Corky Bark Disease

Diplodia tumefaciens

A fungus that forms large black woody galls and rough-bark on the trunks and branches of poplar species (Populus). These may be single or concrescent, wart-like, and more or less globose or oval.
Diplodia tumefaciens Diplodia tumefaciens gall on the trunk of a mature Quaking Aspen (Populus tremuloides) about 50 years old. Corky Bark Disease,Diplodia tumefaciens,Geotagged,Minnesota,Populus tremuloides,Quaking Aspen,United States,Winter,fungus,gall


Mycelium, proliferating in hypertrophied host tissue, inter- and intracellular; hyphae in the periderm are thick-walled, darkly pigmented, septate, and thicker with depth of penetration, 2-9(-15) μm in diameter; the walls and lumen of the cells are often impregnated with brown and violet pigment; the ramifying hyphae extending downward into the cortex are hyaline, uniform in thickness, and 9-15 μm in diameter; the hyphal tips are tortuous and closely branched.

Linear and flattened bands of stromata are well back of ramifying hyphae and fully occupy the phellogen; they are formed from vesiculose cells 15-34 μm in diameter and dark violaceous-brown hyphae; bands are continuous or broken, 10-50 μm wide and frequently thickened into wedge-like structures 50-500 μm in diameter; they become gradually ruptured by pycnidia. Successive new layers of stromata are developed well below existing pycnidia.

Pycnidial initials are formed from meristogenous hyphae immediately below existing stromata; pycnidial chambers are filled with gelatinous matrix. Pycnidia flattened, scattered, discrete, and usually protected by a thin stroma above. Pycnidial wall thin in the bottom of the pycnidium, darker and thicker upward. Mature pycnidia at first embedded in hypertrophied cork and outer cortex of bark in stems and branches, occasionally erumpent, colored very dark violet to black, papillate, usually irregular or subglobose in shape, membranaceous-carbonaceous, ostiolate, caespitose or solitary, with a distinct inner and outer wall. Pycnidia measure (120-) 250-450 (-650) μm in diameter; occasionally two confluent chambers developed with a common pycnidial wall; sporiferous layer irregular.

Pycnidiospores mucose, oblong, ellipsoid, mostly obtuse, frequently somewhat irregular in outline and inequilateral, and flattened, with a basal scar provided with a marginal frill; spores are hyaline to yellowish, (20-) 28-40 (-50) X (6-) 9-15 (-18) usually continuous, rarely 1- to 2-septate and unequally celled, contents granular; membrane thick, many-layered, hyaline, but occasionally light brown when old; germinating readily. Micropycnidiospores rare, borne in the same pycnidia, hyaline, cylindrical and subcylindrical, 6-12 X 2-3 μm.
The sporogenous cells are annellophores with annellations inconspicuous except under oil immersion; annellophores are hyaline, long filiform to short subulate, occasionally septate and branched, 10-40 X 1-7 μm.


Diplodia tumefaciens (Shear) Zalasky (1964)
Macrophoma tumefaciens Shear, Phytopathology 5: 183


Over much of the northern USA and Canada. Also Holland and Belgium.


On Populus balsamifera, P. grandidentata, P. tremula, P. tremuloides, P. balsamifera, and P. trichocarpa


By spores and pycnidia


Populus (aspen, poplar, cottonwood) species.


Some text fragments are auto parsed from Wikipedia.

TUMEFACIENS SHEAR AND HUBERT]. Canadian Journal of Botany. Volume 42 (1964), pp. 1049-1055.
SpeciesDiplodia tumefaciens