Cellular structure and function are altered, causing a number of alterations in roots, trunks, and crowns. Armillaria inhabited roots decay, reducing or preventing absorption and translocation of water and mineral elements from the soil to above-ground parts. Above-ground symptoms may not be evident in small trees or in trees where root systems are killed rapidly. However, a number of nonspecific symptoms may develop in stems and leaves of older trees, where root decline and death is slower, including reduction in shoot growth, stem dieback, yellowing of foliage, defoliation, and stress-induced reproduction. Visual evidence of Armillaria infection on trunks includes internal and external resinosis and heart rot.
Basidiocarps appear in late summer or early fall and persist for only two to three weeks.
Their black, shriveled remains can often be found several months later, however. Evading the fungus by delaying planting for several years on land previously occupied by oaks. Eradicating or reducing fungus populations by removing dead and dying trees during harvesting operations. Eradicating or reducing fungus populations by plowing up and burning stumps of Armillaria-infected trees before replanting site. Avoiding wounding residual stand during logging operations.