Category Archives: Disease – Broad Leafed Woody Ornamental

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Herbaceous Ornamental, Disease - Needled Woody Ornamental, Disease - Vegetable, Misc

Wood Mulch and Tree Health

August 20, 2015 hudelson

UW Plant Disease Facts

Authors: Jane Cummings-Carlson and John Kyhl, Wisconsin Department of Natural Resources Gina Foreman and Brian Hudelson, UW-Madison Plant Pathology
Last Revised: 03/02/2024
D-Number: D0128

What are the benefits of wood mulch?

Wood mulch is typically available as chipped wood, or shredded or chunked bark, and can contribute to tree health in many ways. When high quality, composted mulches are applied two to four inches deep in a ring three to six feet in diameter (or greater) from the trunk of a tree, mulch can help preserve moisture, control weeds, limit damage to the trunk from mowers and string trimmers and moderate the soil temperature. Use four inches of mulch when soils are light and well-drained, and two inches of mulch on heavier, clay soils.

Use of properly composted mulches can be beneficial to trees and shrubs in the landscape.

Can wood mulch harm trees?

Use of improperly composted mulches (some-times called “sour mulches”), can lead to tree nutrient deficiencies. Sour mulches can also produce gases like methane and ammonia that can be toxic to plants. Foliage on trees surrounded by sour mulches may initially turn yellow, then brown, die and fall off. If your mulch smells like vinegar, ammonia or sulfur, it is likely a sour mulch and should be removed. Replace the sour mulch with a high quality, composted mulch and consult with your local Extension agent about testing the soil for nutrient deficiencies. Fertilize appropriately based on the results of these tests.

Improper application of mulch can also lead to problems. Piling wood mulch up against the trunk of a tree can keep the bark underneath excessively wet. This wetness can contribute to bark decay. In addition, use of thick mulch layers (greater than four inches) can lead to overly wet soils that are favorable for development of root rots (see UW Plant Disease Facts D0094, Root and Crown Rot). To avoid these problems, make sure mulch is applied at least four inches away from the trunk of a tree and that the mulch layer is the appropriate thickness for the soil type in your landscape (see above).

Does woody mulch harbor or attract insects?

Insects such as earwigs [see UW Bulletin A3640, Controlling Earwigs (available at https://learningstore.extension.wisc.edu/)], centipedes (see University of Wisconsin Garden Facts XHT1113, Centipedes), millipedes (see University of Wisconsin Garden Facts XHT1108, Millipedes) and sowbugs (see University of Wisconsin Garden Facts XHT1110, Sowbugs) can feed on decaying organic matter in mulches. While these insects are often only nuisances, earwigs can feed on and cause damage to a variety of ornamentals, particularly to flowering plants. If mulch is used near entrances to a home or around basement windows, these unwanted insects may get inside. Termites ingest wood and can be attracted to wood mulch, but new termite colonies are not likely to become established due to use of wood mulches. Typically, termites are not a problem in Wisconsin, and when colonies are found, they occur only in the southern half of the state.

Carpenter ants [see UW Bulletin A3641, Controlling Carpenter Ants (available at https://learningstore.extension.wisc.edu/)] and powderpost beetles (see University of Wisconsin Garden Facts XHT1053, Powderpost Beetles) are unlikely to utilize mulch as a food source because conditions required for their development would not be satisfied by wood mulch. Carpenter ants do not ingest wood as a food source; instead, they chew non-living wood (in trees or landscape timbers, etc.) to excavate galleries in which they live and raise their young. Since wood mulch is composed of small wooden pieces, it would not serve as a home. To avoid potential insect problems, keep mulch as far away from the foundation of your home as possible and seal all holes and crevices that insects might use as entry points. Also, periodically inspect landscape timbers and the house for termites.

Does woody mulch harbor tree pathogens?

Wood mulch may come from many sources, including trees and shrubs that have died from a wide range of diseases. To be harmful to your trees, disease-causing organisms (pathogens) would have to survive in mulch and these organisms would have to move from the mulch either directly, or through the soil, to their new host – your tree. There is currently very little research on this topic.

Elm trees killed by Dutch elm disease (see UW Plant Disease Facts D0045, Dutch Elm Disease), can serve as breeding areas for native and European elm bark beetles. Bark beetles that breed in logs or firewood from these trees can pick up the fungi that cause Dutch elm disease (Ophiostoma ulmi and Ophiostoma novo-ulmi) and carry these fungi from tree to tree. Chipping infected elm trees creates an unfavorable environment for bark beetles yet there is no scientific literature that describes the level of risk of transmitting the Dutch elm disease fungi from wood chips or bark chunks to healthy elms.

Oak trees killed by oak wilt (see UW Plant Disease Facts D0075, Oak Wilt) can be attractive to several sap-feeding beetles that can potentially pick up the oak wilt fungus (Bretziella fagacearum) and move it in the landscape. This process is affected by moisture and temperature and would likely be disrupted by the chipping and composting process yet there is no scientific literature that describes the level of risk of transmitting the oak wilt disease fungus from wood chips or bark chunks to healthy oaks.

Research at the University of Wisconsin-Madison suggests that wood chip mulches produced from trees suffering from Verticillium wilt (see UW Plant Disease Facts D0121, Verticillium Wilt of Trees and Shrubs) can serve as a source of the fungus (Verticillium dahliae) that causes the disease. These studies show that Verticillium can survive for at least one year in mulch and that use of this contaminated mulch can lead to Verticillium wilt in both woody and herbaceous plants. Therefore use of mulches produced from trees with Verticillium wilt should be avoided.

For more information on wood mulch and tree health:

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).

Thanks to Ann Joy, Laura Jull 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.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 - Needled Woody Ornamental

Winter Burn

August 19, 2015 hudelson

UW Plant Disease Facts

Authors: Laura Jull, UW-Madison Horticulture

Last Revised: 03/02/2024

D-number: D0127

What is winter burn?

Winter burn is a common problem of evergreens including those with broad leaves (e.g., boxwood, holly, rhododendron), needles (e.g., fir, hemlock, pine, spruce, yew) and scale-like leaves (e.g., arborvitae, false cypress, juniper) grown in open, unprotected locations and exposed to severe winter conditions. Evergreen plants that are marginally hardy in a location (i.e., not well-adapted to local winter conditions) are at increased risk for winter burn. Winter burn can be so severe that affected plants may die and/or require replacement.

Browning due to winter burn on dwarf Alberta spruce.

What does winter burn look like?

Winter burn symptoms often become apparent as the snow melts and spring temperatures rise. Foliage starts to brown at the tips of branches with browning progressing inward toward the center of the plant. On broad-leaved evergreens, leaf edges typically brown first, followed by browning of entire leaves. Foliage facing south, southwest or west is most often affected. Symptomatic foliage often begins to drop off starting in spring and continuing through mid-summer as new foliage is produced. In extreme cases, entire plants can brown and die.

What causes winter burn?

There are many factors that can contribute to winter burn. In general, plants with shallow or poorly-developed root systems that do not efficiently take up water (e.g., recent transplants) are more prone to winter burn. Warm fall temperatures that delay the onset of plant dormancy can also contribute to winter burn. Under such conditions, plants are not prepared for the subsequent rapid onset of freezing winter temperatures, and as a result damage to foliage occurs. Similar cold injury can occur mid-winter when temperatures drop sharply at sunset causing foliage that has warmed during the day to rapidly cool and freeze. In addition, on sunny winter days, foliage (particularly foliage facing the sun) can begin to transpire (i.e., naturally lose water through the foliage). Because the ground is frozen, plant roots cannot take up water and replace the water that has been lost from the foliage. As a result, foliage dries and browns. Foliage under snow or facing away from the sun and direct winds is usually not damaged. Strong winter winds can lead to additional water loss making winter burn more severe. Colder than normal winter temperatures and longer than normal winters can also be factors in the development of winter burn, especially if below normal temperatures occur into April (the time of year when plants normally come out of dormancy and are most susceptible to winter injury). Finally, exposure of plants to salt used to de-ice roads, driveways and sideways during the winter can make plants more prone to winter burn injury.

How do I save a plant with winter burn?

For evergreens such as arborvitaes, boxwoods, junipers and yews, prune out dead, brown, damaged or dying tissue in mid-spring after new foliage is produced. If new foliage has not yet emerged by spring, scratch the bark on affected branches and look for green tissue underneath. Also gently peel back the bud scales to look for inner green bud tissue. If the stem or bud tissue is green, buds on the branch may still break to form new foliage. If the tissue is brown, the branch is most likely dead and you should prune the branch back to a live, lateral bud or branch. Such buds and branches may be far back inside the canopy and pruning may remove a substantial amount of the plant. Pines, spruces and firs typically produce new growth at branch tips in spring that will replace winter burn-damaged needles, and thus pruning may not be required on these evergreens. After a couple of growing seasons, new foliage will fill in the areas that were damaged. If an entire evergreen is brown, recovery is unlikely and the plant should be replaced with something (e.g., a deciduous shrub or tree) that is better-suited to the site.

How do I avoid problems with winter burn in the future?

Use a variety of strategies to prevent winter burn before winter arrives.

Plant the right plant in the right place.

Buy plants that are rated as cold hardy for your location and are well-adapted to local growing and soil conditions. Plants exposed to drying winter sun and winds are more likely to be injured. Therefore, avoid planting winter injury sensitive evergreens, particularly those that require shade or that are marginally cold-hardy, in exposed, sunny, windy areas. Plant them on the northeast or east side of a building or in a protected courtyard. Plant boxwoods, hemlocks, rhododendrons, and yews in partial shade to provide them added protection from winter sun and wind.

Plant evergreens at the right time of year.

Optimally, plant evergreens either in early spring (before buds break) or in late summer (i.e., August through September). Evergreens can be planted in the summer if you provide supplemental water. Avoid planting after early October in northern Wisconsin and after mid-October in southern Wisconsin as this will not allow sufficient time for roots to grow adequately before the ground freezes.

DO NOT prune evergreens in late summer or early fall.

Late season pruning of some non-native evergreens may encourage a flush of new growth that will not harden off properly before winter. See University of Wisconsin Garden Facts XHT1013, Pruning Evergreens, for details on when and how to prune specific evergreen trees and shrubs.

Mulch evergreens properly.

Apply two inches (on clay soils) to four inches (on sandy soils) of loose mulch (e.g., shredded hardwood, pine, or cedar bark; leaf compost; or wood chips) around the base of evergreens out to at least the drip line (e.g., the edge of where the branches extend). Keep mulch at least four inches away from the trunks of trees and the bases of shrubs. Proper mulch insulates roots from severe fluctuations of soil temperatures and reduces water loss. It also helps protect roots from injury due to heaving that occurs when soils go through cycles of freezing and thawing during the winter. Heaving can especially be a problem for shallow-rooted and newly planted evergreens. DO NOT mulch excessively or too close to plants as this can lead to damage by providing shelter for mice and voles (which can girdle trunks and branches) and by providing a favorable environment for disease development as well as insect activity and feeding.

Water plants properly.

Plants that are well-hydrated are less prone to winter burn. In particular, newly planted or young evergreens, especially those planted in open, exposed sites, those planted under eaves, or those planted in dry falls may suffer severe moisture loss during the winter and consequently severe winter burn. Established evergreens should receive approximately one inch of water per week and newly transplanted evergreens up to two inches of water per week during the growing season up until the soil freezes in the autumn or there is a significant snowfall. If supplemental watering is needed, use a soaker or drip hose to apply water near the drip lines of plants rather than using a sprinkler.

Avoid late summer or fall fertilization.

Applying quick-release, high-nitrogen fertilizers in late summer or fall could potentially stimulate growth of new foliage (particularly on some non-native evergreens) as well as inhibit proper onset of dormancy which can lead to damage over the winter. If you are concerned that your evergreens may need to be fertilized, submit a soil sample from around your plants to a professional soil testing lab that can provide specific information on what fertilizer to use and when to fertilize.

Protect plants during the winter.

Use burlap, canvas, snow fencing or other protective materials to create barriers that will protect plants from winter winds and sun. Install four to five foot tall stakes approximately two feet from the drip lines of plants especially on the south and west sides (or any side exposed to wind) and wrap protective materials around the stakes to create “fenced” barriers. Leave the top open. These barriers will deflect the wind and protect plants from direct exposure to the sun. Remove the barrier material promptly in spring. DO NOT tightly wrap individual plants with burlap as this can collect ice, trap moisture and make plants more susceptible to infection by disease-causing organisms. Use of anti-transpirant products to prevent water loss from foliage over the winter has been shown to have limited benefit. These materials degrade rapidly, require reapplication after each significant rain or snow event, and may not be effective in preventing water loss that can lead to winter burn.

For more information on winter burn:

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 Linda Chalker – Scott, Bert Cregg and Jean Ferdinandsen for reviewing this document.

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

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

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

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 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.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.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.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.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.wisc.edu.

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

Disease - Broad Leafed Woody Ornamental

Powdery Mildew – Deciduous Woody Ornamentals

August 15, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 03/01/2024

D-number: D0087

Many woody plants such as rose and lilac are susceptible to powdery mildew.

What is powdery mildew?

Powdery mildews are diseases that occur on the above-ground parts (especially the leaves) of many deciduous trees and shrubs, as well as herbaceous ornamental plants, indoor houseplants, and many agricultural crops. Conifers are not affected by these diseases.

What does powdery mildew look like?

The name of these diseases is descriptive. The upper and lower surfaces of leaves, as well as stems of infected plants, have a white, powdery appearance. They look as though someone has sprinkled them with talcum powder or powdered sugar.

Where does powdery mildew come from?

Powdery mildews are caused by many closely related fungi that survive in plant debris or on infected plants. These fungi are fairly host specific. The powdery mildew fungus that infects one type of plant (e.g., lilac) is not the same powdery mildew fungus that infects another (e.g., phlox). However, if you see powdery mildew on one plant, then weather conditions (high humidity) are favorable for development of the disease on a wide range of plants.

How do I save a plant with powdery mildew?

DO NOT panic! For many trees and shrubs (e.g., lilac), powdery mildews are cosmetic, non-lethal disease. For other plants (e.g., rose, ninebark) powdery mildews can cause severe leaf loss and even branch tip dieback.

Powdery mildew on ninebark can be so severe that it causes branch tip dieback.

When a highly valued plant has had severe leaf loss due to powdery mildew for several years, you may want to consider using a fungicide for control. Fungicides containing chlorothalonil, copper, mancozeb, myclobutanil, triadimefon, sulfur or thiophanate-methyl are registered for powdery mildew control. A combination of baking soda (1½ tablespoons) and a light weight (i.e., paraffin-based) horticultural oil (3 tablespoons) in water (1 gallon) has also been shown to be effective. Most products should be applied every seven to 14 days from bud break until humid weather subsides. DO NOT use myclobutanil, triadimefon, or thiophanate-methyl as the sole active ingredient for all treatments. If you decide to use one of these active ingredients, alternate its use with at least one of the other listed active ingredients to help minimize problems with fungicide-resistant strains of powdery mildew fungi. DO NOT alternate myclobutanil and triadimefon as these active ingredients are chemically related. Be sure to read and follow all label instructions of the fungicide(s) that you select to ensure that you use the product(s) in the safest and most effective manner possible. Also consider pretesting any product that you decide to use on a small number of leaves before treating an entire tree or shrub to make sure there are no toxic effects, particularly when treating during warmer weather.

How do I avoid problems with powdery mildew in the future?

Consider buying plant varieties that are powdery mildew resistant. This will not guarantee that your plants will be powdery mildew free every year, but should result in less severe disease when it occurs. Reduce the humidity around your plants by spacing them further apart to increase air flow. In established trees and shrubs, thin canopies to increase air flow. Be sure not to over-water as this can lead to higher air humidity as well. Finally, at the end of the growing season, remove and destroy any infected plant debris as this can serve as a source of spores for the next growing season. You can burn (where allowed by local ordinance), bury or hot compost this material.

For more information on powdery mildew:

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 Bill Halfman, Laura Jull, Patti Nagai and Amy Sausen for reviewing this document.

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

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

Disease - Broad Leafed Woody Ornamental

Rose Rust

August 15, 2015 hudelson

UW Plant Disease Facts

Authors: Robyn Roberts*, UW-Madison Plant Pathology

Last Revised: 03/01/2024

D-number: D0098

What is rose rust?

Rose rust is a common fungal disease found in much of North America (including the continental United States) and Europe. Rose rust affects many varieties of rose, though some varieties (e.g., hybrids) are more prone to the disease. Rose rust has been a perennial problem along the Pacific Coast of the United States where mild temperatures and high moisture are favorable for rust development. In the Midwest, extremes in winter and summer temperatures have historically tended to be less favorable for the disease. However, recent climate changes in Wisconsin have led to rose rust becoming more commonplace in the state.

Yellow spots on upper leaf surfaces with corresponding powdery, orange to black spots on lower leaf surfaces are typical of rose rust.

What does rose rust look like?

Rose rust often first appears on lower leaves, but eventually an entire plant can be affected. Typical symptoms include general yellowing of leaves followed by eventual leaf death. Affected rose stems (i.e., canes) can become curled and distorted. As the disease progresses, powdery orange or black, circular spots (called pustules) containing spores of the fungus that causes the disease form on the undersides of leaves. Corresponding yellow spots are visible on upper leaf surfaces above the pustules. Pustules may also form on stems and green flower parts (sepals). Rose rust usually develops in the spring and fall (when favorable mild temperatures and wet conditions are more common), but the disease can affect roses during the summer months as well.

Where does rose rust come from?

Rose rust is caused by several species of fungi in the genus Phragmidium. These fungi specifically infect roses. Rose rust is often introduced into a garden on infected shrubs purchased from a nursery or other rose supplier. Once introduced into a garden, rose rust fungi can overwinter in rose leaf debris, as well as on infected rose canes. In the spring, spores produced in debris and on canes can blow to newly emerging rose foliage, leading to new infections.

How do I save a plant with rose rust?

Control of rose rust is difficult once symptoms develop. Prune out affected canes and remove leaves as symptoms develop to prevent the spread of rust fungi to other rose shrubs. Destroy these materials by burning (where allowed by local ordinances) or burying them. In the fall, remove and destroy any remaining dead leaves and other rose debris to eliminate places where rose rust fungi can overwinter. If you notice a rust problem very early (before there are many symptoms), fungicide treatments may be useful for managing the disease; however, most fungicides work best when applied before any symptoms appear. If you decide to use fungicides for rust control, select products that are labeled for use on roses and that contains the active ingredients chlorothalonil, mancozeb, myclobutanil, propiconazole, sulfur or triforine. Treat every seven to 10 days, and DO NOT use the same active ingredient for all treatments, particularly if you decide to use myclobutanil, propiconazole or triforine. Instead, alternate use of the two active ingredients listed above to help minimize potential problems with fungicide-resistant strains of rose rust fungi. DO NOT alternate myclobutanil, propiconazole or triforine, as these active ingredients are chemically related. Be sure to read and follow all label instructions of the fungicides that you select to ensure that you use these products in the safest and most effective manner possible.

How do I avoid problems with rose rust in the future?

Whenever possible, plant rose varieties that are less susceptible to rose rust (i.e., avoid hybrid varieties). Always inspect new rose shrubs for rose rust (and other diseases) prior to purchase. DO NOT bring diseased shrubs into your garden. Plant rose shrubs far enough apart so that their foliage does not overlap, and thin your roses on a regular basis. Proper planting and pruning promote good air circulation that will facilitate rapid drying of leaves and canes, thus making the environment less favorable for rust development. Avoid working with your roses when they are wet as you are more likely to spread rust spores under these conditions. Fertilize and water roses appropriately. Well-cared-for plants tend to be less susceptible to disease. When watering, apply water at the base of your shrubs (e.g., with a soaker or drip hose) rather than over the leaves (e.g., with a sprinkler). Watering with a sprinkler tends to spread rust spores and wets leaves and canes, thus providing a more favorable environment for rust infections to occur.

For more information on rose 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

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

Thanks to Erica Arcibal, Rosemarie Bugs, Lisa Johnson, Cyndy King, Janet Roberts, Jillian Roberts and Rose Roberts for reviewing this document.

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

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

Disease - Broad Leafed Woody Ornamental, Disease - Fruit Crop, Disease - Needled Woody Ornamental

Root and Crown Rots

August 15, 2015 hudelson

UW Plant Disease Facts

Authors: Brian Hudelson, UW-Madison Plant Pathology and Laura Jull, UW-Madison Horticulture

Last Revised: 03/01/2024

D-number: D0094

Discoloration of maple crown and roots typical of Phytophthora root/crown rot.

What is root/crown rot?

Root/crown rot is a general term that describes any disease of woody ornamentals where the pathogen (causal organism) attacks and leads to the deterioration of a plant’s root system and/or lower trunk or branches near the soil line. Root rots can be chronic diseases or, more commonly, are acute and can lead to the death of the plant.

What does root/crown rot look like?

Gardeners often become aware root/crown rot when they see above ground symptoms. Affected plants are often slow-growing or stunted and may show signs of wilting. Often the canopy of an affected tree or shrub is thin, with foliage that is yellow or red, suggesting a nutrient deficiency. Careful examination of the roots/crowns of these plants reveals tissue that is soft and brown.

Where does root/crown rot come from?

Several soil-borne water molds (i.e., fungi-like organisms) and true fungi can cause root/crown rots, including (most frequently) Phytophthora spp. and Pythium spp. (both water molds), and Rhizoctonia solani and Fusarium spp. (both true fungi). These organisms have wide host ranges, and prefer wet soil conditions. Water mold root rot organisms such as Pythium and Phytophtora produce thick-walled spores (called oospores) that can survive for long periods (years to decades) in soil.

How do I save a plant with root/crown rot?

REDUCE SOIL MOISTURE! Provide enough water to fulfill a plant’s growth needs and prevent drought stress, but DO NOT over-water. Remove excess mulch (greater than four inches) around trees and shrubs. Excessive mulch can lead to overly wet soils.

A thinning canopy with red or yellow leaves can indicate a root/crown rot problem.

Chemical fungicides (e.g., PCNB, mefenoxam, metalaxyl, etridiazole, thiophanate-methyl and propiconazole) and biological control agents (e.g., Gliocladium, Streptomyces, and Trichoderma) are labeled for root/crown rot control. However, DO NOT use these products unless you know exactly which root/crown rot pathogen(s) is(are) affecting your trees and shrubs. Contact your county Extension agent for details on obtaining an accurate root/crown rot diagnosis and for advice on which, if any, fungicides you should consider using.

How do I avoid problems with root/crown rots?

Buy plants from a reputable source, and make sure they are root/crown rot-free prior to purchase. Establish healthy plants in a well-drained site, and when planting, place the root collar just at the soil surface. To moderate soil moisture, add organic material (e.g., leaf litter or compost) to heavy soils to increase soil drainage, and DO NOT over-water. Also, DO NOT apply more than three inches of mulch around trees and shrubs, and keep mulch from directly contacting the base of trunks and stems. Prevent physical damage (e.g., lawnmower injury) that can provide entry points for root/crown rot pathogens. Finally, minimize movement of root/crown rot fungi in your garden. DO NOT move soil or plants from areas where plants are having root/crown rot problems. DO NOT water plants with water contaminated with soil (and thus potentially with root/crown rot organisms). After working with plants with root/crown rot, decontaminate tools and footwear by treating for at least 30 seconds with a 10% bleach solution or 70% alcohol (e.g., rubbing alcohol, certain spray disinfectants). If you use bleach to decontaminate metal tools, be sure to thoroughly rinse and oil your tools after you are done gardening to prevent rusting.

For more information on root/crown rots:

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 Karen Delahaut, Ann Joy and Sharon Morrisey for reviewing this document.

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

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