K. M. Doiikjk 



Hosts and Varieties affected. 



The disease has been observed cm all the varieties of mango commonly 

 grown in this country, but all are not equally susceptible. 



The variety known locally as the Peach Mango or Figette is the 

 most resistant. This is a very fine-looking mango and keeps well, but 

 is said to be of inferior flavour. 



The most susceptible is the "Baissac" variety, known locally as the 

 " Long Green " ; the other three varieties which are commonly grown, 

 namely "Maison Rouge," "Corde" and "Dauphine," are almost as 

 badly affected. These are known locally as the "Long Red," or "Red 

 Kidney," the "Common Yellow" and the "Round Green," respectively. 



In view of the fact that so far as is known at present this disease 

 is confined to South Africa, search was made among nearly related 

 indigenous plants for a source of infection. In particular, the 

 "Maroola" tree (Sclerocarya caffra) was examined, as it is very common 

 in districts where the mango is grown. The only specimen of this 

 plant which showed any spots on the leaves proved to be infected with 

 Cercospora sp. ; and I have been unable to produce with the bacillus 

 causing the mango disease, any infections on the leaves or fruit of 

 the tree. 



Spraying experiments. 



A more detailed study of the progress of the disease was made during 

 the season 1911 — 1912 in connection with spraying experiments which 

 w T ere being carried out at Barberton in an orchard kindly placed at our 

 disposal by Messrs Winter Brothers. The season was an exceptionally 

 dry one, and consequently unfavourable to the spread of the disease. 

 The following table compiled from statistics furnished by the Meteoro- 

 logical Department shows that the rainfall has been much lower than in 

 the previous seasons. The temperature has been exceptionally high. 



Comparative Table. Rainfall 1907 — 1912. 



