Tree fungus can be a persistent and troublesome issue for arborists, landscapers, and tree enthusiasts alike. It not only affects the aesthetic appeal of your trees but can also pose significant risks to their overall health. Tree fungus types, causes, Symptoms, and treatment will be covered in this thorough reference. To keep your trees healthy and beautiful for years, we’ll teach you how to manage and avoid tree fungus.
Understanding Tree Fungus
Many forms of fungus can damage trees, known as tree fungi. Tree fungus can attack leaves, branches, stems and roots. It is important to understand the types of tree fungus to fight it:
Types of Tree Tree fungus disease
Tree fungus is a term that refers to various types of fungal infections that affect different parts of a tree. Some tree fungi are harmless, while others can cause serious diseases that can kill the tree or make it look unsightly. Tree fungus can be identified by its shape, color, texture, location, and symptoms on the tree. Some common types of tree fungus are:
Yellow tree fungus
Trees affected: Pines, firs, Spruces, Oaks, Maples, and Eucalyptus
Symptoms of yellow tree fungus are: The appearance of bright yellow fruiting bodies that look like mushrooms or brackets on the infected parts of the tree, such as branches, trunks, or roots. The decay and rotting of the wood, which may become soft, spongy, or crumbly. The reduced growth and vigor of the tree, which may show signs of wilting, yellowing, or dying of leaves and branches. The increased susceptibility of the tree to other pests and diseases, such as bark beetles or wood borers.
Causes of yellow tree fungus are:
- The fungus flourishes in damp and humid circumstances caused by overwatering, inadequate drainage, or rains.
- The fungus eats dead or rotting wood in the soil or on trees. Rotting plants may attract insects that transmit fungal spores.
- The fungus loves shaded and dark environments produced by thick vegetation, overgrown branches, or surrounding buildings.
- The fungus may develop in compacted soils, reducing tree roots’ oxygen and nutrient availability.
- Fungus spores may travel far and infect new hosts. Animals, insects, wind, and humans may carry spores.
- The fungus may develop on low-quality or polluted fertilizers, which supply organic matter or nutrients. Fertilizers may change soil pH or salinity, affecting tree health and resilience.
Season: It usually appears in late summer or early fall, when the temperature and humidity are high.
Treatment: After infecting a tree, yellow tree fungus is incurable. Good cleanliness and sanitation around the tree is the greatest prevention. Avoid hurting the tree with tools or equipment, remove dead or rotting wood, dispose of old food and feces, and prune diseased branches using clean, sharp tools. Growing resistant or tolerant tree species may also lower infection risk.
Anthracnose
Trees affected: Ash, Maple, White oak, Sycamore and Walnut
Symptoms of Anthracnose: Brown or black leaf spots or lesions are the most common anthracnose sign. The spots may merge and cover vast portions of the leaf, curling, wilting, or falling off prematurely. Some kinds of anthracnose may infect host plant fruits including tomatoes, grapes, and walnuts. Anthracnose may also harm host plant buds, shoots, and flowers. Infected areas may perish and become black or brown. Dieback may impair plant growth and output.
Causes of Anthracnose:
- Anthracnose-causing fungus include Colletotrichum, Gloeosporium, Discula, Gnomonia, and Apiognomonia. Host-specific fungus only infect particular plants.
- The fungi’s spores may live in soil or plant detritus. The spores may spread by wind, water, insects, animals, or humans. Spores may enter the plant via leaf, stem, fruit, or flower wounds.
- Moisture and warmth help fungus grow and germinate. Wet times, such as rainy seasons or overhead irrigation, worsen the illness. Plant age, health, and resistance affect infection.
Season: Anthracnose is more likely to occur in spring and early summer, when the weather is cool and wet, and the new growth of the plants is susceptible to infection.
Treatment: Remove and burn dead twigs. Remove any leaves near vulnerable trees. Fungicides should be used weekly or biweekly from bud break until daily temps reach 60 degrees, according to the PennState Extension.
Canker diseases
Trees affected: It can affect many trees, such as pines, spruce, willows, poplars, oaks, maples, cedars, yews, and more.
Symptoms of Canker diseases : The affected tree may lose its leaves early, particularly in autumn and winter, exposing the bare branches to frost damage. Due to the canker obstructing vascular tissue, diseased branches’ leaves may droop or curl, signaling water shortage. The tips of diseased branches may die back with brown or black necrotic tissue. Also, the afflicted tree may have slower growth, smaller leaves, fewer blossoms, and less fruit. Darkened or sunken regions with a border may appear on diseased bark. Lesions vary in size, shape, color, and texture depending on the canker and host tree. The diseased bark may separate, revealing the wood and sapwood.
The afflicted tree may discharge sap or resin from the canker location as a defense or due to bacterial fermentation. Depending on the canker and host tree, sap or resin may be clear, white, yellow, brown, red, or black.
Causes of Canker diseases:
- Exposure to extremely high or low temperatures
- Flooding and drought Summer or winter sunscald, hail, high winds
- Nutritional imbalances and soil compaction
- Mechanical injuries (lawn mower, vehicles) and animal damage
- Pruning wounds
- Root rot and insect borers
- Improper planting
Season: During the growing season, periods of moisture stress, are more severe during hot and humid weather, winter or summer sunscalds, hail, or high winds
Treatment: Its depends on the type and severity of the infection. First Pruning out the infected branches or limbs can help prevent the spread of the disease to other parts of the tree or nearby trees. Pruning should also be done during the dormant season or when the weather is dry to reduce the risk of infection. Applying fungicides or bactericides can help control some types of canker diseases by killing or inhibiting the growth of the pathogens.
However, fungicides or bactericides cannot cure existing cankers and may not be effective against all types of pathogens. Wound dressings are substances that are applied to the pruning cuts or wounds to seal them and protect them from infection. Wound dressings may also crack or peel off over time and expose the wound to more infection. Therefore, wound dressings should be used sparingly and only when necessary.
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Needle blight
Trees affected: It affects the needles of coniferous trees, especially pine.
Symptoms of Needle blight:
- The infected needles may fall off the tree before their normal lifespan, leaving the branches bare or with only a few needles at the tips.
- The infected needles may change color from green to yellow, tan, brown, or reddish-brown.
- The infected needles may develop spots or bands of different colors, often with distinct margins or cut-off lines.
- The infected needles may show small, black fruiting bodies on their surface or inside their tissue. These are the reproductive structures of the fungi that cause needle blight.
Causes of Needle blight
This disease causes yellow to tan spots in the fall, which turn brown then reddish-brown and continue up to the tips of the needles. There’s an obvious cut-off line between the infected tissue and the needle base, which stays green at the needle base.
These diseases cause premature needle defoliation, resulting in loss of timber yield and, in severe cases, tree death. They are caused by different fungi that infect the needles through wounds or natural openings. The fungi form small, black fruiting bodies on the needles that release spores in wet weather. The spores then land on another host tree and start a new infection cycle.
Season: During the growing season, periods of moisture stress, are more severe during hot and humid weather, winter or summer sunscalds, hail, or high winds
Treatment: Selecting resistant varieties of pines for planting. Avoiding injuries to the trees by protecting them from mechanical damage, pruning correctly and at the right time, and sanitizing pruning tools between cuts.
Maintaining proper cultural practices such as watering, fertilizing, mulching, and spacing. You can applying protective fungicides in spring or fall as a preventive measure or in combination with pruning. Removing severely infected trees to prevent further spread.
Tar spot
Trees affected: Tar spot particularly affects the leaves of maple and sycamore.
Symptoms of Tar spot
Causes of Tar spot: This fungal disease causes black spots that look like tar on the leaves, usually surrounded by a yellow border. Tar spot does not harm the health of the trees, but it may make them look unsightly and cause some early leaf drop. Tar spot is caused by different fungi in the genus Rhytisma, such as Rhytisma acerinum, Rhytisma americanum, and Rhytisma punctatum.
Season: Tar spot is more noticeable during fall or during cool and wet weather
Treatment: These fungi survive in the fallen leaves and produce spores in the spring that infect the new leaves. The spots develop over the summer and become more noticeable in the fall. To prevent and control tar spot, it is recommended to rake and dispose of the infected leaves in the fall, or compost them at high temperatures. Fungicides are usually not necessary or effective for this disease.
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Sooty mold
Trees affected: Sooty fungus is found on many deciduous and evergreen shrubs and trees
Symptoms of Sooty mold
The most obvious symptom of sooty mold is a black, sooty coating on the leaves and fruits of affected plants.
This fungus obtains nutrition from honeydew, a sweet, sticky substance secreted by insects. These pests include aphids, mealy bugs, scales, and whiteflies.
On the leaves, this layer of fungus blocks sunlight and reduces the leaves’ ability to produce food.
Causes of Sooty mold
Sooty mildew commonly occurs on trees and shrubs, with honey insects causing great damage. Honeydew, unless washed away by rain, will stick to the plant. Wind carries sooty mold spores into the honeydew, which can then grow and develop into honeydew.
As the spores germinate, they produce black fungal threads, called mycelial threads, which cause a black sooty coating.
Season: Sooty mold is more noticeable during fall or during cool and wet weather
Treatment:
When treating sooty mold, it is important to target these harmful insects. At the first sign of aphids, mealy bugs or whiteflies, Cornell University Cooperative Extension recommends spraying the insecticide malathion. Follow all labeled product directions for best results.
You can wash sooty mold off plants, but unless you control honeydew insects, sooty mold will reappear.
Shoot fungus
Trees affected: Since this fungus shoots its spores into the air, they are transported by the wind and cling to plants and homes. Shoot fungus affects Apples, Pears, Olives, and Citrus.
Symptoms of Shoot fungus
The most common symptom of shoot fungus is the presence of spots on the leaves and fruits of the affected trees. The spots may vary in color, size, shape, and location depending on the type of shoot fungus and the host tree. The spots may be brown, black, yellow, or red, and may have distinct margins or blend with the surrounding tissue. The spots may be circular, oval, irregular, or blotchy, and may cover large or small areas of the plant surface. The spots may appear on one or both sides of the leaves and fruits.
The spots caused by shoot fungus can reduce the amount of light that reaches the plant surface, which can interfere with the photosynthesis process. Reduced photosynthesis can affect the growth and health of the trees. The spots can also make the fruits look unattractive and less marketable, which can reduce their quality and yield.
Causes of Shoot fungus
The causes of shoot fungus are different fungi that infect the leaves and fruits of the trees through wounds or natural openings. It causes the shoots to die back and turn black or brown. It can also cause lesions on the fruits and leaves. Shoot fungus can reduce the yield and quality of the fruits and weaken the tree. The fungi which form small, black fruiting bodies on the plant surfaces that produce spores that are released into the air.
Season: The spore discharge can occur at any time of the year, but it is more noticeable in spring or fall when the weather is cool and moist.
Treatment:
Some varieties of trees are more resistant to shoot fungus than others. Selecting resistant varieties can help reduce the incidence and severity of shoot fungus in your landscape. You can consult your local nursery or extension service for recommendations on resistant varieties for your area. Secondly, you can Maintaining proper cultural practices such as watering, fertilizing, mulching, and spacing can help improve the health and vigor of your trees and make them less susceptible to stress and infection.
Last but not least you can Apply protective fungicides in spring or fall can help control shoot fungus by killing or inhibiting the growth of the fungus. However, fungicides cannot cure existing infections and may not be effective against all types of shoot fungi. Therefore, they should be used as a preventive measure or in combination with pruning.
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Root rot
Trees affected: True fir, Douglas-fir, spruce and eastern white pines are highly susceptible to root rot. Some species of cedar, especially Turkish and waxy, are trees that show some tolerance.
Symptoms of Root rot
Trees that rapidly develop reddish-brown needles and exhibit dieback may have Phytophthora root rot. Symptoms include reduced or stunted growth, reddish-brown needles, needle loss, root rot, or bleeding cankers.
Causes of Root rot
Root rot is a soil-borne fungal disease that spreads from an infected area to a healthy area through soil or surface water. During cold or dry periods, resting spores called chlamydospores and oospores develop. These spores can survive for many years in the soil or plant.
When temperatures exceed 59 degrees, these spores germinate and form spore-producing structures called sporangia, which release zoospores. These zoospores can float for up to an hour in soil water to find vulnerable roots or float in surface water to a healthy area.
These spores then enter the plant’s roots and form infectious mycelium. As the mycelium spreads into the roots and stem, the tissue will rot and prevent essential nutrients from reaching the rest of the tree.
Season: New infections may occur if the temperature exceeds 59 degrees.
Treatment:
- It is essential to practice preventive measures as there is no cure for this disease.
- How to protect your trees from Phytophthora root rot:
- Buy and plant only healthy plants from a registered grower.
Do not plant trees in fields known to be infected. - If your nursery plants have red-brown roots or other symptoms of Phytophthora root rot, do not plant them.
- Avoid over-fertilizing or over-watering your trees.
What to Do if Your Tree Has a Fungal Disease?
If you are concerned about a possible fungal disease plaguing your beloved tree, I sincerely recommend reaching out to a certified arborist in your vicinity. Timeliness is of the essence when it comes to dealing with tree diseases, as the consequences of delay can be extremely serious. Left unchecked, deadly fungal infections can spread rapidly, wreaking havoc on the vitality of your otherwise robust arboreal inhabitants and significantly damaging the aesthetic integrity of your carefully nurtured landscape.
An experienced arboricultural specialist has the requisite expertise to administer effective fungicide treatments, perform proactive horticultural interventions and, when necessary, execute the safe and careful removal of any trees affected by the infestation. I urge you not to put off the call for arboreal assistance, as delay may tragically result in the irreparable death of your dear arboreal companion.
