868 



AN^ ACCOUNT OF 80ME OBSERVATIONS UPON THE 

 LIFE-HISTORY OF FHOMA CITRICARPA McAlp., 



The Cause of the ''Black Spot" Disease in Citrus Fruit in 

 New South Wales. 



By G. p. Darnell-Smith, D.Sc, F.I.C. 



(Plates Ixxxiv.-xc.) 



Historical. 



A. H. Benson (1) briefly described the symptoms of a disease, 

 to which he gave the name of the Black Spot disease of the 

 Orange, in 1895. He stated that it was probable that it was 

 identical with a disease of the orange in Europe, that had been 

 alluded to by Sorauer, under the name of "Schwartz" or black 

 disease of the orange. There is little doubt, however, from his 

 figure, that it was the disease caused by Phoma citricarpa 

 McAlp., with which Benson was dealing. Benson records the 

 disease as occurring at Seven Hills, Castle Hill, Dural, the 

 Kurrajong, and Emu Plains. 



N. A. Cobb (2) described the Black Spot Disease of the orange 

 in 1897. He gave some excellent figures of affected fruit. He 

 also figured the spores. According to Cobb, "these spores arise 

 after the manner of those of the genus Glceosporium. It is pos- 

 sible, therefore, that the Australian form is the C olletotriclmm 

 adustum of Ellis." He further stated that the spores were borne 

 in large numbers in tandem-fashion from the mycelium at the 

 base of the interior of the pycnidium in a manner entirely similar 

 to those of the Bitter Rot of the apple, and gave the size of 

 spores as 7-8 x 10-15/x. 



The fungus causing the Black Spot Disease of Citrus fruit was 

 described as a new species under the name of Phoma citricarpa 

 by D. McAlpine, in " The Fungus Diseases of Citrus Trees in 



