118 The South African Mulberry Blight 



Attempts at Control. 



All the ordinary fungicides have been tried in order to check this 

 disease, particularly Bordeaux mixture, but this has proved quite 

 useless. Mr F. J. Birkett of Dundee, who has been experimenting with 

 various methods, reports good results by using lime-sulphur as a spray 

 and cutting away a large quantity of diseased wood during the winter. 

 It is too soon to judge whether this treatment has been really effective, 

 but the pruning away of diseased material is certainly a sound step, 

 if the primings are promptly burnt. 



Infection Experiments. 



From the first specimens of blighted leaves from the Pretoria 

 district which were seen in November, 1908, a white bacterium was 

 isolated and numerous infections were obtained on two young trees in 

 the greenhouse by spraying them with a suspension of the culture in 

 distilled water. At that time the work was not continued as there 

 was other work on hand of a more pressing nature. 



In September, 1913, diseased leaves were received from Pietersburg, 

 and from these a white bacterium was again isolated. On the 25th of 

 that month a pure culture of the organism was suspended in sterile 

 distilled water and sprayed on a young mulberry tree (common variety) 

 with an atomiser. Numerous minute water-soaked spots were visible 

 on the leaves on the 30th ; these became larger and by the 9th October 

 were beginning to turn brown. Control trees sprayed with distilled 

 water showed no trace of infection. From spots on this tree the 

 organism was again isolated and with the second series of cultures a 

 second tree was inoculated. The leaves were sprayed as before and 

 the shoots pricked with a fine needle. In five days the characteristic 

 spots developed on the leaves, and on the stems in the neighbourhood 

 of the needle pricks a somewhat raised, water-soaked looking streak 

 which later became swollen and discoloured. 



What was apparently the same disease was observed at Blocm- 

 fontein, 0. F. S., and at Dundee in Natal. Spotted leaves collected 

 at the latter place in May, 1913, and kept dry in the laboratory yielded 

 vigorous cultures in August, 1914. On August 21st, a young mulberry 

 tree which was shooting out vigorously and had a number of young 

 leaves was sprayed with a suspension of a 48 hour old agar culture. 

 The shoots were pricked with a fine needle. Very numerous, minute, 

 water-soaked spots were visible on the under side of the leaves on 



