336 FUNGOUS DISEASES OF PLANTS 



XXXVI. MARSONIA 



Marsonia Populi (Lib.) Sacc. 1 is a common leaf spot or anthrac- 

 nose of many species of poplar (Populus) in Europe and America. 

 It is more frequently seen upon the white poplar {Populus alba). 

 It is often a destructive fungus in the nursery. It may also appear 

 as a twig blight. The young leaves may be killed and the fungus 

 may even extend to the main shoot and branches, or it may occur 

 upon the twigs in isolated black spots. When somewhat older, 

 nursery stock may show black spots at the older nodes, indicating, 

 apparently, infection through the leaves. 



Marsonia ochroleuca B. & C, causing a leaf spot of chestnut, is 

 a fungus which, while far less dangerous to the general growth of 

 the chestnut tree than the canker, is far more widely distributed, 

 and seems to occur wherever the chestnut is known. It is frequently 

 injurious to a noticeable extent. Klebahn 2 has demonstrated a 

 connection between one species of Marsonia, Marsonia Juglandis, 

 and Gnomonia leptostyla. 



XXXVII. PEACH BLIGHT 



Coryneum Beijerinckii Oudem. 



Smith, R. E. California Peach Blight. Cal. Agl. Exp. Sta. Built. 191 : 73- 

 100. Jigs. 1 -1 6. 1906. 



Habitat relations. It is somewhat difficult to determine the 

 extent of injury caused by this fungus, since references to a disease 

 produced by this or related fungi have not always been clearly dif- 

 ferentiated from other peach diseases. In recent years, however, 

 this disease has been studied in California, where it has been un- 

 usually prevalent, causing great destruction during 1905-1906. 

 The organism had become gradually very abundant, and the sea- 

 sons were favorable to its continued spread. In general, the effect 

 of the fungus is to kill the buds on the fruiting wood, to produce 

 spots on the green twigs, to retard the development of the leaves, 

 and to cause dropping of the fruit. Accompanying the activity of 

 this fungus is a notable gumming of the twigs from the dead spots, 

 this being particularly abundant during moist conditions. It will 



1 Halsted, B. D. Poplar Blight in the Nursery. N. J. Agl. Exp. Sta. Rept. 15 : 

 349-396. 1894. 



2 Klebahn, H. Centrbl. f. Bakt. u. Infekskr. 15 (2 Abt.) : 336. 1905. 



