All posts by hudelson

Disease - Herbaceous Ornamental, Disease - Vegetable

White Mold

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Ann Joy and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0125

Stem cankers, cottony mycelia and sclerotia (see arrows) of white mold on snap beans.

What is white mold?

White mold, also known as Sclerotinia stem rot, is a serious and typically lethal fungal disease that affects over 400 species of plants in many plant families. White mold causes severe damage in commercially grown snap beans, kidney beans, lima beans and soybeans (see UW Plant Disease Facts D0099, Sclerotinia Stem Rot), as well as commercially grown sunflowers. White mold also can be a serious problem in home vegetable gardens on tomatoes, potatoes, cucurbits (e.g., cucumber, pumpkin and squash), carrots, lettuce, celery, brassicas (e.g., cabbage, broccoli, and cauliflower), basil, and rosemary. White mold is a common disease on many annual and perennial ornamentals as well.

What does white mold look like?

Symptoms of white mold vary depending on the plant infected. White mold can lead to crown and stem cankers (i.e., localized infected areas), root rots, wilts, damping-off of seedlings, and blossom and fruit rots. Plants affected by white mold can wilt rapidly due to stem-girdling cankers at or near the soil line. Brown spots can appear on flower petals and buds. Cottony masses of fungal threads (called mycelia) may appear on stems or on nearby soil. Hard, irregularly-shaped masses (called sclerotia) develop within or on the surface of infected plants. The sclerotia are white at first and then turn dark brown or black as they mature, resembling mouse or rat droppings.

Where does white mold come from?

White mold is caused by several species of the fungus Sclerotinia, most commonly Sclerotinia sclerotiorum. White mold fungi overwinter as sclerotia in dead plant material or in infested soil. Sclerotia can survive in soil for at least five years. During periods of cool, wet or humid weather, sclerotia germinate to form either fungal threads (called hyphae) or tiny, mushroom-like spore-producing structures (called apothecia). Apothecia can release millions of spores over a period of several days. Spores are dispersed primarily by wind, but also by rainsplash and insects. Both spores and hyphae can infect plant tissue, with infection often occurring through dead or declining plant parts (e.g., flowers, leaves), and then spreading to healthy tissue. Infections may also occur through healthy plant parts that are growing near or in contact with the soil. In some plants, seeds can be contaminated by sclerotia or mycelia of white mold fungi.

White mold can be destructive on ornamentals such as Liatris.

How do I save plants with white mold?

White mold is difficult to manage once infections have occurred. Prune four to five inches below obviously disease tissue or remove entire plants if they are severely affected. DO NOT compost these materials because of the risk of spreading white mold fungi via long-lived sclerotia. Burn these materials instead.

How do I avoid problems with white mold in the future?

Check seed for sclerotia and remove these structures if you find them. Make sure your soils are well-drained, and avoid overwatering as well as frequent, light watering. DO NOT overhead water (e.g., with a sprinkler). Instead water deeply early in the day with a drip or soaker hose. Promote good air circulation in your garden so that plants more rapidly dry when they do get wet (e.g., from natural rain). Better air circulation can be achieved by choosing cultivars or varieties of plants that have a more open growth form, by spacing plants farther apart, by avoiding excessive use of nitrogen fertilizers (which can promote excessive production of lush, thick foliage), and by keeping weeds under control. Weed control also eliminates potential alternate hosts that white mold fungi can infect. As leaves and flowers or your plants naturally wither and die, remove them, as well as any other plant debris that may harbor white mold fungi. Finally, in beds where severe cases of white mold have occurred, consider removing and replacing infested soil.

For more information on white mold:

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).

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 R. Vaughan James, Karen Delahaut & Laura Jull 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.qa.webhosting.cals.wisc.edu.

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

Disease - Needled Woody Ornamental, Pest Alerts

Weir’s Cushion Rust of Spruces – Pest Alert

August 19, 2015 hudelson

UW Plant Disease Facts

Pest Alert

Authors: Glen R. Stanosz, UW Madison Plant Pathology, and Forest Ecology and Management

Last Revised: 03/02/2024

D-number: D0124

What is Weir’s cushion rust?

Weir’s cushion rust is a needle disease that disfigures and reduces growth of spruce trees (Picea spp.) of all ages. This disease has been known in both eastern and western regions of the United States, but was recognized in Wisconsin for the first time in 2002.

Yellow spots and bands in winter on spruce shoots affected by Weir's cushion rust. — Yellow spots and bands in winter on spruce shoots affected by Weir’s cushion rust.

What does Weir’s cushion rust look like?

Needles on current year’s shoots affected by Weir’s cushion rust may develop yellow spots or bands in the summer and fall. These spots and bands may intensify to give needles a bright “green and gold” appearance the following spring, when tiny blister-like pustules (a type of fungal reproductive structure) develop in the yellow areas. Microscopic examination of these pustules is required for diagnosis of the disease. Affected one-year-old needles continue to yellow, turn brown, and fall off as the spring and summer progress. Trees badly damaged by Weir’s cushion rust will have thin crowns due to repeated loss of the previous year’s needles.

Where does Weir’s cushion rust come from?

Weir’s cushion rust results from colonization of spruce needles by the fungus Ceropsora weirii (formerly Chrysomyxa weirii). This fungus overwinters in needles infected during the previous growing season. In late summer, or more typically the following spring, C. weirii produces spores in the pustules that develop on the needles. These spores can be blown by wind or splashed by rain to newly emerging needles on the same tree or other trees. Spore germination is followed by infection of young needles.

Can I save a tree affected by Weir’s cushion rust?

Apply fungicides containing chlorothalonil to trees affected by Weir’s cushion rust to prevent new needle infections. Make the first application when 10% of the buds have broken and two additional applications at seven to 10 day intervals thereafter. Fungicide applications do not kill the fungus in needles that are already infected, so be sure to begin applications promptly and complete the spray program, to ensure thorough coverage and protection of new foliage. Please be sure to read and follow all fungicide label instructions to ensure that you use the product in the safest and most effective manner possible. Needles infected by C. weirii eventually die. The fungus does not continue to live or produce spores on these dead needles. Therefore, destruction of dead needles is not necessary.

How do I avoid Weir’s cushion rust in the future?

DO NOT accept and plant landscape or nursery stock affected by Weir’s cushion rust. Inspect established spruce trees (in both landscape and nursery settings) in late summer and fall for evidence of Weir’s cushion rust (e.g., yellow spots and bands on the current year’s needles). Inspect suspect trees again in spring for these symptoms, as well as pustules of C. weirii on the previous year’s needles. In nurseries, move affected trees to areas where the disease is not already present. Use fungicide applications to prevent establishment of the fungus on new trees or in previously unaffected nurseries and landscapes.

For more information on Weir’s cushion rust:

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 Brian Hudelson 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.qa.webhosting.cals.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental, Disease - Herbaceous Ornamental

Volutella Blight

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Gina Muscato and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0123

What is Volutella blight?

Volutella blight is a common and potentially lethal disease of Japanese pachysandra (Pachysandra terminalis), an evergreen, semi-woody groundcover that is grown in shade gardens throughout hardiness zones 4 and 5 in Wisconsin. Volutella blight can severely limit the aesthetic appeal of pachysandra wherever it is grown.

Volutella blight often starts as lesions on individual leaves, but can eventually kill groups of pachysandra plants.

What does Volutella blight look like?

Volutella blight begins as discrete, water-soaked areas (lesions) on pachysandra leaves and stems that eventually turn black/brown and become necrotic (i.e., die). Lesions can be circular, oval or irregular in shape, and may have darker margins. Distinct concentric rings also may be visible in the lesions. Lesions on a single leaf can merge and cause the collapse of the entire leaf, while stem lesions can lead to the collapse of an entire pachysandra plant. When severe, Volutella blight can kill large patches of a pachysandra planting.

Where does Volutella blight come from?

Volutella blight is caused by the fungus Volutella pachysandricola which survives in infected plants, as well as on and in pachysandra plant debris. During wet weather, this fungus produces masses of light-orange to pink fungal spores and hyphae (i.e., fungal threads) that may be visible to the naked eye.

How do I save a plant with Volutella blight?

Remove diseased leaves, as well as any leaf debris, and prune back or dig up plants with stem infections. Dispose of this material by burning (where allowed by local ordinance), burying or hot composting it. Be sure to prune only when plants are dry to minimize the spread of the causal fungus. Be sure to clean your pruning tools between cuts by treating them for at least 30 seconds in a 10% bleach solution or (preferably due its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). If you use bleach, be sure to thoroughly rinse and oil tools after you are done pruning to prevent rusting.

When disease is severe, follow leaf and plant removal by treating remaining plants with one or more applications of a broad-spectrum fungicide (e.g., one containing chlorothalonil). Select a product that is labeled for use on pachysandra, and follow all label instructions to ensure that you apply the product in the safest and most effective way possible.

How do I avoid problems with Volutella blight in the future?

V. pachysandricola is a somewhat opportunistic pathogen, most often causing problems on pachysandra that is weakened or under stress. Therefore, reduce any stresses where possible. Reduce stress due to overexposure to sun by always planting pachysandra in a shady area. DO NOT overcrowd new plantings, and thin existing beds to not only reduce stress from competition but also to promote good air flow and rapid drying of plants. Dry plants are less likely to become infected than plants that stay wet for extended periods. To prevent water stress during the summer and reduce winter injury over the winter, established pachysandra should receive approximately one inch of water per week during the growing season up until the point where there is snowfall or the ground freezes. Newly planted pachysandra should receive approximately two inches of water per week. If there is insufficient rain, water plants using a soaker or drip hose. Minimize salt usage on sidewalks or driveways near pachysandra beds to limit salt injury that can predispose plants to infection. Control insect pests and avoid over-pruning of pachysandra to limit wounds that might serve as entry points for V. pachysandricola.

For more information on Volutella blight:

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, Laura Jull and Christine Regester 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.qa.webhosting.cals.wisc.edu.

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

Disease - Vegetable

Verticillium Wilt of Vegetables

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Ken Frost* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0122

What is Verticillium wilt?

Verticillium wilt is a typically fatal disease that affects a wide range of vegetable crops in Wisconsin. Vegetables commonly and severely affected by Verticillium wilt include tomato, potato, pepper, eggplant, cucumber, muskmelon, pumpkin and watermelon. Other vegetables such as asparagus, bean, beet, broccoli, Brussels sprouts, cabbage, cauliflower, celery, chive, collards, garlic, kale, kohlrabi, leek, lettuce, mustard, onion, parsley, peas, radish, rutabaga, spinach and turnip are susceptible to Verticillium wilt, but show less severe symptoms. Some vegetables, such as sweet corn are immune to the disease. Many woody and herbaceous ornamentals are also susceptible to Verticillium wilt (see also UW Plant Disease Facts D0121 Verticillium Wilt of Trees and Shrubs).

A blotchy yellow leaf color can be an initial symptom of Verticillium wilt on eggplant. (photo courtesy of Amanda Gevens)

What does Verticillium wilt look like?

Initial symptoms of Verticillium wilt include sudden yellowing of foliage, typically first appearing on one side of a plant. These leaves then wilt and die. Oftentimes, symptoms mimic the natural aging process of leaves. Eventually however, the entire plant becomes affected and dies. By peeling away the outer layers of affected branches or vines, you may observe brown streaking in the vascular (water-conducting) tissue. Vascular browning is common in tomato and potato plants.

Where does Verticillium wilt come from?

Verticillium wilt is caused primarily by two fungi, Verticillium dahliae and Verticillium albo-atrum. These fungi are commonly found in Wisconsin soils. V. dahliae and V. albo-atrum have wide host ranges including many common weeds, such as ragweed, cocklebur, and velvetleaf. Susceptible plants and their debris can serve as an overwintering site for these fungi. In potato, root lesion nematodes (Pratylenchus spp.) can contribute to the development of Verticillium wilt. However, the role of these nematodes in Verticillium wilt development in other vegetable crops is not well understood.

How do I save a plant with Verticillium wilt?

Vegetables infected with Verticillium cannot be cured and will eventually die. However, you can extend the life of infected plants by fertilizing and watering them properly. Fertilization should be based on a soil nutrient test and should be tailored to the specific vegetables being grown. Most vegetables require approximately one inch of water per week. If natural rains are not sufficient, then supplemental water should be applied using a soaker or drip hose.

Verticillium wilt eventually leads to wilting and plant death. (photo courtesy of Amanda Gevens)

How do I avoid problems with Verticillium wilt in the future?

Do not repeatedly grow crops that are highly susceptible to Verticillium wilt in the same area of your garden each year. Try to rotate highly susceptible crops with other less susceptible crops. See University of Wisconsin Garden Facts XHT1210, Using Crop Rotation in the Home Vegetable Garden, for details on this process. Also, try to plant vegetable varieties that are resistant to Verticillium wilt. In particular, many modern tomato varieties are resistant to the disease. Watch for varieties with the letter “V” after the variety name. If Verticillium wilt resistant varieties of your favorite vegetables are not available, select varieties that mature early. Early maturing varieties are more likely to produce usable vegetables before they eventually succumb to the disease than late maturing varieties.

In addition to using resistant varieties, try to eliminate sources of Verticillium in your garden. Keep broadleaf weeds under control, as these plants are often susceptible to Verticillium wilt and can serve as a reservoir for the fungus. DO NOT use mulches that may have been produced from trees (e.g., maple and ash trees) that are susceptible to Verticillium wilt, and immediately collect and discard leaves that have fallen from symptomatic trees. Also, remove and discard debris from susceptible vegetable plants. Burn (where allowed by local ordinance) or landfill infected plants and infested plant debris. DO NOT bury or compost these materials. Finally, decontaminate any gardening items (e.g., shovels, hoes, plant stakes, pots, working surfaces, etc.) that may have come into contact with Verticillium to prevent spread of the fungus. Rinse these items with water to remove clinging soil, then treat them for at least 30 seconds with a 10% bleach solution or (preferable for metal tools due its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). If you use bleach, be sure to thoroughly rinse and oil metal tools after gardening to prevent rusting.

For more information on Verticillium wilt:

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

* Completed as partial fulfillment of the requirements for Plant Pathology 875 – Plant Disease Diagnostics Clinic Internship at the University of Wisconsin Madison.

Thanks to Rosemarie Bugs, Amanda Gevens and Chris Parise 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.qa.webhosting.cals.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental

Verticillium Wilt of Trees and Shrubs

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0121

Sudden yellowing, wilting and death of leaves and branches, particularly starting in one section of a tree or shrub, is a typical symptom of Verticillium wilt.

What is Verticillium wilt?

Verticillium wilt is a typically fatal disease that affects a wide range of deciduous woody ornamentals in Wisconsin. Trees most commonly and severely affected are maple and ash. Other trees and shrubs such as barberry, catalpa, elm, lilac, linden, smoke-tree and redbud are also susceptible. In addition, many herbaceous ornamentals, as well as vegetable crops (see UW Plant Disease Facts D0122 Vertcillium Wilt of Vegetables), can be affected by this disease.

What does Verticillium wilt look like?

The first signs of Verticillium wilt that you may notice are individual branches that suddenly wilt and die. Affected branches may occur on one side of the tree or may be scattered throughout the tree. If you carefully peel away the bark of these branches, you may see brown or green streaking in the sapwood just under the bark. Streaking is common in trees such as maple or redbud, but often is not visible in ash and lilac.

Where does Verticillium wilt come from?

Verticillium wilt is caused primarily by two fungi, Verticillium dahliae and Verticillium albo-atrum. These fungi are commonly found in Wisconsin soils and in roots, branches and leaves of infected plants. These fungi enter trees and shrubs through their roots and grow in the xylem (i.e., the water-conducting tissue) of plants where they lead to blockage of water movement. This lack of water movement is what eventually leads to wilting.

How do I save a tree or shrub with Verticillium wilt?

Trees and shrubs infected with Verticillium cannot be cured and will likely eventually die. However, you can extend the life of your plants by making sure that you water and fertilize them properly. Make sure established trees and shrubs receive approximately one inch of water per week. If rainfall is insufficient, use a drip or soaker hose to apply supplemental water near the drip line of the plants (i.e., the edges of where the branches extend). Fertilize trees as needed, but be sure to base any fertilization on a soil nutrient test. To prevent competition for water and nutrients, remove grass within the drip line of your trees and shrubs, and replace it with shredded hardwood, pine or cedar mulch. On heavy, clay soils, use one to two inches of mulch. On lighter, sandy soils, use three to four inches of mulch. Be sure to keep mulch four inches from the main trunks and crowns of trees and shrubs.

Internal streaking in the sapwood of a branch is typical of Verticillium wilt.

In addition, prune out dead branches as they occur. Dispose of these branches by burning (where allowed by local ordinance) or landfilling them. DO NOT bury or compost these branches. Be sure to clean your pruning tools between cuts by treating them for at least 30 seconds in a 10% bleach solution or (preferably due its less corrosive properties) 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). Decontaminating tools will help prevent spread of Verticillium from branch to branch, or more importantly from tree to tree, as you prune. ). If you use bleach, be sure to thoroughly rinse and oil tools after you are done pruning to prevent rusting.

How do I avoid problems with How do I avoid problems with Verticillium wilt in the future?

The best way to avoid Verticillium wilt is to plant trees and shrubs that are immune or resistant. Resistant deciduous trees and shrubs [as adapted from Diseases of Trees and Shrubs, Second Edition by W. Sinclair and H. H. Lyon (Comstock Publishing Associates, 2005)] include apple, aspen, azalea, beech, birch, butternut, crabapple, dogwood, flowering quince, ginkgo, hackberry, hawthorn, hickory, holly, honeylocust, katsura tree, mountain-ash, oak, pear, poplar, sweetgum, sycamore, walnut, and willow. Conifers (e.g., pines, spruces and firs) appear to be immune to the disease. Also, DO NOT use mulches that may have been produced from infected trees or that are of unknown composition. Finally, immediately collect and discard leaves that have fallen from symptomatic trees. Both mulch and leaves are potential sources of Verticillium.

For more information on Verticillium wilt:

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 Jean Ferdinandsen, Patti Nagai and Scott Reuss 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.qa.webhosting.cals.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental

Tubakia (Actinopelte) Leaf Spot

August 18, 2015 hudelson

UW Plant Disease Facts

Authors: Gina Foreman* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0118

Symptoms of Tubakia (Actinopelte) leaf spot on oak.

What is Tubakia (Actinopelte) leaf spot?

Tubakia leaf spot (formerly Actinopelte leaf spot) is a common late-season leaf disease of oaks. All species of oak appear to be susceptible to the disease, but oaks in the red oak group (i.e., oaks with pointed-lobed leaves) such as black, red and pin oak) appear to be most susceptible.

What does Tubakia (Actinopelte) leaf spot look like?

People often confuse symptoms of Tubakia leaf spot with those of oak anthracnose (see UW Plant Disease Facts D0002, Anthracnose). However anthracnose tends to develop earlier, in the cooler part of the growing season (May and June); Tubakia leaf spot tends to develop later, during the warmer summer months (July and August). Initial symptoms of Tubakia leaf spot include small to large dark brown or reddish-brown spots on leaves. Spotting can occur on leaf veins, and death of the veins leads to collapse of leaf tissue beyond the point of infection. Small twig cankers may also form. When the disease is severe, Tubakia leaf spot can cause early defoliation of oaks. However, disease usually develops late enough in the growing season that no long-term adverse effects on tree health occur.

Where does Tubakia (Actinopelte) leaf spot come from?

Tubakia leaf spot is caused by the fungus Tubakia dryina (formerly Actinopelte dryina), a fungus that is most likely a fungus “complex” (i.e., a group of several distinct, but closely related fungi). Tubakia overwinters in infected twigs, and in dead leaves that hang from the tree or are scattered on the ground. Spores of the fungus are easily spread by wind and rain splash.

How do I save a tree with Tubakia (Actinopelte) leaf spot?

DO NOT panic! In most cases Tubakia leaf spot is a cosmetic disease. The disease will make a tree look a little ragged, but will not kill the tree. DO NOT attempt to use fungicide sprays to control this disease.

How do I avoid problems with Tubakia (Actinopelte) leaf spot in the future?

Reduce the amount of Tubakia dryina in your landscape by removing and disposing of fallen, infected leaves by burning (where allowed by local ordinance), burying or hot composting them. When composting, make sure that the pile reaches high temperature (approximately 140°F), and be sure to routinely turn the pile, so that leaves on the outside of the pile eventually end up in the center of the pile. The combination of high temperature and leaf decay helps eliminate the Tubakia leaf spot fungus. Also, maintain good tree vigor. Established trees require approximately one inch of water per week from natural rain or supplemental watering at the drip line of the tree (i.e., the edge of where the branches extend). Fertilize trees as needed based on soil nutrient testing.

For more information on Tubakia (Actinopelte) leaf spot:

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

* Completed as partial fulfillment of the requirements for a MS in Plant Pathology at the University of Wisconsin Madison.

Thanks to Karen Delahaut, Ann Joy, and Phil Pellitteri 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.qa.webhosting.cals.wisc.edu.

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

Disease - Herbaceous Ornamental

Tobacco Rattle

August 18, 2015 hudelson

UW Plant Disease Facts

Authors: Rachel Zwieg* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0116

What is tobacco rattle?

Tobacco rattle is a common and potentially serious viral disease that affects a variety of herbaceous ornamentals including, but not limited to, astilbe, bleeding heart, coral bells, daffodil, epimedium, gladiolus, hyacinth, marigold, tulip and vinca. Tobacco rattle can also affect vegetable crops such as beans, beets, peppers, potatoes, and spinach. On potatoes, the disease is referred to as corky ring spot (see UW Plant Disease Facts D0034, Corky Ring Spot) and can make affected potato tubers unmarketable.

Tobacco rattle virus-infected plants often have leaves with yellow line patterns.

What does tobacco rattle look like?

Symptoms of tobacco rattle can vary depending on the plant species or variety/cultivar affected, and depending on environmental conditions. Infected plants may exhibit mottling (i.e., blotchy light and dark discoloration of leaf tissue), yellow ring spots or line patterns, localized chlorotic (i.e., yellow) spots or streaks, necrotic lesions (i.e., dead spots), or leaves with notches. Leaf discoloration symptoms are often quite attractive and can be misidentified as variegation, a natural variation in leaf color due to plant genetics. Plants that become infected with TRV at a young age can exhibit a variety of leaf and stem deformities. In potato, the disease typically manifests itself as a series of necrotic, corky spots, arcs or rings in tuber tissue.

Where does tobacco rattle come from?

Tobacco rattle is caused by the Tobacco rattle virus (TRV). The virus is often introduced into a landscape in infected plants. Once established in a location, the virus can be spread to other plants by stubby-root nematodes, a group of microscopic, worm-like organisms in the genera Trichodorus and Paratrichdorus. These nematodes feed on the roots of infected plants, acquiring TRV, then move to non-infected plants where their subsequent feeding spreads the virus. TRV also can be spread from plant to plant mechanically when pruning tools (e.g., shovels, trowels, knives, pruners) that are used to trim or divide plants become contaminated with the sap from infected plants. Grafting is another means by which the virus can be transmitted. Finally, TRV can be found in seeds from infected plants.

How do I save a plant with tobacco rattle?

Once plants have become infected with TRV, they remain infected indefinitely. Infected plant cannot be treated in any way to eliminate the virus. They should be removed and disposed of by burning (where allowed by local ordinance), burying or hot composting.

Ringspot symptoms on epimedium due to tobacco rattle virus. Photo courtesy of Anette Philbbs of the WI DATCP.

How do I avoid problems with tobacco rattle in the future?

The best way to prevent problems with tobacco rattle is to grow plants that are not susceptible to TRV. Such plants include, but are not limited to, annual phlox, carnation, sweet William, zinnia and plants in the genus Datura (e.g., devil’s trumpet, downy thorn-apple, zombie cucumber). Before buying either annual or perennial ornamentals, carefully inspect plants susceptible to TRV for symptoms caused by the virus. DO NOT buy symptomatic plants. Keep in mind however, that infected plants may not show symptoms at all times.

To prevent mechanical spread of TRV when pruning or dividing plants, decontaminate tools 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 tools with sufficient water to remove any residues. Also, when working with plants, thoroughly wash your hands on a regular basis with soap and water to deactivate any of the virus you may pick up on your hands.

Control of the nematodes that transmit TRV is not practical in home garden settings and is not recommended.

For more information on tobacco rattle:

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

* Completed as partial fulfillment of the requirements for the Horticulture track of the Farm and Industry Short Course program at the University of Wisconsin Madison.

Thanks to Amy Charkowski, Russell Groves and Tom German for reviewing this document, and to Anette Phibbs of the Wisconsin Department of Agriculture, Trade and Consumer Protection for providing the photo.

A complete inventory of UW Plant Disease Facts is available at the University of Wisconsin-Madison Plant Disease Diagnostics Clinic website: https://pddc.qa.webhosting.cals.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental, Pest Alerts

Thousand Cankers Disease – Pest Alert

August 18, 2015 hudelson

UW Plant Disease Facts

Pest Alert

Authors: Karen Schlichter*, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0113

What is thousand cankers disease?

Thousand cankers disease (TCD) is a serious disease of black walnut (Juglans nigra), a tree native to Wisconsin. TCD has not yet been reported in Wisconsin, but has been found in the western United States where it was first described in 2008. TCD more recently has been reported in the eastern U.S. in Indiana, Maryland, North Carolina, Ohio, Pennsylvania, Tennessee, and Virginia. TCD has been fatal to black walnut in all known cases. Other walnut species found in the western U.S. [e.g., California walnut (Juglans californica) and Arizona walnut (Juglans major)] appear to be much less susceptible. Butternut (Juglans cinerea), another tree native to Wisconsin, is also known to be susceptible.

Discoloration and tunneling under the bark of a walnut branch associated with thousand cankers disease leads to disruption of water and nutrient movement and eventual tree death. (Photo courtesy of Karen Snover-Clift, Cornell University, Bugwood.org)

What does thousand cankers disease look like?

The first symptom of TCD is a yellowing of the leaves starting at the top of a walnut tree. Eventually lower leaves yellow and branches die. Death of the entire tree soon follows. Branches on trees with TCD have tiny holes (about the size of a pencil tip) made by a small beetle, the walnut twig beetle (Pityophthorus juglandis), that is involved in the disease. Beneath the bark of symptomatic branches, well-defined dark black or brown cankers (i.e., diseased areas) form. Cankers eventually merge, disrupting movement of water and nutrients in the tree, leading to tree death.

Where does thousand cankers disease come from?

Thousand cankers disease is caused by a combined effects of a fungus (Geosmithia morbida) and the walnut twig beetle. The insect carries the fungus on its body and introduces the fungus into a walnut tree as it tunnels into the bark to feed. Walnut twig beetles spread the fungus locally as they move from tree to tree to feed. The fungus does not appear to spread from tree to tree by root grafts. Longer distance dispersal of the insect and fungus is possible when walnut seedlings, walnut firewood, and walnut wood products are moved by human activities. Walnut fruits have not been reported as a source of the insect or fungus.

How can I save a tree with thousand cankers disease?

At this time, there are no formal recommendations for managing TCD. Researchers are attempting to develop treatment methods, including use of insecticides, fungicides and nutrient management, to help prolong the life of infected trees. Because TCD has not yet been reported in Wisconsin, the most important management strategy at this time is prevention.

How can I avoid problems with thousand cankers disease in the future?

The best way to prevent the spread of TCD (as well as other tree pests and diseases)s to not move firewood! For information about the restrictions on moving firewood in Wisconsin visit the Wisconsin Department of Natural Resources website at http://dnr.wi.gov/topic/invasives/firewood.html. Also be cautious about moving walnut transplants or other walnut products (especially those with the bark still attached), particularly if they are coming from an area where TCD has been reported.

For more information on thousand cankers disease:

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

*Completed as partial fulfillment of the requirements for Plant Pathology 558 at the University of Wisconsin Madison.

Thanks to Diana Alfuth, Cory Bender, Laura Jull, Phil Pellitteri, Katie Schlichter and Wendy Kramper 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.qa.webhosting.cals.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental

Tatters

August 18, 2015 hudelson

UW Plant Disease Facts

Authors: Rachel Leisso* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0111

Leaves with tatters appear shredded, or as if damaged by leaf-feeding insects.

What is tatters?

Tatters is a leaf disorder affecting primarily members of the white oak group of oaks (i.e., oaks with leaves with rounded lobes) including bur, white and swamp white oaks. Members of the red oak group of oaks (i.e., oaks with leaves with pointed lobes), including red, black, pin and shingle oaks, as well as other types of trees, rarely display the disorder. Tatters was first documented in Iowa, Indiana and Ohio in the 1980’s, and since then has been documented throughout much of the Midwest.

What does tatters look like?

Trees with tatters have leaves that are lacy and shredded. Some leaves may appear as though the tissue between veins has been neatly ripped out, while other leaves have an irregular pattern of damage. The amount of damage may vary from leaf to leaf and branch to branch. Adjacent oak trees may show different amounts of damage due to genetic variability, variation in environmental conditions, or other external factors. Tatters is commonly confused with herbicide damage (see UW Plant Disease Facts D0060, Herbicide Damage), or damage by leaf-feeding insects.

Where does tatters come from?

The cause of tatters has not been precisely determined. Tatters is thought to be a physiological disorder caused by damage to leaf tissue (e.g., cold injury) in the bud-stage or during the opening of buds in the spring.

How do I save a tree with tatters?

DO NOT panic. Trees affected with tatters often produce replacement leaves within two to three weeks after tattered leaves appear. However, producing new leaves weakens trees and may make them more susceptible to other diseases and drought stress. If your trees suffer from tatters, make sure they receive sufficient water (approximately one inch per week for established trees). If rainfall is insufficient, use a drip hose or soaker hose to apply supplemental water around the drip line of the tree (i.e., the edge of where the branches extend). To prevent competition for water and nutrients, remove grass within the drip line of your trees and replace it with shredded hardwood, pine or cedar mulch. On heavy, clay soils, use one to two inches of mulch. On lighter, sandy soils, use three to four inches of mulch. Be sure to keep mulch four inches from the tree trunks. Fertilize trees only based on a soil nutrient test.

How do I avoid problems with tatters in the future?

There is no known method for preventing tatters. However, the occurrence of tatters one year does not guarantee that the same trees will suffer from tatters in subsequent years.

For more information on tatters:

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

* Completed as partial fulfillment of the requirements for Plant Pathology 699 – Plant Pathology Special Topics at the University of Wisconsin-Madison.

Thanks to Diana Alfuth, Phil Pellitteri 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.qa.webhosting.cals.wisc.edu.

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

Disease - Needled Woody Ornamental

Swiss Needle Cast

August 18, 2015 hudelson

UW Plant Disease Facts

Authors: Ann Joy and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/02/2024

D-number: D0109

What is Swiss needle cast?

Swiss needle cast is a fungal disease of Douglas-fir. This tree is native to the Rocky Mountains and the Pacific Coast but has been grown in Wisconsin as a landscape ornamental and as a Christmas tree. Swiss needle cast can limit the aesthetic appeal of Douglas-fir grown in landscape settings, as well as the marketability of Douglas-fir grown in Christmas tree production.

Fruiting bodies of the Swiss needle cast fungus on the undersides of needles.

What does Swiss needle cast look like?

Infected needles become discolored (blotchy yellow-green or completely yellow) and then brown from the tips. Older needles are more severely affected than younger needles. Brown needles drop prematurely, leaving twigs with only the newest growth. Using a hand lens, small, black reproductive structures of the Swiss needle cast fungus can be seen in two diffuse bands on the undersurface of infected needles.

Where does Swiss needle cast come from?

Swiss needle cast is caused by the fungus Nothophaeocryptopus gaeumannii. Spore production, needle infection, and symptom development are favored by wet environmental conditions (e.g., rainy weather). Infections primarily occur on new needles as they emerge and expand in the spring. Fully expanded needles are less susceptible to infection. Once infection has occurred, fruiting bodies (i.e., reproductive structures) form and produce spores on both discolored and green needles. Spores may be produced for several seasons before needles drop.

How can I save a tree with Swiss needle cast?

Infected needles cannot be cured. However, fungicide sprays containing chlorothalonil or mancozeb may help prevent additional infections on small trees where complete, uniform coverage is possible. Fungicide treatments are not recommended for large trees. For plantation and landscape trees, apply two fungicide applications, the first when buds are ½ to two inches long, and the second about three weeks later. In the more stressful environment of nurseries, trees may require sprays every two weeks through mid-August. Using preventive treatments, infected trees may regain their lush, full look within two years. Be sure to read and follow all label instructions of the fungicide that you select to ensure that you use the product in the safest and most effective manner possible.

How can I prevent Swiss needle cast in the future?

Use Douglas-firs grown from seed originating in Pacific Coast areas rather than those grown from seed originating in the Rocky Mountains. Pacific Coast trees appear to be less susceptible to Swiss needle cast. Also, use resistant and tolerant varieties where available. Purchase stock from a reputable nursery; Nothophaeocryptopus gaeumannii is often spread through infected nursery stock. When planting Douglas-firs, choose a site that has well-drained, but moist soil with a neutral to slightly acidic pH and allow adequate spacing between trees to promote increased airflow and quicker drying of needles. This drier environment is less favorable for infection and disease development. Make sure trees have sufficient water and are fertilized properly (based on soil and needle nutrient tests) to reduce stress that may increase trees’ susceptibility to Swiss needle cast.

For more information on Swiss needle cast:

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, Thad Kohlenberg, and Judy Reith-Rozelle 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.qa.webhosting.cals.wisc.edu.

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


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