Diseases

Hosts: Woody trees and shrubs
Pathogens: Miscellaneous canker fungi
Signs/Symptoms: Sunken areas on trunks/branches
For more information see: UW Plant Disease Facts D0027, D0037, D0042, D0055, D0074, D0114

Virus Disaeases

Hosts: All plants, particularly herbaceous ornamentals
Pathogen: Miscellaneous plant viruses
Signs/Symptoms: Blotchy leaf color, growth distortions
For more information see: UW Plant Disease Facts D0036, D0063, D0067, D0115, D0116, D0130

Rhizosphaera Needle Cast

Chlorosis

Improper Planting

For more information on plant problems to watch for:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Julie Hill, Jeannie Manis and Carol Shirk for reviewing this document. Thanks also to David Clement (boxwood blight), Nancy Gregory-University of Maryland (lipstick rust), Amanda Gevens (late blight), Marissa Wilmot (Septoria leaf spot of lilac), and Diane Malchow (wood rots) for use of their photos.

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)

Disease - Vegetable, Quick Reference Guide

Vegetable Disease Quick Reference

June 1, 2021 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/18/2026

D-number: D0120

Septoria Leaf Spot and Early Blight

Host: Tomato
Pathogens: Septoria lycopersicia and Alternaria solani
Signs/Symptoms: Spotting and eventual total collapse of leaves working from the bottom of the plant up
For more information see: UW Garden Facts D0100/D0046

Late Blight

Hosts: Tomato, potato
Pathogen: Phytophthora infestans
Signs/Symptoms: Water-soaked spots on leaves, leathery areas on tomato fruits, rapid plant death
For more information see: UW Garden Facts D0068

Blossom End Rot

Host: Tomato, pepper, eggplant, cucumber, squash
Cause: Calcium deficiency
Signs/Symptoms: Decayed areas on the bottom sides of vegetable fruits
For more information see: UW Garden Facts D0022

Powdery Mildew

Hosts: Any vegetable, particularly vine crops, peas
Pathogens: Miscellaneous powdery mildew fungi
Signs/Symptoms: Powdery white growth on leaves
For more information see: UW Garden Facts D0086

Common Corn Smut

Hosts: Corn
Pathogen: Ustilago maydis
Signs/Symptoms: Pasty white masses on corn ears eventually decomposing into a brown powder
For more information see: UW Garden Facts D0031

Black Rot

Hosts: Crucifers (e.g., cabbage, broccoli, cauliflower)
Pathogen: Xanthomonas campestris pv. campetris
Signs/Symptoms: V-shaped yellow/dead areas on leaves progressing into plant deterioration and death
For more information see: UW Garden Facts D0019

Potato Scab

Hosts: Potato, carrot, beet, other root crops
Pathogen: Streptomyces scabies
Signs/Symptoms: Brown, rough, scab-like areas on tubers and roots
For more information see: UW Garden Facts D0083

Verticillium Wilt

Host: Tomato, pepper, eggplant, potato, vine crops
Pathogen: Verticillium spp.
Signs/Symptoms: Leaf yellowing and wilting of plants followed by eventual plant death
For more information see: UW Garden Facts D0122

Aster Yellows

Host: Carrot
Pathogens: Aster yellows phytoplasma
Signs/Symptoms: Yellow/orange/purple leaves, stunted roots with tufts of white hairy roots
For more information see: UW Garden Facts D0007

Bacterial Wilt

Hosts: Vine crops
Pathogen: Erwinia tracheiphila
Signs/Symptoms: Sectional wilting and eventual death of plants after cucumber beetle feeding
For more information see: UW Garden Facts D0014

Basil Downy Mildew

Host: Basil
Pathogen: Peronospora belbahrii
Signs/Symptoms: Downward-cupped, yellow leaves with purple-gray fuzz on leaf undersurfaces
For more information see: UW Garden Facts D0015

For more information on vegetable 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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Jane Anklam, Vijai Pandian, and Linda Remeschatis for reviewing this document. Thanks also to Amanda Gevens (late blight, black rot, Verticillium wilt), ISU-PIDC (bacterial wilt) and Debbie Roos (basil downy mildew) for use of their photos.

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)

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Quick Reference Guide

Plant Diseases to Watch For in 2021

May 11, 2021 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/13/2026

D-number: D0081

Septoria Leaf Spot and Early Blight

Host: Tomato
Pathogens: Septoria lycopersici and Alternaria solani
Signs/Symptoms: Spotting and eventual total collapse of leaves working from the bottom of the plant up
For more information see: UW Plant Disease Facts D0100/46

Late Blight

Septoria Leaf Spot of Lilac

Host: Lilac
Pathogen: Septoria sp.
Signs/Symptoms: Dead spots on leaves, potentially leading to complete leaf browning

Rhizosphaera Needle Cast

Gymnosporangium Rusts

Elderberry Rust

Hosts: Elderberry
Pathogen: Puccinia sambuci
Signs/Symptoms: Light yellow, powdery growths on branches
For more information see: UW Plant Disease Facts D0049

Scab (Apple and Pear)

Bur Oak Blight

Host: Bur oak
Pathogen: Tubakia iowensis
Signs/Symptoms: Wedge-shaped dead areas on leaves leading to dead leaves that stay attached to trees

Powdery Mildew

Hosts: Herbaceous and woody ornamentals, fruits, vegetables, turf
Pathogens: Miscellaneous powdery mildew fungi
Signs/Symptoms: Powdery white growth on leaves
For more information see: UW Plant Disease Facts D0084/86/87

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

Boxwood Blight

For more information on plant diseases to watch for:

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Margaret Murphy and Denise Worzalla-Rocha for reviewing this document. Thanks also to Amanda Gevens (late blight), Marissa Wilmot (Septoria leaf spot of lilac), Jenell Bindl (elderberry rust), Lina Rodriguez-Salamanca (bur oak blight) and David Clement (boxwood blight) for use of their photos.

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)

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Misc, Quick Reference Guide

Ten Common Plant Diseases/Disorders You Can Diagnose by Eye

April 30, 2021 ddlang

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/16/2026

D-number: D0112

Powdery Mildew

Tar Spot

Hosts: Maples
Pathogen: Rhytisma spp.
Signs/Symptoms: Tarry areas (either solid spots or clusters of small spots) on leaves
For more information see: UW Plant Disease Facts D0110

Peach Leaf Curl

Host: Peach
Pathogen: Taphrina deformans
Signs/Symptoms: Light-green, yellow or purplish-red puckered areas on leaves
For more information see: UW Plant Disease Facts D0076

Sooty Mold

Host: Any plant
Pathogen: Miscellaneous sooty mold fungi
Signs/Symptoms: Powdery black growth on leaves or needles
For more information see: UW Bulletin A2637

Chlorosis

Hosts: Oak, red maple
Cause: Iron or manganese deficiency, often induced by high soil pH
Signs/Symptoms: Yellow leaves with dark green veins
For more information see: UW Plant Disease Facts D0030

Gymnosporangium Rusts

Black Knot

Hosts: Prunus spp. (plum and cherry)
Pathogen: Apiosporina morbosa
Signs/Symptoms: Black poop-like growths on branches
For more information see: UW Plant Disease Facts D0018

Elderberry Rust

Host: Elderberry
Pathogen: Puccinia sambuci
Signs/Symptoms: Light yellow, powdery growths on branches
For more information see: UW Plant Disease Facts D0049

Golden Canker

Host: Pagoda dogwood
Pathogen: Cryptodiaporthe corni
Signs/Symptoms: Gold-colored branches with orange spots
For more information see: UW Plant Disease Facts D0055

Dog Vomit Slime Mold

Hosts: Any plant and on mulch
Cause: Fuligo septica
Signs/Symptoms: Scrambled egg-like masses on mulch or at the base of plants
For more information see: UW Plant Disease Facts D0102

For more information on common plant 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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Mike Maddox and Ann Wied for reviewing this document.

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)

Disease - Broad Leafed Woody Ornamental, Quick Reference Guide

Deciduous Tree Leaf Disease Quick Reference

April 30, 2021 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/09/26

D-number: D0041

Anthracnose

Hosts: Most trees, commonly ash, maple and oak
Pathogens: Gloeosporium spp. as well as other fungi
Signs/Symptoms: Blotchy dead areas on leaves
For more information see: UW Plant Disease Facts D0002

Purple-Bordered Leaf Spot

Host: Amur, Japanese, red, silver and sugar maple
Pathogen: Phyllosticta minima
Signs/Symptoms: Discrete, circular leaf spots with purple borders
For more information see: UW Plant Disease Facts D0089

Tubakia (Actinopelte) Leaf Spot

Hosts: Oak
Pathogen: Tubakia spp. (Actinopelte spp.)
Signs/Symptoms: Discrete circular, or irregular blotchy dead areas on leaves
For more information see: UW Plant Disease Facts D0118

Apple Scab

Hosts: Apple, crabapple, pear, mountain-ash
Pathogen: Venturia inaequalis, V. pirina
Signs/Symptoms: Circular, black leaf spots with feathery edges; eventual leaf loss
For more information see: UW Plant Disease Facts D0004

Gymnosporangium Rusts

Hosts: Apple, crabapple, hawthorn
Pathogens: Gymnosporangium spp.
Signs/Symptoms: Bright yellow-orange, circular leaf spots
For more information see: UW Plant Disease Facts D0058

Powdery Mildew

Hosts: Most deciduous trees
Pathogens: Several genera of powdery mildew fungi
Signs/Symptoms: Uniform/blotchy powdery white areas on upper and lower leaf surfaces
For more information see: UW Plant Disease Facts D0087

Downy Leaf Spot

Hosts: Hickory, walnut
Pathogen: Microstroma juglandis
Signs/Symptoms: Discrete powdery white areas on lower leaf surfaces

Chlorosis

Scorch

Hosts: Most deciduous trees
Cause: Water stress induced by drought, high soil salt content, or other water-limiting factors
Signs/Symptoms: Dead tissue on leaf margins

Tatters

Hosts: Most deciduous trees, but commonly oak
Cause: Possible early season cold injury
Signs/Symptoms: Lacy, tattered-looking leaves
For more information see: UW Plant Disease Facts D0111

For more information on deciduous tree leaf 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.

This Fact Sheet is also available in PDF format:

Full Color PDF

Thanks to Diana Alfuth, Kristin Krokowski, and Patti Nagai for reviewing this document, and to Matt Hanson for supplying the powdery mildew photo

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)

Disease - Needled Woody Ornamental, Quick Reference Guide

Conifer Disease Quick Reference

April 30, 2021 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 04/08/2026

D-number: D0033

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

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

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

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

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.

This Fact Sheet is also available in PDF format:

Full Color PDF

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)