Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 04/18/2025
D-number: D0136
Scab (Apple and Pear) 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
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 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
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 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
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
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
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
For more information on plant problems to watch for in 2025: 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:
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, Kathy Johnson and Margaret Murphy 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.
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 04/27/2024
D-number: D0135
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
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
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 Hosts: 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 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 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
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: 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:
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).
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.
Authors: Brian Hudelson UW-Madison Plant Pathology
Last Revised: 03/01/2024
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 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
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 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:
See https://pddc.wisc.edu/ or contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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, 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.
Authors: Brian Hudelson UW-Madison Plant Pathology
Last Revised: 03/01/2024
D-number: D0132
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
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 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
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 Diseases 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 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
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 D0084
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:
See https://pddc.wisc.edu/ or contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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, 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.
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/02/2024
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 Hosts: 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 https://pddc.wisc.edu/ or contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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.
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/01/2024
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 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 Plant Disease Facts D0068
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 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
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
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) 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
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 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
For more information on plant diseases to watch for:
See https://pddc.wisc.edu/ or contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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, 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.
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/02/2024
D-number: D0112
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 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 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 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 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 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 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 Hosts: Elderberry Pathogen: Puccinia sambuci Signs/Symptoms: Light yellow, powdery growths on branches For more information see: UW Plant Disease Facts D0049
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 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.
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.
Authors: Sue Lueloff and Brian Hudelson, UW-Plant Pathology
Last Revised: 03/02/2024
D-number: D0115
Tobacco mosaic causing a blotchy light and dark coloring (mosaic) of tobacco leaves.
What is tobacco mosaic?
Tobacco mosaic is a common viral disease of worldwide distribution that affects over 200 species of herbaceous and, to a lesser extent, woody plants. Common hosts include tobacco, solanaceous vegetables (e.g., pepper, tomato) and vining vegetables (e.g., cucumber, melon, squash), as well as a wide range of ornamentals (e.g., begonia, coleus, geranium, impatiens, million bells, petunia). The disease has its biggest impact on vegetables, where it can reduce yield and affect quality to the point that commercial crops cannot be marketed.
What does tobacco mosaic look like?
Symptoms of tobacco mosaic vary in type and severity depending on the plant infected, plant age, the variant of the virus involved, and environmental conditions. On leaves, typical symptoms include blotchy light and dark areas (called mosaic); cupping, curling, elongation (strapping), roughening, wrinkling and other growth distortions; and smaller than normal size. Fruits may have a blotchy color, ripen unevenly, be malformed or have an off flavor. Entire infected plants are often stunted. Other viral diseases like cucumber mosaic (see UW Plant Disease Facts D0036, Cucumber Mosaic) can cause symptoms similar to tobacco mosaic. Often, multiple viral diseases can simultaneously affect a single plant. Certain herbicide exposures (see UW Plant Disease Facts D0060, Herbicide Damage), nutrient deficiencies or toxicities, high temperature and even insect feeding can also cause similar symptoms. Proper diagnosis of tobacco mosaic requires lab testing.
Where does tobacco mosaic come from?
Tobacco mosaic is caused by Tobacco mosaic virus (TMV), the first virus ever identified. Numerous variants (strains) of the virus have subsequently been described. TMV survives in infected plants (including viable seeds), as well as in debris from these plants. Plant-based products (most notoriously tobacco products) can harbor the virus. TMV is very stable and can survive for long periods of time; there are reports of TMV surviving and remaining infectious after 50 years in storage at 40°F. Because of its stability, TMV can survive on and be picked up from hands, clothing, gardening tools, work surfaces and any other object (e.g., door knobs) that gardeners may handle.
TMV is highly transmissible and is commonly spread by handling infected plants, then healthy plants. Spread via gardening tools is also very common. No specific insects spread TMV (the way that aphids spread Cucumber mosaic virus). However, bees and chewing insects (e.g., grasshoppers) can transmit TMV through casual contact or their feeding as they move from plant to plant.
Leaf growth distortions caused by tobacco mosaic.
How do I save a plant with tobacco mosaic?
There is no cure for tobacco mosaic. Once infected, plants remain infected for life, and typically the virus spreads throughout the plant from the point of infection. Infected plants and any associated debris should be burned (where allowed by local ordinance) or double-bagged and disposed of in a landfill. DO NOT compost plants with this disease. Thoroughly decontaminate any items that have come into contact with infected plants or their debris by treating them for a minimum of one minute with:
2.75 tablespoons Alconox® (a lab detergent) plus 2.5 tablespoons sodium lauryl sulfate (SLS), also known as sodium dodecyl sulfate (SDS), in one gallon of water, or
14 dry ounces of trisodium phosphate in one gallon of water.
These ingredients can be ordered on the internet. If you decide to use SLS (SDS), be sure to wear gloves, safety goggles and a dust mask, and mix the solution in a well-ventilated area as SLS (SDS) is a known skin and eye irritant. Once treated, rinse items with sufficient water to remove any residues. Also, thoroughly wash your hands with soap and water, and launder any clothing that you wore while disposing of infected plants and debris.
How do I avoid problems with tobacco mosaic virus in the future?
Inspect plants prior to purchase for any symptoms of tobacco mosaic, and DO NOT buy symptomatic plants. Purchase seed from a reputable supplier that routinely inspects their seed-producing plants for symptoms of viral (and other) diseases. If you use tobacco products, DO NOT use them around plants. Also, wash your hands thoroughly with soap and water prior to handling plants, and consider wearing freshly laundered clothing when gardening. Finally, decontaminate (as described above) any items that might harbor TMV to help prevent spread. Even if you do not use tobacco products, routine handwashing and decontamination of gardening tools and other items can help prevent tobacco mosaic from being a problem.
For more information on tobacco mosaic:
Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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).
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 Brenda Dahlfors, Tom German, Jenna LaChance and Diane Lorenz 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.
Authors: Lauren Pryor and Brooke Babler, UW-Madison Plant Pathology
Last Revised: 03/02/2024
D-number: D0117
What is tomato spotted wilt?
Tomato spotted wilt is a common viral disease of worldwide distribution that can affect over 1000 plant species. Economically important hosts include a wide range of vegetables, fruits, field crops, and ornamentals. Many weeds are also potential hosts. Tomato spotted wilt is especially important in greenhouse production where it can cause significant economic losses in horticultural and floral crops. In potato production, tomato spotted wilt is uncommon but of enough concern that routine monitoring for the disease in greenhouse and field settings is warranted.
Leaf spots with concentric rings (left) and stem streaking (right) typical of potato plants due to Tomato spotted wilt. Photos courtesy of G. J. Holmes (left) and Joshua Kunzman (right).
What does tomato spotted wilt look like?
Symptoms of tomato spotted wilt vary widely depending on host species, host variety and when during development a plant is infected. Typical symptoms on leaves include yellow, brown or black ringspots (i.e., ring-like areas of discolored tissue). On some hosts, the ringspots can form a target-like pattern. Distorted leaf growth can also be a typical symptom.
On potato leaves, tomato spotted wilt can lead to necrotic (i.e., dead) areas with or without yellow haloes. These symptoms can resemble symptoms of early blight (see UW Plant Disease Facts D0046, Early Blight). Black streaks on petioles or stems and branch tip dieback are also common symptoms on potato (as well as other hosts). Potato tuber symptoms include surface rings or dark patches, and internal discolored patches, rings, spots or flecks.
Where does tomato spotted wilt come from?
Tomato spotted wilt is caused by Tomato spotted wilt virus (TSWV), which is closely related to Impatiens necrotic spot virus (INSV), the cause of impatiens necrotic spot (see UW Plant Disease Facts D0067, Impatiens Necrotic Spot). TSWV is found in the sap of infected plants and is most commonly spread by thrips (see University of Wisconsin Garden Facts XHT1022, Managing Thrips in Greenhouses). At least eight thrips species can be involved in TSWV transmission. Thrips larvae acquire the virus as they feed on infected plants, then transmit the virus as they move to and feed on healthy plants. Once thrips acquire the virus, they can transmit it for their entire lifespans. The severity of tomato spotted wilt depends on the size and activity of thrips populations at a location, as well as on the number of infected plants (often weeds, but potentially infected potatoes as well) serving as reservoirs for the virus. TSWV can also be transmitted mechanically (e.g., on tools used to trim branches or cut potato tubers), but this method of transmission is much less common than transmission by thrips.
How can I save plants with tomato spotted wilt?
There is no known cure for tomato spotted wilt. Infected plants should be removed and destroyed to eliminate a reservoir for the virus that can subsequently contribute to spread to other plants. Infected plants can be burned (where allowed by local ordinance), deep buried or hot composted.
Surface and internal tuber symptoms due to Tomato spotted wilt . Photos courtesy of Joshua Kunzman.
How can I avoid problems with tomato spotted wilt in the future?
Prevent introducing TSWV and thrips into your greenhouse by carefully inspecting any new plants for potential problems. Test suspect plants for TSWV using dipstick tests [available from Agdia, Inc. (www.agdia.com)] or by submitting a sample to the UW-Madison Plant Disease Diagnostics Clinic (pddc.wisc.edu). Remove and dispose of any infected plants.
To prevent new infections via thrips, remove weeds in and outside of greenhouses to eliminate TSWV and thrips reservoirs. Place 400-mesh screens on vents to limit thrips movement. Also limit thrips movement on clothing by avoiding colors (e.g., pink, blue, yellow, white or green) that can attract thrips. Monitor for thrips using blue and yellow sticky cards placed above plants throughout the greenhouse and near doors and vents. Use chemical and/or biological control products to control thrips. See University of Wisconsin Garden Facts XHT1022, Managing Thrips in Greenhouses, for details on what products to use and when to use them. Multiple applications will likely be necessary because thrips eggs are not killed by insecticides. If you find plants that you suspect are infected with TSWV, remove and dispose of these plants immediately.
To prevent mechanical transmission of TSWV, be sure to routinely decontaminate any items (e.g., pruners, knives, pots, work surfaces) that come into contact with plants by treating them for a minimum of one minute with a solution of one of the following:
2.75 tablespoons Alconox® (a type of lab detergent) plus 2.5 tablespoons sodium dodecyl sulfate (SDS) [also known as sodium lauryl sulfate (SLS)] in one gallon of water, or
14 dry ounces of trisodium phosphate in one gallon of water.
In field settings, tomato spotted wilt does not appear to be a significant problem on potato (although it can be a significant problem on other crops). Use of resistant or tolerant potato varieties may reduce yield loses, but unfortunately there is little information on which potato varieties are resistant/tolerant to the disease. Removing symptomatic plants can reduce potential reservoirs of TSWV, but may not be feasible. More important in field settings may be to keep weeds under control. Current research suggests that TSWV does not persist long-term in the field unless there are perennial weeds to serve as TSWV reservoirs.
For more information on tomato spotted wilt:
Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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).
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 Tom German, Clover Spacek and Denise Worzalla-Rocha 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.
Authors: Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/01/2024
D-number: D0090
What is Ralstonia wilt?
Ralstonia wilt (also sometimes known as Southern wilt) is a typically lethal disease that affects over 250 plants in over 40 plant families. Susceptible greenhouse-grown ornamentals include, but are not limited to, plants in the genera Capsicum, Cosmos, Cyclamen, Dahlia, Fuschsia, Gerbera, Hydrangea, Impatiens, Lantana,Nasturtium and Pelargonium. Vegetables such as eggplant, pepper, potato and tomato, as well as tobacco, are also susceptible. Ralstonia wilt was first reported on geraniums (Pelargonium spp.) in Wisconsin in 1999. In 2020, the disease was reported on Fantasia® ‘Pink Flare’ geraniums in Michigan. Potentially infected ‘Pink Flare’ geraniums were also distributed to 38 other states including Wisconsin.
Yellowing and wilting characteristic of Ralstonia wilt. Photo courtesy of WI DATCP
What does Ralstonia wilt look like?
Symptoms of Ralstonia wilt in geraniums are similar to those associated with bacterial blight (caused by Xanthomonas campestris pv. pelargonii). Initially, lower leaves of infected plants yellow and wilt, then die. Yellowing and death of upper leaves follow. Symptoms may initially occur on only one side of the plant. Internally, the water-conducting tissue of the plant browns, and then the entire stem rots from the inside out. Eventually, infected plants die.
Where does Ralstonia wilt come from?
Ralstonia wilt is caused by the bacterium Ralstonia solanacearum (formerly Pseudomonas solanacearum). This bacterium is commonly found in tropical, sub-tropical and warm temperate climates, but it is not believed to survive cold temperatures such as those typical of Wisconsin winters. The bacterium can be moved in symptomless plants or cuttings, or in contaminated soil and plant debris (where the pathogen can remain dormant for many years). Several subgroups (i.e., races and biovars) of R. solanacearum have been recognized, each with a different host range. R. solanacearum race 3, biovar 2 is of particular concern because it causes a serious disease of potato called brown rot. In addition, this race/biovar has been listed as a select agent by the U.S. government and is considered to have potential to be developed as a bioterrorist weapon against U.S. agriculture.
How do I save plants with Ralstonia wilt?
There are no known treatments that will save plants affected by Ralstonia wilt. If you believe your plants are suffering from this disease, immediately contact your local department of agriculture or county Extension agriculture or horticulture agent to arrange for confirmatory testing. If you live in Wisconsin, you can contact the UW-Madison Plant Disease Diagnostics Clinic (see below for contact information) for assistance. If your plants test positive for R. solanacearum race 3, biovar 2 the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) must be notified and this organization will provide guidance on proper disposal of contaminated plants, as well as decontamination of greenhouses or other sites where contaminated plants have been grown.
How do I avoid problems with Ralstonia wilt in the future?
Start by purchasing and growing pathogen-free plant cuttings. Keep plants from different suppliers physically separated by at least four feet to minimize the risk of cross contamination should a shipment of plants prove to be contaminated. Because R. solanacearum is easily moved with soil or water, minimize splashing or any other movement of water or soil from plant to plant when watering. When taking cuttings or trimming plants, be sure to clean cutting tools between cuts using an approved disinfectant. For a complete list of such products, contact the UW-Madison Plant Disease Diagnostics Clinic (see below for contact information). Also wear disposable gloves (nitrile are best) when handling plants, and change gloves between working with different geranium varieties. This will minimize the possibility of moving R. solanacearum by touch. If gloves are not available, wash your hands frequently and thoroughly (especially between geranium varieties) with lots of soap and water or with an alcohol-based hand sanitizer. Remove and destroy weeds or weed debris as these can harbor the pathogen. Finally, do not grow plants in a greenhouse where the disease has occurred unless it has been properly decontaminated.
For more information on Ralstonia wilt:
Contact the University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) at (608) 262-2863 or pddc@wisc.edu.
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).
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 Alemu Mengistu, Julie Tans-Kersten and Laurie Weiss 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.