Tree bark fungus identification

Mulberry Tree Diseases

schwarze maulbeeren image by romy mitterlechner from

Mulberry, known botanically as the species Morus, are deciduous flowering and fruiting trees. There are two main cultivars, Morus rubra and Morus alba or red and white mulberry, respectively. They are grown for their large leafy shade canopy, for their decorative catkins and for their edible fruit that resemble blackberries when ripe. The fruit are also a desired food source for birds. While not considered particularly disease prone, mulberry trees be susceptible to a range of common ailments that affect broadleaf trees.

Sooty Canker

Sooty canker is a fungal disease known scientifically as Hendersonula toruloidea. It is one of the more common mulberry diseases and creates cankers or wounds in the tree trunk bark and branches and causes the foliage and woody tissues to wilt and then die back. It takes hold in winter but its effects are most pronounced in the summer when brown wet rotting spots appear on the branches, the leaves wilt, the bark splits and splotches of black soot-like mold become visible. When the mold builds up it will kill the surrounding wood disrupting the flow of water and nutrients in the tree and in extreme infestations kill the tree. It is opportunistic and seizes on stressed or weak trees or at pruning wound sites.

Armillaria Root Rot

Armillaria root rot, known scientifically as Armillaria mellea and more commonly as Oak root fungus or shoestring disease, can also infect mulberry trees. The infection is largely internal and underground, rotting out the roots and woody tissues. External evidence comes in the form of shrinking or puny looking foliage, yellowing or browning leaves and unusual or off-season leaf drop. The top branches or limbs will die back and the effects will progress down the canopy. Red to brown mushrooms or fungal blooms can crop up at the base of the trunk or along surface roots which is an indicator of the fungal activity.

Bacterial Blight

Bacterial blight, known scientifically as Pseudomonas syringae, can infect the leaves and woody tissue of fruiting mulberry trees. Spotting on the top surface or the leaves with black or brown irregularly shaped lesions, flowers, fruits and catkins and branches can shrivel or die back and the leaf veins can darken in color. Cankers can infect the wood and in severe problems the wood will weep from the canker wound when in moist environments. The prevalence of bacterial blight is spurred on by rain and will be more severe the wetter an area is for sustained periods without intervals of dry conditions.

Invasive Mulberry Tree – Gardening Advice


Q: My 15-year-old mulberry tree provides wonderful summer shade, but it’s growing up into the power lines, and my neighbor says its roots are damaging his underground sprinkler system. Can I prune the roots to keep them out of his yard? Should I replace the tree? – Sandra Todd, Los Gatos, Calif.

A: Garden diplomacy between neighbors is always delicate. And in this case, responsibility for solving the problem rests with both sides. Your mulberry’s roots didn’t cause the problem – at least, not at the very start. It’s physically impossible for roots to break into pipes or to drill through them to get at water, but they will follow leaking water to its source, and then squeeze through even the tiniest existing hole or fissure. Somewhere, somehow, your neighbor’s sprinkler system must have sprung a leak, luring mulberry roots next door for a drink. Don’t bother trying to cut back the roots or digging a trench for a concrete or plastic root barrier. Wherever the water is, those roots will find it, even diving under barriers as deep as 4 feet. First, the sprinkler pipes should be fixed – they are wasting water.

The sad news for you is that the mulberry tree probably ought to go. Many people plant mulberries because they grow quickly; they can also quickly grow too tall (30 to 50 feet in only 10 to 20 years). I’d replace your mulberry with a smaller tree, which will not spread its roots as far and won’t need a periodic buzz cut from the power lineman, either. Since the canopy of your replacement tree will cover less ground, plant it a little closer to the spot where you need summertime shade. Following are some appealing alternative trees. All drop their leaves in winter, like the ulberry. They will take many years to reach a height of 25 feet and can be maintained at that height or lower with moderate pruning.

For exotic bloom you can’t beat a chitalpa, a cross between the eastern catalpa and a desert cousin, chilopsis. This hybrid tree flowers over a long period in early summer, producing abundant orchidlike blossoms. Crab apples thrive in your region, and many varieties make a wonderful small but spreading tree to sit under. Ask a local nursery for a crab apple with fruit that persists into the winter. You probably think of crape myrtle as a large shrub, but it’s easy to train into a small, multistemmed tree. The best are modern varieties developed for disease-resistant foliage: ‘Sioux,’ ‘Comanche’, and others named for Native American tribes. Flowers range from purple through a wide range of reds to white. In the winter, crape myrtles display lovely peeling bark. Japanese persimmon trees are most glorious in the fall and early winter, when the leaves turn golden and the branches bear avocado-size fruit the color of pumpkins.

It won’t be long until the trees begin to come out of their dormancy and start to bud with leaves, blossoms, and new growth. However, coming out of this long winter’s nap leaves them (no pun intended) very susceptible to fungal infections, many of which start in the bark. These infections can spread to the entire body, and without proper care these trees can lose their leaves, fruit, and limbs as they slowly die.

Fungal diseases in the bark are fairly easy for trained arborists to deal with, but the sooner they are caught, the better! Here are the big five fungal diseases we cope with in Ontario and what you should do to prevent them from harming your tree.

Beech Bark Disease

Beech bark disease is a newer threat affecting beech trees (Fagus grandifolia), and it’s brought about by native nectria fungus pairing up with the invasive European beech scale insect. The insects feed on the beech sap by burrowing into the bark, and once inside, the nectria fungus on the beech scale colonize the bark and interior of the tree. The resulting infection produces cankers, oozing sores and blisters in the bark that can cover much of the trunk. It also weakens the tree, making it vulnerable to other stresses.

This disease has resulted in a lot of dieback throughout Eastern Canada and the United States but only recently has been identified in southern Ontario. If your tree is very valuable to you, chemical treatment is available and should be used before the insects and fungus spread to other trees. Interestingly, some beech trees are resistant to the infection, and if one tree is unaffected in a group of infected trees, it can be a great source of fungal-resistant seeds.

Dutch Elm Disease

Dutch elm disease is an invasive fungal infection that was first identified in Ontario in 1946. It can be spread by both the native elm bark beetle and the invasive European elm bark beetle. These beetles, covered in fungal spores, dig into the bark; while they munch away on the healthy tree sap, the fungus spreads into the tree’s sap-conducting tissues. Infections cause wilting and browning of the foliage and can kill a tree within one to three years.

If you have elm trees on your property, careful monitoring is your best prevention. Insecticides can be used in the spring and fall to kill the elm bark beetles, and a fungicide can be injected into your tree to rid its system of Dutch elm disease.

Butternut Canker

Affecting butternut trees and certain members of the walnut family, butternut cankers are caused by the fungus Ophiognomonia clavigignenti-juglandacearum (try saying that even one time fast). In some native US butternut populations, the death rate from this fungal infection can be up to 90%. This has lead to butternut trees being placed on Ontario’s Endangered Species list.

To combat this infection, start by identifying the butternut trees in your area and noting the formation of cankers on them. If they have leafless and dying branches, black fluid oozing out of cracks in the bark (or a stain from past oozing), loose bark, or dark cankers, call an arborist as soon as possible. Consider planting healthy butternut trees on your property to keep the species alive (however, this would require you to pay very close attention to the health of the tree).

Black Knot

Black knot is caused by an infection of the fungus Apiosporina morbosa. This tree bark fungus causes tarry, black swellings on branches that can slowly kill tree limbs. It is now widespread throughout Canada, and infections can rip through fruit tree populations like cherry, plum, and apricot. Because these swellings start as small green growths, it can be easy to miss the fungus; it can take two or three years for the swelling to turn black and release their spores. Black knot doesn’t just cause aesthetic problems, and if the infection is let alone, it can kill the branches and the tree.

To combat black knot, it’s important to prune the infected branches during late fall, winter, or early spring, when the trees are dormant. Proper disinfection of the blades used to prune the trees is important, as infected equipment can spread the fungus; call an arborist when you notice black knot on your trees.

Black Rot

Another ominous disease that affects fruit trees in Ontario, black rot is caused when the bark of hardwood fruit trees is infected by the fungus Botryosphaeria obtusa. This fungus gets into plum and apple trees through wounds in bark caused by insects, natural stressors, and/or improper pruning. It causes cankers that first appear on limbs as reddish-brown discolouration in the bark; starting out small, these cankers can get up to 50 centimetres in length along the infected limb, cracking the bark and killing it. As time passes and the cankers get worse, the wood turns black and shrinks, causing the bark to peel back. The limbs weaken and may break from the weight of the fruit. Infections on the main trunk, particularly on young trees, can weaken and kill trees prematurely.

Black rot is a serious scourge to orchards, and should be dealt with as vigorously as possible. It’s important to prune out diseased limbs ASAP and remove the clippings from the property, as black rot can survive on dead tissue. Fire is the best tonic for this wood! Woodpiles can be a major source of black rot so they shouldn’t be on or near fruit orchards. If there’s a spread of the fungus, try to locate surrounding woodlots and see if there are hardwood trees infected with the disease. Do your best to remove and burn these trees to decrease the spread of disease (of course, with permission from the potential owner and under safe conditions!).

Identifying Tree Diseases

July 28, 2016

Diagnose Your Tree Disease

Get a grip on what’s plaguing your tree with our visual overview of 10 common tree diseases. (Most likely, it’s a fungi.) In future blog posts, we’ll discuss treatment and control methods for tree diseases so that you can gain the upper hand in the situation.

What Causes Tree Diseases?

Witnessing the slow death of a beloved tree is sad for any homeowner, hobbyist or professional. Trees can acquire diseases, just like people and animals do.
The good news is, tree diseases don’t have to be a death sentence, if they are stopped in time. Many diseases can be treated as soon as the bacterial or fungal culprit is identified. For serious cases, you should hire a professional to treat the tree or, if it’s too late, remove it from your landscape before it becomes a hazard.

Common Tree Diseases in Pennsylvania

Here are some of the tree diseases most common to Pennsylvania.

Leaf Diseases

  • Decidious trees, those that lose their leaves seasonally, can develop leaf spot diseases. These tree diseases debilitate trees and shrubs by interrupting photosynthesis, the process by which plants creates food and energy.
  • Anthracnose – Anthracnose is caused by a group of fungus species. In Pennsylvania, it most often affects ash, oak, sycamore, maple and dogwood trees. Symptoms include leaf spots, blotches or distortion, especially along leaf veins, defoliation, shoot blight, twig cankers and dieback. A sure-fire way to determine if your tree suffers from this is to use a magnifying glass to examine the underside of an infected leaf. You will see pimple-like fungal fruiting structures, especially along the leaf veins. Fortunately, most of the time, anthracnose does not cause long term damage to established trees. But repeated infections with anthracnose over consecutive years will reduce the tree’s health and leave it vulnerable to other pests and infections.

Bark and Trunk Diseases

  • Beech Bark Disease affects beech trees and is caused by the combination of a beech scale insect’s feeding habits and an opportunistic fungal pathogen. An early sign of beech bark disease is a visible infection on the tree’s bark that looks like a reddish-brown, oozing, bleeding wound. (Yuck!) Other symptoms of the disease include small, sparse, yellow foliage, and a thin, weak crown.
  • Thousand Cankers Disease – Like the beech bark disease, thousand cankers disease is caused by a bug/fungus double whammy. A tiny bark beetle creates galleries and tunnels beneath the bark of the tree and paves the way for a fungal infection and cankers. The three primary symptoms of this disease are dead branches, many small cankers on branches and the trunk, and evidence of tiny bark beetles. The bark surface may not seem affected, or a dark amber stain or cracking of the bark may appear directly above a canker.
  • Dutch Elm Disease – Dutch Elm Disease destroys the American elm tree and some other elm species. It is caused by a fungus that infects the vascular (circulatory) system of the tree. The fungus clogs vascular tissues, prevents water movement to the crown and causes the tree to wilt and die. Initially, the disease will affect individual branches, causing leaves to yellow and curl up. Within one to three years, it will choke and kill the entire tree.

Root diseases

  • Root Rot – Armillaria root rot is a fungal disease affecting hundreds of species of trees and fruit and vegetable plants. Oak and dogwood trees are particularly vulnerable to the fungus. It’s most common when soil remains wet for long periods. Symptoms may not be immediately evident; the tree may decline gradually over a few years. Leaves may turn a dull green, yellow, red, or purple as they wilt. The bark of infected trees may appear darkened around the soil line. Peeling away some bark should reveal red-brown discoloration underneath.
  • Black Knot – Black knot is a disfiguring and ultimately deadly disease that infects stone fruit trees, particularly plum and cherry trees. It’s caused by the fungus Apiosporina morbosa. Black knot’s presence is most obvious in winter when there are no leaves to hide the fungus’ trademark bulbous, warty black masses on tree branches. The mass usually encircles the stem, and it can range from an inch to nearly a foot in length. Older knots can become infested and covered with a pinkish-white mold.

Preventing Tree Diseases

Avoid tree diseases by educating yourself on the common types of problems in your geographic location. Purchase and plant trees that are resistant to the area’s problematic agricultural diseases. And as always, practice good tree care maintenance. Regularly monitor the tree’s fertilizer, light, soil, and watering conditions, and you will help keep disease at bay.

Ask the Experts about Tree Diseases

If you have any questions or want help bringing your beloved tree back to its full glory, contact Elite Tree Service at 610-935-2279.

Common Tree Fungus

Tree Fungus is a common ailment for trees. When fungal spores come in contact with a susceptible host they begin to grow, enter, and feed on the tree or shrub.

Not all fungi growing on your tree are harmful; some do not affect the tree at all while others are even beneficial. It’s best to have an arborist diagnose what type of fungus is growing on your tree. The arborist will be able to let you know if the fungus is harmful and be able to recommend appropriate treatments.

How A Tree Fungus Spreads:

Tree fungi produce spores that spread and infect other trees or shrubs.

Spores spread through:

  • the air on windy days
  • hard rains that splash the spores up onto trunks and leaves
  • gardening tools
  • Human movement; for example, walking through wet diseases plants then walking through healthy plants that aren’t yet infected.

Signs Of A Fungal Disease:

You may see mushrooms or other types of fungi growing on or around your tree if you have a fungal disease. However; many times the tree fungus may not appear above ground or many have a different appearance than you would expect.

The symptoms you see will depend on what type of tree fungus is attacking your tree. In most cases being infected with a tree fungus will result in loss of vigor and discoloration or wilting of leaves.

Tree Fungus Treatments:

Once infected with a tree fungus your tree or shrub can never be fully cured. However; it can be treated. Our arborist will recommend a plan to suppress the tree fungus. This will stop the disease from getting worse and to restore your tree’s health and vigor.

If the fungus is too far developed, the arborist may recommend removing the tree/shrub and replacing it with a fungi resistant species.

Prevention is key when it comes to fungus.

To prevent infection:

  • Don’t over water
  • Make sure your soil drains properly
  • Boost overall health with proper maintenance
  • Sanitize gardening tools between plants
  • Rake and remove falling leaves from your yard
  • Use preventative fungicides

Need Help With A Tree Fungus?

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Common Tree Fungi

Diseases caused by a tree fungus are separated into four categories, root and butt rot, canker, foliar/shoot, and wilts.

Root Rot Diseases:

Root rot diseases are caused by fungi that are found in the soil and attack the roots of plants.

Armillaria Root Rot:

Also known as Oak root fungus, is a disease caused by the fungi of the genus Armillaria. If left untreated it will cause rapid decline and death. In the worst cases, when left untreated trees can become structurally unsafe and uproot or snap possibly causing property damage and injury.

Symptoms: Dulling of leaf color, loss of vigor, leaves turn yellow or brown, leaves wilt.

Targets: This tree fungus has an extremely wide range of hosts. Most trees and shrubs are susceptible to root rot.

Learn more about Armillaria Root Rot

Phytophthora Root Rot:

Phytophthora Root Rot is an extremely damaging and widespread fungus like organism that will rot away root systems and eventually kill your tree if left untreated. In the worst cases, when left untreated trees can become structurally unsafe and uproot or snap possibly causing property damage and injury.

Symptoms: Suppressed growth, yellow or undersized needles/leaves, dieback, drooping and curling of leaves, leaves turning brown.

Targets: Wide range of plants. The most susceptible include Azalea, rhododendron, dogwood, pieris, yew bushes, deodar cedar, mountain laurel, heather, juniper, Fraser fir, white pine, shortleaf pine, camellia japonica, aucuba.

Learn more about Phytophthora Root Rot

Canker Diseases:

Canker Diseases are caused by fungi that commonly enter the tree through wounds in the bark or branch stubs. Improper pruning can increase your risk of cankers.

Thousands Canker Disease:

Originally confined to the western parts of the United States, Thousands Canker Diseases, made it to Fairfax County in 2012. The tree fungus, Geosmithia morbida, is spread by the Walnut Twig Beetle. These fungi develop cankers under the bark so cankers will not be visible.

Symptoms: Thinning canopy, discolored leaves, small leaves, individual branch dieback.

Targets: Black Walnuts but all species of walnuts may also be susceptible.

Learn more about Thousands Canker Disease

Phytophtoria Bleeding Cankers:

Caused by various species of the Phytophtoria fungi, bleeding cankers are wet looking, oozing areas on the trunk of ornamental and shade trees. These cankers impact the vascular system of the tree, inhibiting important energy transfers.

Symptoms: Reddish-brown fluid oozing from a crack in the bark, above the infected area, foliage may be pale and sparse and branch dieback may start to occur, and a strong alcohol, fermenting smell that attracts insects to the infected areas of the tree.

Targets: Most ornamental and shade trees; however, beech, maple, and oak tend to be highly susceptible.

Learn more about Phytophtoria Bleeding Cankers

Cytospora Canker:

Also known as Leucostoma canker, this tree fungus is one of the most damaging diseases of spruces. This fungus grows throughout the inner bark causing the portion of the tree behind the canker to die.

Symptoms: Death of branches starting at the base of the tree moving upward. Cankers aren’t very noticeable, with little to no bark deformation. Needles on infected branches turn grayish and brown.

Targets: Colorado Blue Spruce (and it’s varieties), Norway spruce, koster’s blue spruce, white spruce, Douglas fire, and other spruces.

Learn more about Cytospora Canker

Hypoxylon Canker:

This tree fungus negatively affects growth and can lead to the death of the tree. This fungus is typically a secondary invader; meaning that it usually does not infect healthy hardwoods but targets stressed or injured trees.

Symptoms: At first the cankers show up as light brown or tan and look dry and dusty. Within a few weeks they will turn silvery gray with scattered black spots.

Targets: Hardwoods but has three primary species. Hypoxylon atropunctatum found on Oaks, Hypoxylon mammatum found on Aspen, and Hypoxylon tinctor found on Sycamores.

Learn more about Hypoxylon Canker

Foliar Diseases:

Foliar diseases are very common and caused by fungi that attack the leaves of the tree or shrub.

Cercospora Leaf Spot:

The tree fungus begins as a small spot on the leaves. As the disease progresses more spots appear until the leaf ceases to function as the site of the tree’s food production process and falls off of the tree.

Symptoms: Round leaf spots (may have purple or dark brown borders), tiny black flecks (fungal spores) in the center of the spots.

Targets: Wide range of ornamentals, shade trees, and plants. Our Arborists report that White Oaks are especially susceptible in our area.

Learn more about Cercospora Leaf Spot


Anthracnose is a tree fungus that is active in the spring when the weather is wet and cool. Overwintering in fallen leaves, this fungus will continue to infect your tree year after year if not treated. Multiple infestations can leave trees stressed and susceptible to secondary invaders.

Symptoms: tan to brown leaf spots which many have purple rings around them, wilting, defoliation, dieback, leaf blotches.

Targets: Dogwoods, Ash, Oak, Sycamore, Birch, Walnut, Tulip, Hickory, and Maple

Learn more about Antracnose

Sooty Mold:

Sooty mold is a fungus that grows on top of honeydew (the excrement of plant-sucking insects) and coats the leaves to the point where they can no longer absorb sunlight. This interrupts photosynthesis and the tree will not be able to produce the nutrients they need for survival. If your trees and shrubs are turning black you most likely have a sooty mold problem caused by an insect infestation.

Targets: Typically seen on rose, ash, oak, elm, maples, willow, and fruit trees.

Powdery Mildew:

Powdery Mildew is a tree fungus that coats leaves blocking the process of photosynthesis. Every year trees and shrubs rely on photosynthesis to create food for new leaf growth. When this process is interrupted by powdery mildew the food reserves aren’t replenished and the tree/shrub’s growth will be stunted which can affect overall health. The stress caused by Powdery Mildew also makes the tree more susceptible to other diseases and insect infestations.

Symptoms: Powdery mildew is characterized by spots or patches of white to grayish, talcum-powder like growth on the upper side of leaves.

Targets: A wide range of plants but Lilacs, Peonies, Dogwoods, or Crape Myrtles are especially susceptible in this area.

Learn more about Powdery Mildew

Shot Hole Fungus:

This tree fungus is commonly mistaken for insect damage because of the BB-sized holes it leaves. This fungus will stress your plants and should be treated to keep secondary invaders away.

Symptoms: Brown or reddish-brown leaf spots, holes in leaves where the leaf spots used to be, yellow leaves dropping in mid-summer.

Targets: Cherries and Cherry Laurels

Wilt Diseases:

Wilt diseases are caused by fungi that invade a tree’s vascular system. With the vascular system compromised the tree cannot transport water and nutrients throughout itself.

Verticillium Wilt:

Verticillium Wilt is caused by the soil-borne fungi Verticillium albo-atrum and Verticillium dahliae. The tree fungus invades through the roots then spreads through the plant’s vascular system. Once the Xylem, the tree’s water transportation system, is infected it becomes clogged and water can no longer reach the tree’s leaves. Verticillium is common and affects several hundred species of trees and shrubs.

Symptoms: Leaf curling, drying, small yellow foliage, leaf scorch, and slow growth. Often times the symptoms are seen on one side or section.

Targets: Ash, Azalea, Cherry, Certain species of Dogwood or Linden, Locust, Magnolia, Maple, Oak, and Redbud.

Learn more about Verticillium Wilt

Oak Wilt:

Oak wilt is a disease that targets oak trees and is caused by the fungus Ceratocystis fagacearum. Spread through insects and connections between roots, there are no resistant or immune oak species. This illness was first found in 1944 in Wisconsin but has now spread to 21 states. Oak wilt is devastating and can kill rapidly within a single season.

Symptoms: Leaf discoloration, wilt, defoliation, and ultimately the death of the tree from the top down.

Targets: All species of oaks. Red oaks succumb to the diseases faster than white oaks.

Learn more about Oak Wilt

Dutch Elm Disease:

Dutch Elm disease, one of the most destructive shade tree diseases in North America, is caused by a fungus spread by the elm bark beetle. First reported in the U.S in 1928, the disease is believed to have been brought over from the Netherlands in a shipment of logs. Out of the 77 million elms in North America in 1930, over 75% had been lost by 1989. To this day, the Elm population across the United States is still battling this toxic disease.

Symptoms: Dutch Elm Disease causes leaf wilting, curling and yellowing of leaves, leaf drop, and will kill your tree.

Targets: Elms

Learn More About Dutch Elm Disease

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