E. M. Doidge 4:; 



chloride, but less so to copper sulphate; not sensitive to sunlight; will 

 not grow without moisture, but is not easily killed by desiccation ; will 

 grow in media of widely different reaction, optimum reaction about 

 + 17 Fuller; maximum temperature for growth 45° C, thermal death 

 point 60° C. Group No. 221. 2223532. 



Summary. 



1. A disease of mangoes, hitherto undescribed, has for the last few 

 years been causing considerable loss to mango growers in the Union. 



2. So far as can be ascertained the disease is not known outside 

 South Africa, and it occurs in this country in the neighbourhood of 

 Barberton and Warmbaths, in the coast region of Natal and at Delagoa 

 Bay. 



3. Dark angular spots are formed on the leaves which do not 

 noticeably affect the general health of the tree, but serve as a source 

 of infection for the fruit. On the latter the disease causes discoloured 

 roughened areas and deep cracking ; infected fruit is detached from the 

 tree by the slightest air movement and falls rotting to the ground. 



4. Infection is carried by the wind, and by rain dripping from 

 infected leaves. Very few insects are found on the mango foliage. 



5. Spraying experiments have been conducted which show that 

 spraying with Bordeaux mixture, iron sulphide or Hycol is useless in 

 checking the disease. 



6. The cause of the trouble is a flagellate bacillus Bacillus mangi- 

 ferae n. sp. It invades the parenchyma, wedging apart and killing the 

 cells and causing gummosis; lignified tissues are not touched. 



7. The organism is described in detail and a resume is given of 

 its salient characters. 



Acknowledgment. 



I wish to acknowledge my indebtedness to Mr I. B. Pole Evans, 

 Chief Division of Botany, in whose laboratory the work was done, for 

 many helpful suggestions ; and to Mr E. E. Ensor of the Public Works 

 Department for adapting the apparatus described in connection with 

 the thermal death point determinations. 



The names of the varieties of mangoes grown in this country were 

 furnished by M. D. d'Emmerez de Charmoy, of the Department of 

 Agriculture, Mauritius. 



