Category Archives: Disease – Broad Leafed Woody Ornamental

Bacterial Wetwood

July 6, 2015 hudelson

UW Plant Disease Facts

Authors: Mary Francis Heimann*, O.S.F. and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0013

What is bacterial wetwood?

Bacterial wetwood, also known as “slime flux”, is a visually frightening-looking, but typically non-lethal, disorder of many types of deciduous trees. This disorder can reduce the aesthetic appeal of landscape trees, and more seriously, can substantially reduce the value of forest trees used for lumber. Bacterial wetwood most commonly affects elm and poplar, but can also be a serious problem on aspen, maple, and mulberry.

Bacterial wetwood leads to discolored, rancid-smelling areas on tree trunks.

What does bacterial wetwood look like?

Trees suffering from bacterial wetwood have areas where liquid oozes from their trunks. This ooze may flow freely at certain times of the growing season, but then may stop flowing at others. The ooze leads to streaked, discolored, water-soaked areas on tree trunks. The ooze is often colonized by bacteria, as well as yeasts and other fungi. These organisms can give the ooze a slimy, sometimes brightly-colored (i.e., pink or orange) appearance as well as a highly disagreeable, rancid smell. Internally, bacterial wetwood can be associated with localized areas of wood decay.

Where does bacterial wetwood come from?

Bacterial wetwood arises when localized wet areas develop in the heartwood or sapwood of tree trunks. These areas are colonized by a diverse assortment of bacteria (e.g., Enterobacterium, Klebsiella, Pseudomonas and many others) that can enter trees through root, branch or trunk wounds. As these bacteria feed and grow, often under anaerobic conditions (i.e., conditions without oxygen), they can produce gases such as methane, carbon dioxide, or nitrogen gas. These gases build up pressure, causing movement of interior liquids to the exterior of the trunk where they escape through wounds and cracks.

How do I save a tree with bacterial wetwood?

Bacterial wetwood is a chronic disorder and affected trees cannot be cured. To limit the unsightly staining of bark caused by bacterial wetwood, try to identify where the ooze is exiting from the trunk and insert a long, plastic tube at this location to direct the ooze away from the trunk and to the ground at the base of the tree. There has been speculation that the build-up of gases due to bacterial wetwood might cause a tree to explode. However, there have been no reliable reports of this ever happening.

How do I avoid problems with bacterial wetwood in the future?

There is little you can do to prevent problems with bacterial wetwood. Many affected trees were likely invaded by wetwood-associated bacteria in the seedling stage. Developing a healthy tolerance for bacterial wetwood, when it occurs, is perhaps the best method for coping with this disorder.

For more information on bacterial wetwood:

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

*Mary Francis Heimann is a Distinguished Outreach Specialist Emerita at the University of Wisconsin-Madison.

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 Mike Maddox, Patti Nagai 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 - Broad Leafed Woody Ornamental, Disease - Fruit Crop

Bacterial Canker

July 6, 2015 hudelson

UW Plant Disease Facts

Authors: Mary Francis Heimann* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0009

What is bacterial canker?

Bacterial canker is a common and sometimes lethal disease of trees in the genus Prunus including cherry, plum and peach. Bacterial canker is sometimes also referred to as “gummosis”, “blossom blast”, “dieback”, “spur blight” and “twig blight”.

Ooze (see arrow) on Prunus branches or trunks can indicate a bacterial canker problem.

What does bacterial canker look like?

Often branch dieback is the first symptom of bacterial canker that homeowners notice. However, other more subtle symptoms of flowers, leaves, fruits and branches typically precede this dieback. Initially, infected trees are symptomless. Infected flowers often open but then collapse. Infected leaves become spotted and yellowed. The centers of leaf spots often shothole (i.e., fall out). If spotting is severe, leaves may fall off. Infected fruits develop dead spots surrounded by water-soaked tissue. Spots can eventually develop into a fruit rot. Branch or trunk infections often occur at pruning sites and lead to cankers (i.e., sunken, dead areas). Cankers often produce a gummy, resinous ooze. Wood in the cankered area is typically discolored. Flower, fruit and branch infections can become systemic, leading to twig dieback, death of larger branches, or even death of an entire tree.

Where does bacterial canker come from?

Bacterial canker is caused by the bacteria Pseudomonas syringae pv. syringae (Pss) and P. syringae pv. mors-prunorum (Psm). These bacteria overwinter in cankers, in asymptomatic, systemically infected branches, and in buds of susceptible trees. Pss is also known to occur naturally on the leaves of many plants including many weed species. Both Pss and Psm can subsequently be spread by rain splash, wind, or insects. The bacteria can also be spread to healthy branches when contaminated pruning tools are used. Infections most often occur during cool, wet conditions.

How do I save a plant with bacterial canker?

Prune infected branches at least 12 inches below cankers or other dead tissue, and dispose of branches by burning (where allowed by local ordinance) or burying them. Prune branches only during the winter (e.g., Jan. and Feb.) or during dry periods in late summer (e.g., Aug.). DO NOT prune during the cool, wet periods (e.g., spring and fall). Disinfest pruning tools after each cut by treating them for at least 30 seconds with a 10% bleach solution or preferably 70% alcohol (e.g., rubbing alcohol straight from the bottle or a spray disinfectant). If you decide to use bleach, be sure to thoroughly rinse and oil your tools after pruning is complete to prevent rusting.

How do I avoid problems with bacterial canker in the future?

Healthy trees are better able to slow the development of bacterial canker. Therefore make sure that trees are watered and fertilized properly. Keep weeds and other plants that may harbor bacterial canker pathogens from around the base of susceptible trees. Copper-containing sprays have been advocated for bacterial canker management. However, in many areas, copper-resistant strains of Pss and Psm are present and therefore copper sprays are ineffective.

For more information on bacterial canker:

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

*Mary Francis Heimann is a Distinguished Outreach Specialist Emerita at the University of Wisconsin-Madison.

Thanks to Diana Alfuth, Patty McManus 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 - Broad Leafed Woody Ornamental

Bacterial Blight

July 6, 2015 hudelson

UW Plant Disease Facts

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

Last Revised: 02/28/2024

D-number: D0008

Death of lilac branch tips and leaves due to bacterial blight.

What is bacterial blight?

Bacterial blight, also known as blossom blight or shoot blight, is a common and often serious disease of Chinese, Japanese, Persian and common lilac, as well as walnut, apple, pear, plum and cherry. White flowering varieties of common lilac are most susceptible to the disease.

What does bacterial blight look like?

Initial symptoms of bacterial blight may include dark brown necrotic (dead) leaf spots with yellow halos. If leaf spots develop before leaves are fully expanded, leaf curling and twisting may result. More advanced symptoms include necrotic blotches starting at the leaf margins and advancing inward, as well as black streaking on twigs. In its most severe form, bacterial blight can result in the death of branch tips, leaves and blossoms.

Where does bacterial blight come from?

Bacterial blight is caused by the bacterium Pseudomonas syringae pv. syringae (Pss), which survives in diseased stem tissue (cankers), plant debris, and soil. Pss can be spread by insects and on pruning tools but is more commonly spread by wind and rain. Often Pss is found on the surface of healthy plants and does not cause disease. Infections can occur when the bacterium enters tissue through natural openings or through wounds caused by insects, pruning, wind damage or hail.

How do I save a plant with bacterial blight?

Prune diseased twigs 10 to 12 inches below the point of visible symptoms, and dispose of the branches by burning (where allowed by local ordinance) or burying them. Always prune in dry weather, and disinfest pruning tools after each cut by treating them for at least 30 seconds with a 10% bleach solution or preferably 70% alcohol (e.g., rubbing alcohol straight from the bottle or a spray disinfectant). If you decide to use bleach, be sure to thoroughly rinse and oil your tools after pruning is complete to prevent rusting.

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

When planting lilacs, provide adequate spacing between shrubs. Thin individual shrubs each winter to promote good air circulation (see University of Wisconsin Garden Facts XHT1015, Pruning Deciduous Shrubs, for pruning tips). Properly water, fertilize and mulch shrubs to avoid stress that may predispose them to disease. Avoid overhead watering that may keep leaves wet. If you have had chronic problems with bacterial blight, you may want to use a combination of copper and mancozeb-containing fungicides for control. Apply fungicides two to three times at seven to 10 day intervals as leaves emerge, but before symptoms develop. Read and follow all label instructions of the fungicide that you select to ensure that you use the fungicide in the safest and most effective manner possible.

For more information on bacterial 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

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

Thanks to Ann Joy, Kristin Kleeberger and Mike Maddox 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

Ash Yellows

July 6, 2015 hudelson

UW Plant Disease Facts

Authors: Jim Olis* and Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0006

What is ash yellows?

Ash yellows is a chronic, systemic disease that affects ash trees of all ages. White ash is particularly susceptible to ash yellows. Ash yellows likely occurs wherever ash is grown and has been reported widely in the United States and southern Canada. The organism that causes ash yellows also causes a disease called lilac witches’-broom.

Brooming symptoms in an ash tree caused by ash yellows.

What does ash yellows look like?

Symptoms of ash yellows usually occur within three years of infection. Infected trees typically grow at a much slower rate than non-infected trees, although this may be difficult to detect in an isolated, single tree. The rate of growth of an infected tree may be as little as one half that of a healthy tree. Leaves on infected trees are frequently smaller, thinner and lighter green than normal. Often, but not always, affected trees will produce branches in tufts, a symptom that is called “brooming”. Eventually, branches in the crown will die and this dieback can continue until the entire crown is dead.

Where does ash yellows come from?

Ash yellows is caused by the phytoplasma, Candidatus Phytoplasma fraxini. Phytoplasmas are bacteria-like organisms that live and survive in the phloem (the food-conducting tissue) of infected plants. Leafhoppers are thought to be the primary means by which this pathogen is moved from tree to tree.

How do I save a tree with ash yellows?

There is no known cure for ash yellows, but some infected trees may live and grow slowly with the disease for many years. Ash trees suspected of having ash yellows should be tested for the disease, and those trees that test positive should be removed immediately to prevent spread of the ash yellows phytoplasma to other trees in the area. Wood harvested from infected trees does not serve as a source of the phytoplasma and can be used for woodworking or firewood, or chipped for mulch.

How do I avoid problems with ash yellows in the future?

Avoid growing ash trees in areas where ash yellows is prevalent. When choosing a lilac, select a variety of common lilac as these varieties appear to have tolerance to the ash yellows phytoplasma. Avoid using S. josikaea, S. reticulata and S. sweginzowii (or hybrids of these species with either S. komarowii or S. villosa), as these lilacs appear to be highly susceptible. It is unclear if the use of insecticides (or other means) to control leafhoppers can help control the spread of this pathogen.

For more information on ash yellows and ash yellows testing:

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 BS in Plant Pathology at the University of Wisconsin Madison.

Thanks to Lis Friemoth, Ann Joy and Patti Nagai 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 - Fruit Crop, Disease - Needled Woody Ornamental

Armillaria Root Disease

July 6, 2015 hudelson

UW Plant Disease Facts

Authors: Michael Amman, UW-Madison Forest Ecology and Management and Glen R. Stanosz, Ph. D., UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0005

What is Armillaria root disease?

Armillaria root disease, also known as shoestring root rot, is an often lethal disease of tree and shrubs. It can affect almost any conifer or hardwood species, from seedling to maturity. Herbaceous plants can also be affected. Trees and shrubs stressed due to drought or defoliation can be particularly susceptible to Armillaria root disease.

White mats of fungal tissue called mycelial fans (arrow) may be present within and beneath the bark of stems and roots affected by Armillaria root disease.

Where does Armillaria root disease come from?

Armillaria root disease results from colonization of trees and shrubs by fungi in the genus Armillaria. These fungi produce tough, cord-like strands called “rhizomorphs” that grow from decaying stumps and roots through the soil. Infection of other trees or shrubs can result from penetration of intact roots by rhizomorphs. In late summer or early fall, honey-colored mushrooms of Armillaria fungi develop near the bases of colonized plants and produce spores that are distributed by wind. Infection also can occur after these spores germinate in wounds on stems or roots.

What does Armillaria root disease look like?

Above-ground symptoms of Armillaria root disease may include slow growth, yellowing and dwarfing of foliage, and thin crowns. Dieback of twigs and branches also may occur as the disease progresses. These symptoms may develop slowly and intensify over many years. However, trees and shrubs also may be rapidly killed, with leaves or needles suddenly wilting or browning on a plant that appeared healthy just days or weeks earlier. Bark on lower stems or roots may be killed and crack, with flow of resin common on conifers. Thin white mats of fungal tissue called “mycelial fans” may be present within and beneath killed bark. Stem and root tissue decayed by Armillaria fungi is often water-soaked, creamy to yellow in color, and spongy or stringy in texture. Rhizomorphs are commonly seen on or beneath the bark and growing from decayed stumps and roots.

How do I save a tree affected by Armillaria root disease?

There is no practical way to eliminate Armillaria from trees that are already colonized by the fungus. The useful life of an affected tree might be prolonged however, by supplemental watering during dry periods and appropriate fertilization to improve overall host condition. In very vigorous trees, the Armillaria fungi may be “walled off” and confined to just a portion of the root system or root collar. There are no chemical treatments that can effectively target Armillaria fungi within diseased trees.

How do I avoid Armillaria root disease in the future?

Practices that maintain trees in vigorous condition are the best means of preventing Armillaria root disease. Watering and fertilization to avoid stress will help trees resist infection. Because Armillaria root disease often develops in response to defoliation, suppression of both insect and leaf pathogen defoliators will indirectly reduce the occurrence and severity of Armillaria root disease. Because stumps and root systems of previously colonized trees can serve as “food bases” supporting rhizomorph growth for many years, thorough removal of stumps and root systems will reduce the risk of infection of other trees.

For more information on Armillaria root 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

Thanks to Ann Joy and 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

Anthracnose

June 30, 2015 hudelson

UW Plant Disease Facts

Anthracnose is very common on many types of trees and shrubs. It often occurs on the leaves of ash (left) and maple (right) trees, causing blotchy-brown, dead areas.

Authors: Brian Hudelson, UW-Madison Plant Pathology

Last Revised: 02/28/2024

D-number: D0002

What is anthracnose?

Anthracnose is the name of several common fungal diseases that affect the foliage of woody ornamentals in Wisconsin. Trees that are most commonly and severely affected by anthracnose include ash, maple, white oak, sycamore, and walnut. Anthracnose typically affects young leaf tissue.

What does anthracnose look like?

Symptoms of anthracnose vary from host to host, but in general include irregular spots, and dead areas on leaves that often follow the veins of the leaves. Affected tissue can vary in color but is often tan or brown. Severely affected leaves often curl and may fall off. In some tree species, such as sycamore, twigs can also become infected leading to twig dieback.

Where does anthracnose come from?

Anthracnose is caused by several fungi (many historically classified in the genus Gloeosporium) that survive in leaf litter. These fungi are host specific. The anthracnose fungus that infects one type of tree (e.g., ash) is not the same one that infects another type of tree (e.g., maple). However, when anthracnose occurs on one tree, then weather conditions (typically cool and moist conditions) are favorable for development of the disease on many types of trees.

Anthracnose can be severe on some hosts. On white oak (left), it can cause extensive leaf browning and curling. On sycamore (right), anthracnose can cause twig dieback.

How do I save a tree with anthracnose?

DO NOT panic. For many trees, anthracnose is a cosmetic disease. It may make a tree look a little ragged but will not kill the tree. However, if a tree has been defoliated by anthracnose for several years, or it is a tree, such as a sycamore, where twig infections can occur, then you may want to use a fungicide for disease control. Three treatments are typically needed for adequate control: one at bud break, one when leaves are half expanded, and one when leaves are fully expanded. Fungicides containing copper, chlorothalonil, or mancozeb are registered for anthracnose control in Wisconsin. DO NOT use the same active ingredient for all treatments. Instead, alternate the use of at least two active ingredients to help minimize problems with fungicide-resistant strains of anthracnose fungi. Be sure to read and follow all label instructions of the fungicide(s) that you select to ensure that you use the fungicide(s) in the safest and most effective manner possible.

How do I avoid problems with anthracnose in the future?

You can reduce the number of spores that cause anthracnose infections by removing and disposing of fallen, infected leaves in the autumn. Leaves can be burned (where allowed), buried or composted. When composting, make sure that your compost pile reaches high temperature (approximately 140°F). Also, make sure that your compost pile is routinely turned so that leaves on the outside of the pile eventually end up in the center of the pile. The combination of high temperature and decay of leaf tissue in a compost pile helps eliminate anthracnose fungi. Also, maintain good tree vigor by watering and fertilizing trees appropriately. Check with your local county Extension agent for details on how to properly care for trees.

For more information on anthracnose:

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 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.qa.webhosting.cals.wisc.edu.

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