Oak Tree Diseases

Oak Tree Diseases

Oak Tree Diseases

Anthracnose

 

  • Symptoms

    • During wet weather, young leaves are blighted as bud break occurs or large dead areas form between the leaf veins primarily on lower branches. Winter twig dieback may occur. Slightly raised, brown dots (fungal fruiting structures) form on the lower surface of leaves and on dead twigs. Often, these can be seen without a magnifying glass. However, magnification helps greatly in finding these small structures.

 

  • Management

    • Only highly valued trees should be treated with a fungicide to protect new twigs and leaves as they form. Otherwise, prune and destroy dead twigs and branches during dormancy. Apply chlorothalonil, copper sulfate, copper hydroxide, or mancozeb.
Oak Tree Disease Anthracnose

Anthracnose

 

Armillaria Root Rot

 

  • Symptoms

    • Branches die back. A fleshy, firm, honey-colored mushroom forms annually in the autumn in groups of a few to 100 or more in a cluster at the tree base. The cap of the mushroom is 1½ to 6 inches in diameter with a slightly depressed center and may have brown, scale-like spots. Although the cap is usually dry, it may be slimy after a rain. Its stem is ½ to 1 inch thick and may be 2 to 6 inches long. The spores are formed on flat, plate-like structures (gills) on the underside of the cap. A white fan of fungal growth is often found just under the bark at the base of the infected tree.

 

 

Bacterial Leaf Scorch

 

  • Symptoms

    • Browning of the oldest leaves along their margins begins in mid to late summer on one branch or a few branches on inner and lower portions of the tree. A wavy, reddish-brown band sometimes develops between the brown and green tissue of the leaf. The browning of leaves progresses to include more leaves toward the ends of branches. Branches and eventually entire trees die.

 

 

Oak Tree Diseases - Bacterial Leaf Scorch

Bacterial Leaf Scorch

 

Bacterial Wetwood

 

  • Symptoms

    • Dark streaks of sap, usually foul smelling, ooze from holes or cracks in the bark. The heartwood is discolored dark brown. Pin oaks are especially prone to wetwood.
  • Management

    • Avoid wounding the bark of affected trees. Care for the tree as normal, minimizing any stresses.

 

Ganoderma Root Rot

 

  • Symptoms

    • A butt rot may take several years to kill the tree but makes the tree very susceptible to wind-throw. A distinctive shelf-like fruiting structure forms singly on the wood at or near the soil line. It is brown to reddish brown on top with a cream to white margin. The brown portion appears to have been varnished. The shelf grows perennially for 5 to 10 years and may reach 8 to 12 inches across. The underside of the shelf is light colored with tiny pores in which the spores are formed. The underside turns brown where scratched and forms an interesting drawing surface, thus the common name “artist’s conk.” Infected trees slow in growth rate and have dying branches with small, yellowed leaves.

 

  • Management

    • Although it may require several years for the tree to die, an infected tree poses a hazard. A tree with fungal fruiting structures on it should be removed promptly if it is in a location where property damage may occur or where people or pets could be struck by falling limbs or the falling tree.
Oak Tree Diseases - Ganoderma

Ganoderma on Oak Tree – Early in Development

Oak Tree Diseases - Ganoderma

Ganoderma on Oak Tree – well Developed Shelf

 

Inonotus Root  Rot

 

  • Symptoms

    • A root and butt rot develops. Trees may topple before any obvious symptoms are noted. Infected trees often have branch dieback and fewer than normal leaves that are yellowed. Although the root rot begins well out on the root system, the fungus eventually reaches the butt of the tree where it forms large, tough, irregularly shaped, light- to dark-brown shelves at or just above the soil line. With age, these become very rough and dark brown to black. Cutting the shelf reveals a reddish-brown center. The underside of the shelf is brown with tiny pores in which the spores are formed. A sure sign of severe damage to the tree is the presence of the fruiting structures.

 

  • Management

    • Infected trees should be removed immediately
Oak Tree Diseases - Inonotus

Inonotus Early in the Fall

Oak Tree Diseases - Inonotus

Inonotus – Late in the Fall

 

Laetiporus Root Rot

 

  • Symptoms

    • Massive clusters of bright sulfur-yellow to salmon to bright-orange, shelf-like fruiting structures that turn white with age initially form in the summer or autumn on the wood of the tree but fall off during the winter. The underside of the fruiting structure has tiny pores in which the spores are formed. New shelves form on the wood the following summer and autumn. The bark where the fruiting structure forms is slightly depressed and cracked.
  • Management

    • Fruiting structures form long after most of the damage has been done. Infected trees are very prone to wind breakage even before the fungus begins to form fruiting structures and should be removed at the first sign of infection.

 

Oak Tree Diseases - Laetiporus Sulfurous

Laetiporus Sulfurous

 

Leaf Spot

 

  • Symptoms

    • In mid- to late summer, irregular, dark-brown spots form between the leaf veins and enlarge up to 3/8 inch in diameter and become reddish brown, often with a yellow halo. Trees with iron chlorosis and those under other stresses are most severely affected

 

 

Oak Tree Diseases - Leaf Spot

Tubakia Leaf Spot

 

Powdery Mildew

 

  • Symptoms

    • White fungal growth develops on the upper surface of leaves in the late Summer and Autumn

 

 

Oak Leaf Blister

 

  • Symptoms

    • Spots ¼ to ½ inch in diameter turn light green as young leaves expand. Leaf cells in the spots multiply more than surrounding cells, and a raised blister-like buckling of the leaf results. As the spots age, their upper surface becomes covered with a buff white coating of fungal growth that later turns brown. The leaves usually do not fall prematurely.

 

  • Management

    • Fungicide application in the landscape is not necessary because the leaves are seldom severely spotted and do not fall prematurely. Although infections may be extensive some years, little damage actually results. In the nursery, chlorothalonil or mancozeb must be applied late in dormancy prior to bud break to prevent spotting. Once bud break has occurred and symptoms are visible, it is too late to spray.
    • Click Here to learn more about Oak Tree Leaf Blisters

 

Oak Tree Disease - Blisters

Oak Leaf Blisters

Oak Tree Diseases - Blisters

Oak Leaf Blisters

Oak Wilt

 

  • Symptoms

    • Most oaks but especially red oaks are susceptible. White oaks tend to be resistant. Leaves at the top of the tree turn brown along the tips and margins, wilt, and soon begin to fall while there is still some green color left in them. This damage progresses down the tree. Twigs and branches die. Brown streaks often observed in the outer sapwood are sometimes difficult to find. Trees usually die within a year after infection.

 


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