abstracts: phytopathology 565 



manure or stable manure not thoroughly decomposed, and in which 

 the organisms of decomposition are still active. If conditions are 

 such that the plants are kept growing vigorously, these organisms will 

 have no effect upon them, but if bad weather conditions obtain and the 

 lettuce plants get weakened or growth is retarded, these organisms 

 make their way into the roots or leaves and cause disease. The treat- 

 ment recommended is the use of thoroughly decomposed green manure 

 and well-seasoned stable manure in which tissue-disintegrating bacteria 

 are inactive. 



The Kansas disease is caused by a soil organism, to which the name 

 Bacterium marginale has been given. It produces either a marginal 

 wilting, or a spotting and speckling of the leaves. Care in watering 

 plants so that soil does not get washed on the leaves and proper ven- 

 tilation of greenhouses will prevent the disease. 



Isolations, inoculations, cultural characteristics, and descriptions of 

 the two organisms are discussed. N. A. B. 



PHYTOPATHOLOGY. — Influence of te?nperature and precipitation on 

 the blackleg of the potato. J. Rosenbaum and G. B. Ramsey. 

 Journ. Agr. Res. 13: 507-513, fig. 1, tab. 3. June 3, 1918. 



Experiments were performed which showed that the organism 

 (Bacillus phytophthorus Appel) producing the blackleg disease of the 

 potato, under the winter conditions that existed during 1915-1916 

 and 1916-1917 in Aroostook County, Me., cannot live over in the soil 

 or in diseased tubers that may remain there. 



Comparison of weather records show that the winter of 1915-1916. 

 was not an unusual one for Aroostook County. 



The severity of the disease during the growing season is closely corre- 

 lated with temperature and precipitation. A high temperature and 

 low precipitation tend to diminish the disease, while a low temperature 

 and high precipitation produce conditions favorable for it. J. R. 



PHYTOPATHOLOGY.— yl hitherto unreported disease of okra. L. L. 



Harter. Journ. Agr. Res. 14: 207-211, pi. 23, figs. 3. July 



29, 1918. 



The author investigated a disease of the pods and stems of okra 



which occurred in Maryland in 1916. Infection experiments showed 



that several different varieties of okra were susceptible. The causal 



fungus was described as a new species of Ascochyta, A. abelmoschi. 



L. L. H. 



