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Plant NameTypeDescription 
Collar rot (Phytophthora)MadroneDiseaseCollar rot is caused by a fungus which lives in soil. Leaves of infected trees may be discolored, stunted or may die. Cankers occur near the trunk base, and appear sunken, brown or black, and water soaked. Margins of the cankers are definite and may exude a dark fluid. Dogwood, maple, and other trees also contract collar rot.
Leaf blightMadroneDiseaseMadrone trees suffer from numerous fungal leaf diseases. One such problem, madrone leaf blight, appears to be caused by a pathogen that damages leaves after periods of cold weather in winter or early spring. Affected leaves develop brown spots which coalesce and form large blotches. The damage is worse where water collects (on the tips and edges of leaves and in the lower part of the canopy). Heavily-infected leaves may turn completely brown, sometimes throughout the entire canopy. Damaged leaves usually remain on the branches for several months, finally dropping off at the end of the following summer. New leaves emerging in the spring typically do not show symptoms of leaf blight. Young or stressed trees may be more severely affected than mature, healthy trees. Little is currently known about the long-term effects of this blight, though repeated loss of leaves will likely affect plant vigor and survival. Leaf blight on madrone should not be confused with other fungal leaf spot problems, which typically cause only minor damage. See also Madrone: Leaf spot.
Leaf gallMadroneDiseaseLeaf gall in madrone is caused by a fungus that infects leaf tissue. From late spring to mid-summer, fruiting bodies emerge from the leaf tissue, rupture the cuticle, and release their spores. Leaves become enlarged, discolored, and may exhibit a white, velvety appearance on one side. Spores in turn germinate on wet surfaces and may cause new infections of young, late-developing stems and leaves.
Leaf spotMadroneDiseaseMadrone leaf spot is caused by a fungus that can overwinter on the leaves. More than 18 species of fungi have been reported to cause leaf spots on madrone. The spots are about 1/4 to 1/2 inch in diameter and appear circular or irregular with grayish centers and purplish brown margins. Small black dots, the fruiting bodies of the fungus, may be seen in the center of the spots. On the lower leaf surface, the spots are light brown with darker brown margins. Sometimes the entire leaf surface may turn brown in response to infection by certain leaf spotting fungi. The fungal infection may result in defoliation. The disease is common in western Washington, but is only a problem some years. See also Madrone: Leaf blight.
Madrone cankerMadroneDiseaseSeveral different fungi can cause canker; they are spread by wind, rain, soil, tools, and equipment. They infect the tree at a wound and kill nearby healthy tissue. Cankers expand through the wood in all directions, and tree sap or dark fluid may ooze from the wound. Cankers eventually cut off nutrient and water flow to branches. Leaves may appear stunted or light green. These sunken, brown water-soaked cankers can appear on branches or trunk. Trees may cease spreading the disease by producing callus tissue to trap the fungus. If the expanding canker is controlled early enough, the tree usually survives. However, the fungus may grow faster than the callus, or the tree may not respond with a callus, resulting in serious damage.
Madrone leafminerMadroneInsectLarvae of this leaf and twig mining moth blaze sinuous, serpentine mines across the upper sides of leaves. Since leafminers usually cause only minor damage, they do not affect the long-term health of the tree.
Shield bearerMadroneInsectShield bearers are moth larvae that mine out elliptical pupal chambers on the leaves. When pupal cells drop off, "shot holes" or small "windows" are observed on the leaves. Shield bearers usually cause only minor damage.