348 MAINE AGRICULTURAL EXPERIMENT STATION. 191O. 



in this publication (p. 378) there is considerable reason to 

 believe that some form of the lime-sulphur sprays in proper 

 dilution may be of service on such varieties. Bulletin 135 of 

 the Illinois Station by Prof. Chas. S. Crandall, and Bulletin 

 287 of the New York (Geneva) Station by Prof. U. P. Hed- 

 rick, treat of bordeaux mixture and bordeaux injury in relation 

 to the apple in a very comprehensive and exhaustive manner, 

 and these publications are recommended to any who wish fur- 

 ther information on this subject. 



Leaf spot. Spotting of the leaves is closely associated with 

 the russeting of the fruit by spray. However, a study of this 

 trouble extending over several years and representing material 

 collected in many different parts of the State shows that leaf- 

 spot in Maine is by no means confined to that caused by the 

 use of sprays. In 1908 leaf-spot was exceedingly abundant on 

 unsprayed trees all over the State. As is stated elsewhere in 

 this bulletin (p. 359) various fungi were found in these spots 

 on leaves from sprayed and unsprayed trees, but of these 

 Sphaeropsis malorum Pk. was the only one which was capable 

 of causing the disease on inoculation from pure cultures. 



While in some instances the spots caused by sprays did not 

 appear quite identical with those caused by the fungus, these 

 differences were not constant enough to enable one to distin- 

 guish one from the other with any degree of accuracy. More- 

 over old spots made by sprays were usually attacked by fungi 

 so that it is only by knowing the history of the case and noting 

 the relative amount of spotting of leaves on sprayed and un- 

 sprayed trees under like conditions that one is able to judge 

 whether the spotting is caused by sprays or fungi. Fig. 240 

 illustrates spotting caused by spraying and Fig. 241 spotting 

 caused by Sphaeropsis malorum. 



The first indication of the formation of a leaf spot is the 

 appearance of minute specks on the leaves where the healthy 

 green has changed to a reddish or purplish color. Soon these 

 change to larger, dead, brown spots, usually quite sharply de- 

 fined against the adjoining green, though in severe cases of 

 spray injury the whole leaf begins to turn yellow and soon 

 drops off, resulting in many instances in partial defoliation. 

 As a rule the spots are round, or oval and quite regular, but 

 they may be of various shapes and sizes. 



