MAINE AGRICUI.TUEAI, EXPERIMENT STATION. IQIO. 39I 



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

 this bulletin (p. 401) various fungi were found in these spots 

 on leaves from sprayed and unsprayed trees, but of these 

 Sphacropsis malornm 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. 59 

 illustrates spotting caused by spraying and Fig. 60 spotting 

 caused by Sphaeropsis malornm. 



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. 



It has been claimed that lime-sulphur sprays do not cause 

 leaf-spot. The experiments already referred to (p. 388) which 

 were conducted by Mr. Bonus in 1910 with lime-sulphur and 

 similar substitutes for bordeaux mixture used with lead arsenate 

 as an insecticide, indicate that exceptions to this statement 

 may be expected when these sprays are tried on the more tender 

 varieties like the Ben Davis. 



Experiments conducted at Orono by the writers in 1908 and 

 1909 with self-boiled lime-sulphur in comparison with bordeaux 

 mixture on Milding, Fameuse and Mcintosh resulted in no in- 

 jury with either spray. Moreover published reports of spray- 

 ing apple trees in Arkansas, Oregon, Missouri, New York and 

 New Hampshire, with self-boiled, home-cooked and certain of 

 the commercial lime-sulphur sprays are agreed as to the absence 

 of spray injury from lime-sulphur. However, in our own ex- 



