Diseases of deciduous forest trees Diseases of deciduous forest trees diseasesofdecidu149vons Year: 1909 DISEASES CAUSED BY WOUND FUNGI. 41 SOFT ROT OF OAKS CAUSED BY POLYPOKUS OBTUSUS. A number of species of the black oaks, notably Qucrcus marilandica Muench. and Q. velutina Lam., are affected with a disease of the heart- wood which has been determined by Spaulding (94) to be due to Poly- porus obtusus Berk. Diseased trees have been found in the eastern part of the United States, and notably in the central Mississippi Val- lev; a large number of trees are usually found affected in a localit
Diseases of deciduous forest trees Diseases of deciduous forest trees diseasesofdecidu149vons Year: 1909 DISEASES CAUSED BY WOUND FUNGI. 41 SOFT ROT OF OAKS CAUSED BY POLYPOKUS OBTUSUS. A number of species of the black oaks, notably Qucrcus marilandica Muench. and Q. velutina Lam., are affected with a disease of the heart- wood which has been determined by Spaulding (94) to be due to Poly- porus obtusus Berk. Diseased trees have been found in the eastern part of the United States, and notably in the central Mississippi Val- lev; a large number of trees are usually found affected in a locality. The spores of the fungus germinate in the burrows of an oak-boring insect {Prionoxystus robiniae Peck.). The fungus grows in the borings and follows the in- sect burrow until it reaches the heart wood of the tree; it then spreads out from this point, both up and down the trunk, and gradually brings about a form of soft rot. () The dis- eased wood is lighter in color than the heart wood of the healthy tree, and in its lasl stages turns almost white. 'The diseased wood retains its-fibrous appearance, but breaks much eas- ier than does the healthy wood. It does not have the shrinkage cracks which are so charac- teristic of some of the wood rots; neither does the affected tissue crumble between the fingers nor break very easily into small flakes ' (94). The fungus grows in the trees rapidly, extending up and down in the heart wood and growing outward until it reaches the sap wood. Affected trees are weakened to such an extent within one or two years after their first attack that the slightest windstorm causes the trunks to break. The sporophore of Polyporus obtusus is a very characteristic one. It usually appears at the original insect burrow, where it forms a thick, more or less hoof shaped shelf; in some cases two or three shelves may form, one immediately above the other. The sporo- 149 Fig. 5.—A living black oak tree with a sporophore of Polyporus obtusus growing
Size: 1245px × 1606px
Photo credit: © Bookend / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
