190 MAINE AGRICULTURAL EXPERIMENT STATION. 1916. 



Observations made last summer indicate that in all probability 

 silver leaf is as common on apple trees in Maine as it is in the 

 adjoining portions of Canada. On account of its frequently 

 inconspicuous appearance, and partially from a lack of 

 familiarity with the characteristic symptoms of the disease, on 

 the part of those who are interested in matters of this kind, 

 it has not been recognized previously. 



The writer's attention was first called to this abnormal con- 

 dition of apple foliage by Dr. L,. R. Jones of Wisconsin during 

 a visit of the latter to Maine in the summer of 1915. Doctor 

 Jones stated that he had previously had opportunity to observe 

 the trouble in company with Professor Giissow. It was at once 

 evident that the true "silver leaf," as it occurs in Maine, is a 

 much less conspicuous trouble than certain cases reported from 

 Canada. Nothing has yet been seen which would conform to 

 the following sentence. "Some of the trees are so silvery in 

 appearance that their abnormal condition is apparent from a 

 great distance." 



Instead of being silvery the diseased foliage had a distinct, 

 dull, leaden, metallic luster. The name "plomb" used to desig- 

 nate the disease by the French seems more applicable to the 

 cases observed in Maine. While trees showing this condition 

 may be overlooked by the average individual, the abnormal ap- 

 pearance of the affected leaves is sufficiently marked so that 

 they are readily detected a short distance away by anyone who 

 has become familiar with the characteristic symptoms. When 

 the diseased and healthy leaves are placed side by side the dif- 

 ferences are apparent to any observer. 



The writer was unable to collect any confirmatory evidence 

 last season relative to 5. purpureum being the cause of the dis- 

 ease. It was observed that every tree or branch which showed 

 silver leaf also presented some slight evidence of winter injury 

 resulting from the season immediately preceding. This fact 

 was quite evident at Highmoor Farm where practically all of the 

 cases were confined to one or more limbs on an affected tree, 

 but never involving the whole tree. S. purpureum was not 

 observed on any of these trees, but it follows winter injury of 

 apple trees in Maine with great regularity. 



