APPLE LEAF-SPOT CAUSED BY SPHAEROPSIS MALORUM. 49 



leaf-spots or Phyllostictae fungi, but are apt to be more irregular 

 and larger*" The same author, 9 in 1903, stated that most of the apple 

 leaf-spot troubles in Connecticut were due to this same fungus. 



Stone and Smith, 10 1903, in accounting for a serious outbreak 

 which occurred in Massachusetts the previous year say " there can 

 be no reasonable doubt that frost was the destructive agency." They 

 observed that the spotting of the leaves continued throughout the 

 summer, and that even as late as August spots as a result of spring 

 frost developed on leaves which had not previously shown the injury. 



Sheldon, 11 in 1907, transferred the fungus Phyllosticta pirina Sacc. 

 to the genus Coniothyrium on account of the dark color of the spores 

 and proposed the name Coniothyrium pirina (Sacc.) Sheldon. From 

 an examination of herbarium material and fresh specimens from dif- 

 ferent parts of the eastern United States there is no doubt that the 

 fungus commonly called Phyllosticta pirina in this country is a Coni- 

 othyrium. Apparently mature spores from a European specimen of 

 Phyllosticta pirina in the herbarium of the Department of Agricul- 

 ture are hyaline and ellipsoid, agreeing with the original description 

 of Saccardo, 12 so that his species may prove to be autonomous. 



In view of the conflicting statements and apparent uncertainty as 

 to the cause of apple leaf -spot, the writers during the summer of 

 1906 and 1907 made a study of the disease in connection with demon- 

 stration spraying work in the Ozarks. It was found that Sphaerop- 

 sis malorum, contrary to the general belief, is the cause of the disease. 



CULTURAL STUDIES. 



A somewhat cursory examination of a large amount of leaf -spot 

 material collected in Arkansas during 1906 showed that there was no 

 one fungus which fruited constantly on the spots. The pycnidia of 

 Coniothyrium pirina (Sacc.) Sheldon were found perhaps more 

 commonly than any other, but two species of Pestalozzia and one 

 each of Coryneum, Hendersonia, and Alternaria occurred frequently, 

 while occasionally the pycnidia of Sphaeropsis malorum and a spe- 

 cies of Septoria were met with. The same was true of specimens 

 received from Missouri, Nebraska, New York, Maryland, Virginia, 

 and West Virginia. Pure cultures of all of these fungi were easily 

 obtained by the poured-plate method. All grew well and fruited 

 abundantly on apple agar or sterilized apple wood. 



In the early part of the season of 1907 cultures were obtained from 

 leaf spots by a somewhat different method. During the first spring 

 outbreak of the disease, spots of various sizes, together with a little 

 of the surrounding healthy tissue, were cut from the leaf and placed 

 in a solution of mercuric chlorid (1-1,000) for two or three minutes. 

 The bits of leaf were then thoroughly washed in sterile water and 



121— v 



