File:Bulletins on forest pathology - from Bulletin U.S.D.A., Washington, D.C., 1913-1925 (1913) (19883916363).jpg

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. was marked "infected." Four trees specifically studied yielded by actual count an average of 220 burls on the branches and 13 on the trunks. The cones produced by these trees, although of average number, were small, with a higher percentage of abortive sporophylls than is commonly the case with this species (fig. 3). Comparative germination tests of seeds from heavily infected and vigorous non- infected jack pine of the same age and type conditions showed for the former a germination of 19 per cent below that of the latter. For this experiment 10 samples, consisting of a dozen or more cones, were taken from each of five heavily infected and five uninfected pines. Fifty seeds from each of these samples were plant- ed in sand, kept moist with distilled water, and allowed to stand at labora- tory temperature (about 70° F.) for 90 days. The prolific devel- opment of Periderm- ium cerebrum in many parts of the jack-pine forests of the Great Lakes region is a factor in reforestation which should be carefully considered. The fact that the fungus occurs so commonly on young seedlings in the natural forest and occasionally in the nursery shows that it is a menace to the best development of the species. The largest and best formed jack pine in all the regions studied where the Peridermium was abundant was almost entirely devoid of this injurious disease. However this may be interpreted as to the original differences in vigor, the fact that heavily infected trees were invariably scrubby and ill formed is, in the mind of the writer, directly referable to the effects of the parasite. The fact that P. cerebrum has its telial stage on the leaves of several
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Fig. 3.—Branch of jack pine with aborted cones, the result of a severe attack of Peridermium cerebrum. Note that some of the cones did not open and that most of them are less than an inch in length. Average normal cones measure from 1J to 2 inches.

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