Title: (Bulletins on forest pathology : from Bulletin U.S.D.A., Washington, D.C., 1913-1925)
Identifier: bulletinsonfores00unit (find matches)
Year: 1913 (1910s)
Authors: United States. Dept. of Agriculture
Subjects: Trees; Plant diseases
Publisher: (Washington : U. S. Dept. of Agriculture)
Contributing Library: Robarts - University of Toronto
Digitizing Sponsor: University of Toronto

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PATHOLOGY OF THE JACK PINE. brain—cerebroid. These blisterlike swellings are orange-yellow at first; after the rupture of the peridium and the dispersal of the golden yellow seciospores they become whitish. The gall formation causes great injury to the trunk and branches (fig. 1). The infection usually begins by means of some injury to the bark or cambial layer.1 The gall swellings gradually increase from year to year from the growth of a perennial mycelium, so that they finally encompass the entire branch, resulting eventually, if the galls are near the trunk, in its death below and above the hypertro- phy. Whether or not the entire branch dies depends upon the presence of lat- eral, leafed branches below the gall. In dry sandy areas Peridermium cere- brum confines itself more generally to the branches, occurring rarely on the trunk but frequently in the axils of the branches. This latter condition usually results in a combination trunk and branch gall, which in numerous instances produces greater damage than either of the other two types of galls. The branch and trunk are girdled by abnormal wood tissue and are thus weakened (fig. 2). This results usually in either the branch or the tree being blown down by the wind. Personal observations show that borers and wood-rotting fungi entering at the burl often hasten the decline of the tree. From a careful examination of young twigs showing very recent infections at leaf scales, leaf traces, and at the bases of young pistillate
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Fig. 2.—Cross sections of the main trunk of a jack pine heavily in- fected with Peridermium cerebrum. Note the progressive girdling by the resinous burl tissues in the upper figure and its effects on the increment of the trunk below, as shown in the lower figure. 1 Wounds made by sapsuckers, ovipositors of bark-stinging insects, rodents, and ice and snow breaks are common means of entrance for Peridermium cerebrum.

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