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

Extension Logo

UW Plant Disease Facts

 

Authors:   Brian Hudelson, UW-Madison Plant Pathology
Last Revised:   03/02/2024
D-number:   D0112
 
Powdery Mildew 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
Tar Spot 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 Peach Leaf Curl
Hosts:  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 Sooty Mold
Hosts:  Any plant
Pathogen:   Miscellaneous sooty mold fungi
Signs/Symptoms:  Powdery black growth on leaves or needles
For more information see:       UW Bulletin A2637
Chlorosis 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 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
Black Knot 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 Elderberry Rust
Hosts:  Elderberry
Pathogen:   Puccinia sambuci
Signs/Symptoms:  Light yellow, powdery growths on branches
For more information see:       UW Plant Disease Facts D0049
Golden Canker Golden Canker
Hosts:  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 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 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:

© 2021-2024 the Board of Regents of the University of Wisconsin System doing business as University of Wisconsin-Madison Division of Extension.

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 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.

Submit additional lawn, landscape, and gardening questions at https://hort.extension.wisc.edu/ask-a-gardening-question/.