Mushroom Root Rot
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Importance. - Mushroom root rot causes losses in more than 200 plant species in the Southern United States from Oklahoma eastward. Ash trees are more commonly attacked when growing slowly and already weakened by wounding or defoliation. Identifying the Disease. - Leaves turn yellow, become sparse or are undersized, and drop prematurely. Roots may be partially decayed or completely girdled at the root collar. Basal lesions may extend up to 30 cm or more above the soil line. Affected trees show general loss of vigor and dieback and have increased susceptibility to windthrow. Identifying the Fungus. - Clusters of yellow mushrooms develop at the base of infected trees from June through October, usually associated with summer rain and moist soil. Mushrooms produce white basidiospores. The root collar must be excavated for diagnosis if mushrooms are not present. White to tan mycelial mats form under the bark. Narrow, black mycelial strands (rhizomorphs) occasionally develop in bark fissures or under dead bark above mycelial mats on the root surface. |
Fruiting Bodies; Clytocybe lucidum on oak |
Fruiting Bodies |
Biology. - The fungus can persist in dead or dying root tissues for many years. The rhizomorphs spread through the soil, attach to roots, and produce hyphae that penetrate healthy tree roots. Infected roots gradually die, resulting in decline and mortality of the tree. Mushrooms may be produced when large roots or the stem dies.
Control. - Cultural practices that reduce tree stress should be used. Mortality can be minimized by regular fertilization and irrigation. Infected trees and roots should be removed from the soil before replanting.
