NEW APPLE LEAF TROUBLES. 189 



stated that neither he nor Dr. Jones had seen any apple injury in 

 that state which closely resembled this. 



Silver Leap. 



As far as the writer has been able to learn the only refer- 

 ences to this disease in American literature are contained in the 

 writings of Giissow. In 1910 he recorded its presence in Nova 

 Scotia.* In giving the characters of the disease he mentioned 

 that the leaves on the affected branches have a silvery appear- 

 ance or a milky-white gloss, particularly on the upper surfaces. 

 The epidermis on the upper surfaces of the leaves is also very 

 brittle. In this paper he states that when a branch is attacked 

 it dies, as a rule, after one or two years and that a tree once 

 attacked by silver leaf will eventually succumb. In this paper 

 he mentions that some European writers consider the disease to 

 be physiological but says that it is remarkable that Stereum 

 purpureum Pers! is constantly associated with it. 



In a second papery he states that it is known by him to exist 

 from Nova Scotia to Vancouver Island and expresses his sur- 

 prise that none of it should be recorded across the border when 

 it is evident that so many cases exist in Canada. At this time 

 he reported that he had only observed the disease on apples 

 and plums in Canada, but mentions the fact that pears,- peaches, 

 cherries, currants and gooseberries are also attacked by silver 

 leaf. He cites experimental evidence of his own and others, 

 particularly in England, tending to connect the cause of the 

 disease with S. puYpureum. 



In still a third paperf he reports more fully on the disease, 

 giving the results of inoculation experiments which lead him to 

 conclude that it is caused by S. purpureum. Therefore, as a 

 'control measure he would advise the destruction by burning of 

 all diseased branches and fully diseased trees. Any dead apple 

 wood including stumps in the orchard which might serve as a 

 breeding place for the fungus, which he looks upon as a wound 

 parasite, should be burned. 



*Giissow, H. T. Silver leaf. Report Dominion Botanist, Dept. of 

 Agric. Canada, 1910. p. 268. 



tGiissow, H. T. A preliminary note on silver leaf disease of fruit 

 trees. Phytopathology 1:177-179. Dec. 1911. 



tGiissow, H. T. Der milchglanz der obstbaume. Ztschr. Pflan^enk- 

 rank. 22:385-401. 1912. 



