Aspen Bibliography

Studies on the Ink-Spot Disease of Poplar

R. Pomerleau

Document Type

Article

Journal/Book Title/Conference

Canad. J. Res. [Department of Lands & Forests, quebec.]

Volume

18

Issue

Sec. C

First Page

199

Last Page

214

Publication Date

1940

Abstract

A foliage disease of poplar caused by Sclerotinia bifrons (E. & E.) Whetzel has been studied during an important outbreak in the years 1935–1937. The perfect stage of this fungus has been correctly named by Whetzel. The fungus hibernates on the ground in the sclerotial condition, and during the spring apothecia are produced on sclerotia. Inoculation of the leaves is induced by ascospores ejected from apothecia. After two or three weeks of incubation, reddish areas appear on leaves; new sclerotia are formed in the lesions in June and are ready to fall about July 15. The epiphytotic development of the disease is favoured by the following set of conditions: presence of a fairly large number of sclerotia on the ground, occurrence of a dense stand of young poplars, low temperature and high humidity before and at the time of foliation. Quite a number of trees at the sapling stage are killed and others are affected by an intense defoliation, during an outbreak. These effects are noticeable only in thickets of pure population of Aspen, which represent usually the first stage of natural reforestation under Quebec conditions.

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