Vegetable Disease Quick Reference

This article is provided by the UW Plant Disease Diagnostics Clinic.

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
Find more powdery mildew information for…

Late Blight

Hosts:   Tomato, potato
Pathogen:   Phytophthora infestans
Signs/Symptoms:  Water-soaked spots on leaves, leathery areas on tomato fruits, rapid plant death
More information on late blight

Blossom End Rot

Host:   Tomato, pepper, eggplant, cucumber, squash
Cause:   Calcium deficiency
Signs/Symptoms:  Decayed areas on the bottom sides of vegetable fruits
More information on blossom end rot

Powdery Mildew

Hosts:    Any vegetable, particularly vine crops, peas
Pathogens:    Miscellaneous powdery mildew fungi
Signs/Symptoms:  Powdery white growth on leaves
More information on powdery mildew

Common Corn Smut

Hosts:   Corn
Pathogen:   Ustilago maydis
Signs/Symptoms:  Pasty white masses on corn ears eventually decomposing into a brown powder
More information on common corn smut

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
More information on black rot

Potato Scab

Hosts:    Potato, carrot, beet, other root crops
Pathogen:  Streptomyces scabies
Signs/Symptoms:  Brown, rough, scab-like areas on tubers and roots
More information on potato scab

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
More information on verticillium wilt

Aster Yellows

Hosts:    Carrot
Pathogens:    Aster yellows phytoplasma
Signs/Symptoms:  Yellow/orange/purple leaves, stunted roots with tufts of white hairy roots
More information on aster yellows

Bacterial Wilt

Hosts:   Vine crops
Pathogen:   Erwinia tracheiphila
Signs/Symptoms:  Sectional wilting and eventual death of plants after cucumber beetle feeding
More information on bacterial wilt

Basil Downy Mildew

Host:   Basil
Pathogen:   Peronospora belbahrii
Signs/Symptoms:  Downward-cupped, yellow leaves with purple-gray fuzz on leaf undersurfaces
More information on basil downy mildew

UW Plant Disease Facts

Authors:   Brian Hudelson, UW-Madison Plant Pathology
Last Revised:   03/02/2024
D-number:   D0120

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.

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.

Submit a Sample

Download Article