Diseases of plants induced by Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae diseasesofplant00tube Year: 1897 164 AKCOJIYCKTKS. may bear several brooms, and every tree in a fruit-gaiden 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 hotanical magazine, 1895) witclies' brooms are produced in Japan on Prunus pseudo-cei', by a distinc
Diseases of plants induced by Diseases of plants induced by cryptogamic parasites; introduction to the study of pathogenic Fungi, slime-Fungi, bacteria, & Algae diseasesofplant00tube Year: 1897 164 AKCOJIYCKTKS. may bear several brooms, and every tree in a fruit-gaiden 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 hotanical magazine, 1895) witclies' brooms are produced in Japan on Prunus pseudo-cei', by a distinct species, Ex. j-iscufhi- crrasiis.] Exoascus minor Sad. This species induces hypertrophy of shoots of Prunus (cera>> and P. Cerasi's, but cannot be said to cause formation of witches' brooms. The m'celiuni hibernates in the buds, and spreads only underneath the cuticle, while that of Kr. 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 Fig. 5i».—Twig from witches' broom in bc attacked, whilc their ncigll- foliage, as in Fig. 57. Photographed at same ' . • i i i time as Fig. .58 for compaiison. (v. Tubeuf l3ours remain quitc healthy; both flowers and fruit may also be borne. Diseased leaves appear much crumpled, and Sadebeck states they have an odour of cumarin ; they turn brown pre- maturely and fall off. Exoascus insititiae Sad. is found on Prunus domestica and P. in Europe, and P. pennsylvanica in Xorth 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 Ex. 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 curled up, and fall off early. To prune off' all brooms is the best preventive
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