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.
© 2021-2026 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 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)
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.