or almost black or the Invasion may produce only small dark colored streaks in 

 the heartv/ood. The fungus progressively enters the sapwood and finally kills 

 the branch, or if it has entered the trunk, kills the tree. If a section of 

 branch v;ith discolored heartwood, where the fungus is present, is set in water 

 and enclosed to provide a humid atmosphere around the branch, the brown dis- 

 coloration diffuses from the heartwood into the water and the fungus grows out 

 on the surface of the branch as a white cottony mold. 



The fruiting bodies of the fungus may appear before or after the branch 

 or tree dies or may not appear at all. They develop on dead parts of the trunk 

 and branches and are extremely variable in size and form. They may be 1/4, 1/2, 

 or 1 inch in diameter, circular or elongated. They may lie flat on the upper 

 surface of the branch with reflexed margins or may project, overlapping and 

 shelf-like, from the sides, or may be flat against the underside of a branch. 

 The upper surface of the brackets is usually hairy and grayish or buff in color. 

 The under surface, V7hich is the fruiting layer, is smooth and purplish when 

 young or may have tinges of light blue or rose. It turns dingy with age. Tre- 

 mendous quantities of spores are produced from the fruiting surface of the fruit- 

 ing bodies. 



I^JFECTIOH 



Stereum purpureum spores land on, germinate and enter through dead wood 

 produced by winter injury, declining vigor such as caused by "v/et feet" or 

 mouse injury, sunscald, and pruning v/ounds, particularly dead stubs where side 

 branches have not been cut close or where branches have been "headed back". 

 It first attacks the heartvrood, then the sapwood, and finally the bark. 



COI^rrilOL 



Good cultural practices help keep damage to a minimum. There is no effective 

 chemical treatment. The following practices are suggested; 



1, Keep trees in good grovjing condition. It gives trees a chance 

 to resist the disease and often infected trees vjill survive. 



2, Remove all branches in the tree that are dead or have fruiting 

 bodies on them. If fruiting bodies are on the trunk, even 

 though part of the tree may be alive, remove the entire tree. 



3, Remove all branches showing silvered foliage beyond the point 

 showing brown discoloration in the heartwood . If the brown dis- 

 coloration extends into the trunk, remove the tree. 



4, It is a good practice to burn all dead wood and prunings in an 

 orchard because not only the silver leaf fungus but other rots 

 continue to live on dead wood. 



5, Make pruning cuts close so that there are no stubs which may die 

 back later and provide a place for infection. Remove all dead 

 stubs when found, making cuts in live vigorous tissue so they 

 have a chance to heal over. 



