![]() ![]() The symptoms usually first appear on lower branches and then spread upward.įigure 4. If infection is severe, branch cankers and twig dieback can occur during winter and early spring. Mature leaves are fairly resistant and the symptoms are simple necrotic spots. On the underside of an infected leaf, tiny brown fungal fruiting bodies may be visible on or near major veins. Old lesions are papery and gray to white in color (Figure 4). Large lesions often follow leaf veins or are delimited by leaf veins (Figure 3). Young leaves become cupped or distorted with necrotic lesions. Blighting causes leaves and shoots to brown and shrivel. Shoot blight is one of the first symptoms seen in spring. Symptoms vary with host, weather and time of infection. Rake fallen leaves and debris and discard to reduce disease inoculum. Spores causing oak leaf blister are spread by wind and rain. The disease develops during wet, humid, mild conditions in the spring. The pathogen can survive winter on plant twigs and bud scales. Leaves become infected when buds are beginning to open in the spring. All oak species are susceptible to this disease.įigure 2. Trees are not severely damaged, but the appearance of the tree may be unsightly. As the disease progresses, the blisters turn brown and the leaf will curl as the blisters coalesce. The lower surface has gray depressions that correspond to the raised blisters. Oak leaves begin to show chlorotic, blister-like areas on the upper surface that can be as large as one half inch in diameter (Figures 1 & 2). Tree is newly transplanted leaves turn brown, bark on lower stem may peel away Conks or mushrooms growing at root collarġ1. Established tree in slow decline, white or thread-like material under barkġ1. Sour- or yeasty-smelling sap oozes from trunk trunk stains darkġ1. Black, crusty, small spots or vertical stripes on trunk or branchesĩ. Branches show flagging, wilting foliage yellows or brownsĩ. Branches show dieback cankers on trunk tree in declineĨ. Black, sooty or powdery growth typically on upper leaf surfaceĨ. Upper or lower surfaces of leaf with white, powdery growth pale green spots may also be present when growth is absentħ. ![]() Small, yellow pin-point spots on upper leaf surface brown, hair-like projections on leaf undersideħ. Light green, puckered areas in the spring areas become necrotic in fallĦ. Leaves and/or twigs with mycelium on upper or lower surfaceĦ. Yellow, brown or dull green scorching from leaf tip toward petiole or beginning at leaf petiole affected branch often wiltsĦ. Scorching from leaf tip toward petiole yellow to red line often precedes advancing scorch symptom on leafĥ. Sprawling spots seen in the fall often with yellow haloĥ. Spots seen in the spring leaves are tattered or distorted twigs killedĤ. Marginal, tip or interveinal leaf scorching affectes all leaves on a branchĤ. Tan, crusty spots associated with leaf puckering seen in the fallģ. Tiny to sprawling brown or gray spots along leaf margins and/or veins no leaf blistering or puckering associated with spotsģ. ![]() Necrosis absent leaves affected but remain greenģ. Leaf necrosis (dead spots or blights) presentĢ. The following key will help you identify common diseases of oak trees. from "Florida Tomato Scouting Guide", University of Florida. In order to use these keys, you must first decide or make an educated guess as to whether the damage or symptom is caused by an INSECT or DISEASE." The choices describe symptoms or morphological characteristics thought to be most distinctive of a particular insect or disease. It is based on a series of questions that have as answers choices between two or more alternative pathways. "'What is an "identification key?' It is a road map of sorts that aids in the identification of a disease or an insect specimen observed in the field. ![]()
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