550 EXPERIMENT STATION EECORD, 



The method of infection of grape leaves by Plasmopara viticola, L. Ravaz 

 and G. Verge (Compt. Rend. Acad. Sci. [Paris], 153 (1911), No. 26, pp. 1502- 

 150J,; Prog. Agr. et Vit. (Ed. VEst-Centre) , 33 (1912), Nos. 1, pp. 6-10, figs. /// 

 Jf, pp. 99, 100). — ^The authors hold as a result of a study of the biology of P. 

 viticola, the cause of the downy mildew of grapes, that the principal infection 

 comes from spores that find lodgment on the upper surface of the leaves. The 

 zoospores have been found very motile, and in the case of heavy or prolonged 

 rain they would doubtless find their way to the lower sides of the leaves. The 

 authors claim that if the upper surfaces of the leaves are well covered with 

 fungicides the zoospores will be destroyed and little infection follow. 



Recent investigations on the development and treatment of downy mil- 

 dew of grapes, H. Faes (Rev. Vit., 36 (1911), Nos. 933, pp. J,89-493; 93-',, 

 pp. 517-524, figs. 4 ; 935, pp. 545-550). — A report is given of observntions on the 

 development of the grape downy mildew (Plasmopara viticola) and means for 

 its control. 



The author, as a result of his investigations, maintains that infection is 

 almost exclusively through the stomata which are located on the under side of 

 the leaf. Spores of the mildew were placed on both faces of many leaves rep- 

 resenting the leading varieties of grapes, and in almost every instance no 

 infection followed where they were placed upon the upper side of uninjured 

 leaves, while a considerable proportion of infections followed their application 

 to the under surface of the leaves, or to the upper surface when the leaves had 

 been injured by hail. 



The author claims that his experiments show the necessity of modifying the 

 usual method of spraying grapes for the control of downy mildew, and that the 

 fungicide should be directed upon the under sides of the leaves. 



The development of the disease on the fruits remains to be investigated. 



The simultaneous occurrence of downy mildew on June 30, 1911, in 

 several distant localities, J. Capus and M. Bailly (Rev. Vit., 36 (1911), No. 

 920, pp. 129-133). — The authors have investigiated the occurrence of the downy 

 mildew of grapes in its relation to atmospheric and other conditions in Bur- 

 gundy, Poitou, and about Bordeaux. In the 3 regions the meteorological con- 

 ditions between June S and 14 were essentially the same, and the downy mildew 

 made its appearance about June 30 in all 3 regions, indicating that the infection 

 is closely associated with atmospheric conditions of a general character. 



A study of roncet of the grape, R. Aveena-Sacca (Atti R. 1st. Incoragg. 

 Napoli, 6. ser., 62 (1910), pp. 113-1^3). — The author reports upon a study of 

 roncet or court noue of grapes, one of the striking characteristics of which is 

 the greatly shortened internodes. In addition the stems are weak and often 

 fasciated. The leaves ai'e commonly less developed, sometimes chlorotic, dried 

 along the margins, and the tips extended and often blackened. The fruit, if 

 any is produced, is abortive and deformed. 



A review is given of various theories that have been advanced as to the cause 

 of this disease. From his investigations the author is led to consider it a 

 functional disorder, characterized by a partial degeneration of the parenchyma- 

 tous tissues of the plant followed by the production of a mucilaginous substance 

 which is noninfectious when applied to sound plants. There appears to be a 

 connection between this disease and sudden changes in temperature during the 

 early spring. 



The disease may be distinguished from anthracnose and mal nero, both of 

 which it somewhat resembles in gross appearance, by the absence of the 

 pustules formed by the fungus Oloeosporium ampelophagum, the cause of 

 anthracnose, and by the infectious character of the gum in mal nero. 



