1899. j PUBLIC DOCUMENT — No. 33. 147 



Another disease of the stone fruits, the so-called "plum 

 pockets" (^Exoascus Pnini, Fckl.), which causes young 

 plants to become swollen and distorted in a peculiar manner, 

 has been received several times this year. Besides the plum 

 (^Prunus domestica) , the wild cherry (^Prunus Yirginiana) 

 is also affected by the same fungus. The disease is not often 

 very abundant, but occasionally causes a considerable diminu- 

 tion of the crop. 



For methods of controlling the various diseases of the 

 peach, plum and cherry, consult the spraying ])ulletin annu- 

 ally issued by the horticultural division of this station. 



A 3Iii,sJc- melon Disease. 



During the latter part of August our attention was called 

 to a field of musk-melons, in which a destructive disease of 

 the leaves had api)eared and seemed to ])e rapidly increasing. 

 The owner informed us that he had lost his entire crop the 

 year before in the same way. It was evident that the trouble 

 began in the centre of the hills. Here the leaves at the time 

 of our first visit had in many hills wilted and begun to turn 

 yellow and partially died. They were covered with yellow 

 spots, or, in the worst cases, ^\'ith dead areas of considerable 

 size. At this time the general appearance of the field was 

 good, the only very noticeably afi'ccted places being these 

 centres of some of the hills. Still, it could be seen on closer 

 examination that scarcely a leaf in the whole field was entirely 

 healthy. On ahnost every one there were small yellow 

 spots, more or less abundant, some were slightly wilted, and 

 it was evident enough that the disease was spreading in each 

 hill from the centre outward. The dead areas on the most 

 aftected leaves were dry and l)rittlc, marked with slight con- 

 centric rings, and a dark, mould-like growth could be seen 

 upon them. Examined with the microscope, this proved to 

 be a fungus, and a species of Alleniaria. It grew abun- 

 dantly in the tissue of the leaf as well as upon the surface, 

 where the dark-brown, club-shaped spores were produced. 

 No other fungus or other organism could 1h^ found on the 

 aftected leaves, and there seemed but little doubt that this 

 was the direct cause of the trouble. Furthermore, Dr. W. 



