408 Pflanzenkrankheiten. 



pyrethre et des autres agents tres efficaces quand ils sont appliques 

 dans des circonstances opportunes. P. Vuillemin. 



Mc Rea, W., Rows of Spots on the Leaves of Palmyra Palms. 

 (Agric. Journ. India VII. 3. p. 272-279. 5 pl. July 19120 



A leaf-disease caused by the bud-rot fungus Pythium palmivo- 

 ruin Butler is described. In "bud-rot" the growing-point is killed 

 owing to the fungus atlacking the palm below the level of the crown. 

 The "leaf-spot" disease is brought about wlien infection takes plaee 

 above the level of the growing point, the fungus attacking the leaf- 

 sheaths over the growing apex and the folded leaves within. In some 

 cases the leaves die; in others they expand normally, but are mar- 

 ked with concentric rows of spots. At times the fungus grows down- 

 wards and infects the crown. A. D. Cotton. 



Metealf, K. and J. F. Collins. The control of the Chestnut 

 bark disease. (U. S. Dept. Ag. Farmer's Bul. 467. p. 1-24. 1911.) 



This buUetin contains a brief discussion of the history and 

 distribution of the disease in question, citing among other points 

 the tinancial losses, cause of the disease and Symptome, dissemi- 

 nation and means of entrance into the host plant. The control of 

 the disease by elimination and quarantine is treated in a suggestive 

 manner. Considerable detail is included in the treatment of melhods 

 of locating advance infections, in the destruction of such infections, 

 in developing an "immune zone", and in quarantine possibilities. 

 An extract is given of the Pennsylvania law relating to this 

 disease. Suggestions are included as to the inspection of diseased 

 nursery stock, the individual treatment of diseased trees, and advice 

 is offered to chestnut orchardists, to owners of chestnut woodland, 

 as well as to owaers of ornamental chestnut trees. Tlie financial 

 loss at the time was estamined at $ 25,000,000. R. J. Pool. 



Ravaz et Verge. Les conditions de developpement du 

 mildiou de la vigne. — Recherches experimentales. (1 

 vol. 8'\ 61 pp. 9 flg. Montpellier, Coulet. 19i2.) 



Les spores de Piasmoparn viticola tombent sur la face supe- 

 rieure des feuilles. Si elles n'y sont pas tuees par les fongicides, 

 elles eraettent des zoospores dans l'eau; ces zoospores gagnent la 

 face inferieur si la couche liquide s'etend jusqu'ä cette face. Les 

 tubes germinatifs s'introduisent dans la feuille par la face inferieure; 

 l'invasion debute par la peripherie. 



La germination n'est possible que dans certaines limites de 

 temperature; les conidies resistent ä la congelation, non ä la cha- 

 leur; elles ne germent que dans l'eau et perdent leur faculte ger- 

 minative en 5 jours dans l'air meme tres humide. Les feuilles ne 

 sont pas contaminees ä une temperature inferieure ä 13°; c'est vers 

 2QP que le mildiou apparait le plus vite; il fant de plus une humi- 

 dite persistante. Outre l'humidite de l'air le Plasmopara exige üb 

 Support tres aqueux. Une vigne est d'autant plus receptive que la 

 tension osmotique du suc cellulaire est moins elevee. Cette condition 

 peut 6tre modifiee par le greffage. En general le mildiou est favo- 

 rise par les porte-greffe de la serie nipestris, entrave par ceux de 



