Which disease is associated with white mycelium under the bark, black rhizomorphs, and honey-colored mushrooms?

• A. Armillaria
• B. Laminated root rot
• C. Black stain root disease
• D. Dwarf mistletoe

Answer: (A)

Armillaria, known as honey fungus, is identified by a distinctive combination of signs: white, fan-like mycelium under the bark indicating active colonization of the cambium, black rhizomorphs (shoestring-like cords) spreading through roots and soil, and honey-colored mushrooms that appear at the base of infected trees or on stumps. The white under-bark mycelium shows the fungus is feeding on the tree, the black rhizomorphs enable spread to nearby hosts, and the honey mushrooms are the fruiting bodies that release spores to continue infection. In contrast, laminated root rot typically shows laminated, crusty decay and conks rather than white under-bark mycelium or honey-colored fruiting bodies, black stain root disease involves dark staining in sapwood without the rugose rhizomorphs or mushrooms, and dwarf mistletoe is a parasitic plant signaled by witches’ brooms and needle loss rather than these fungal features.