6 BULLETI17 1118, U. S. DEPARTMENT OF AGRICULTURE. 



Swingle and Webber {28, p. 20-24) were the first to conduct 

 extensive field studies and spraying experiments for the control of 

 scab. They attribute its cause to a species of Cladosporium and 

 state that so far as is known this fungus is found only on citrus plants 

 affected by this disease. A description of this fungus and spore and 

 hypha (sporophore ?) measurements are recorded, as well as the 

 varieties attacked and conditions under which infection takes place. 

 They consider that this disease was imdoubtedly introduced into 

 America on the Satsuma orange (budwood) from Japan. Copper 

 sprays were found effective against this disease. 



Massee {12, p. 310-311) attaches the specific name ^^ citri pro tem." 

 to the generic name Cladosporium, not for final acceptance but for 

 convenience in reference. He gives Swingle and Webber's measure- 

 ments of spores and sporophores and adds a brief description of their 

 form. Briosi and Farneti {1) describe the ruggine bianca of lemons 

 in Sicily and state this disease is caused by Ehynchodiplodia citri, 

 having several conidial forms, among them Cladosporium citri. This 

 organism differs but little from C. citri occurring in Japan and 

 America. - 



In order to correct the confusion between Oladosporium citri 

 Massee and C. citri Briosi and Farneti, Saccardo {18, p. 1366-1367) 

 gives to the latter species the name C. farnetianum and records the 

 former as C. citri Massee. 



In March, 1906, Fawcett {2) isolated a hitherto undescribed fungus 

 from sour-orange leaves. He made mention of certain of its cultural 

 characters and used the name Cladosporium citri in connection with 

 this new organism. In a later publication {3) he calls attention to 

 a series of errors which had crept into the literature in regard to the 

 confusion of C. elegans Penz. with C. citri pro tern. Massee. Still later 

 Fawcett (4) proved by a series of inoculations that the scab is caused 

 by the fimgus found by him in scab lesions as early as March, 1906. 

 The characters of this true citrus-scab organism were illustrated and 

 again described. Unfortunately this pathogen was left without a 

 name to distinguish it from the saprophytic organism illustrated by 

 Scribner {20) and described by Swingle and Webber {28, p. 20-24) 

 and by Massee {12, p. 310-311). The result is that two organisms, 

 very distinct in morphological and cultural characters (the one a true 

 parasite, the other a saprophyte) have been referred to in the literature 

 as Cladosporium citri Massee. Attempts to find a perfect stage of 

 the true citrus-scab fungus were made by Fawcett without success. 

 Citrus plants subject to attack by this fungus are mentioned and 

 control measures based on spraying experiments suggested. 



Stevenson {24) emphasizes the influence of weather on citrus-scab 

 outbreaks. His experiments for control show that in Porto Rico {26) 

 sulphur sprays were partially effective against citrus scab, while 



