. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 164 ASCOMYCETES. may bear several brooms, and every tree in a fruit-garden may be attacked, so that this disease has assumed consider- able economic importance. As a preventive measure, the removal of all brooms at the time of pruning the trees is strongly recommended. [According to Shirai {Tokio botanical ma<jazinc, 18 9 5) witches' brooms are produced in Japan on Prunvs j^seudo-cerasics, b
. Diseases of plants induced by cryptogamuc parasites; introduction to the study of pathogenic fungi, slime-fungi, bacteria, and algae. English ed. by William G. Smith. Plant diseases; Parasitic plants. 164 ASCOMYCETES. may bear several brooms, and every tree in a fruit-garden may be attacked, so that this disease has assumed consider- able economic importance. As a preventive measure, the removal of all brooms at the time of pruning the trees is strongly recommended. [According to Shirai {Tokio botanical ma<jazinc, 18 9 5) witches' brooms are produced in Japan on Prunvs j^seudo-cerasics, by a distinct species, Ux. ^we^^r/o- ccrafivs.] Exoascus minor Sad. This species induces hypertrophy of shoots of Prv/iius ChamatceraHus and P. Cerasus, but cannot be said to cause formation of witches' brooms. The mycelium hibernates in the buds, and spreads only underneath the cuticle, while that of Ux. cerasi lives in the tissue of the twigs and leaves. It is characteristic of this species that only leaves here and there on a twig may be attacked, while their neigh- bours remain quite healthy; botli Howers and fruit may also he borne. Diseased leaves appear much crumpled, and Sadebeck states they have an odour of cumarin ; they turn brown pre- maturely and fall oft. - Exoascus insititiae Sad. is found on Prunvs domestica and P. Insititia in Europe, and P. -pcnnsylvanica in North America. It causes formation of witches' brooms smaller than those on the cherry tree, yet probably more common in the fruit garden. They bear no fruit, and are a source of considerable loss. The mycelium hibernates, like that of E,r. cerasi, in the bark of twigs, and spreads in spring into the buds. The leaves of the host bear asci on the lower epidermis; they are always more or less cuiled up, and fall off early. To prune off all brooms is the best preventive Fig. 59.—Twig from witches' broom in foliage, as in Fig. 67. Photographed at same time as Fig. 58 for comparison, (v. Tubeuf phot.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectparasit, bookyear1897
