PLUM DISEASES. 127 



tacked by what is called the "Gumming Disease." Its 

 presence is indicated by globidar masses of colom'less gum 

 oozing out of the bark of the trunk and branches. These 

 masses are usually of a soft texture in damp weather and 

 hard in dry weather. It appears that this disease is the 

 result of a. fungus gaining an entrance to the tissues by 

 means of wounds in the bark, or such as would be formed 

 by pruning. When badl_y attacked the branch often dies 

 or becomes very unhealthy. 



Kemedies. — In the case of a bad attack the only course 

 is to burn the tree. Where only slightly attacked cut 

 away the diseased parts and paint the wounds with Stock- 

 holm tar. Mr. George Massee recommends that the soil 

 around the tree be dressed with quicklime to destroy the 

 conidia stage of the fungus, which has been washed down 

 from the gum masses by rain. 



Plum-Leaf Blister (Polystigma rubrum).— A fun- 

 goid disease which attacks the under sides of plum leaves, 

 forming reddish patches studded with dark dots. If very 

 prevalent it arrests the development of leaves and fruit. 



Remedy. — Collect and burn the fallen leaves in autumn. 



Silver-Leaf Disease (Stereum purpureum). — A 

 modern disease which has attacked the foliage of plums, 

 cherries, peaches, and Portugal laurels very seriously 

 during the last few years. As yet its life history is not 

 fully understood. It cauises the leaves to assume a 

 silvery hue on their upper surface and a yellowish tint 

 underneath. In a recent report of the Woburn Experi- 

 mental Fruit Farms it is stated that trees could be inocu- 

 lated at any time from January to July with minute par- 

 ticles of the fungus, in root, stem, or branch, but most 

 effectively in stem. Other experiments showed that the 

 disease is not spread from affected to healthy trees by the 

 operations of pruning or cultivation, as it does not run 

 from one tree to its immediate neighbour, nor does it 

 spread in the direction in which it would have been car- 



