142 DISEASES OF TROPICAL PLANTS CH . 



m 



^^^* 



rufomaculans (Clinton) Sacc., the bitter-rot organism 

 of the apple. The rotten spots are sometimes circular, 



sunken, and usually 

 covered with a white 

 mycelium on which is 

 eventually produced 

 numerous salmon-pink 

 coloured spores. Fre- 

 quently the entire fruit 

 is destroyed. In cases 

 where the fruits are 

 attacked when quite 

 young, they become 

 dry and hang on the 

 tree for a year or more, 

 thus becoming a source 

 of infection for the 

 next crop. The dis- 



FIG. 60. Fruit rot of the fig, Glomerella rufo- \ , , , 



maculans. (Photo by C. W. Edgei ton. ) ease Can 06 Controlled 



to some extent by 



destroying the diseased fruit and the mummies, and by 

 pruning out and burning the dead twigs ; spraying with 

 Bordeaux mixture will be profitable in localities where 

 the rainfall is not too great. 



Another fruit rot is due to Botrytis cinerea, Pers., 

 but is not of much importance except where the figs are 

 grown under glass. 



Soft Rot. This disease (Fig. 61) is due to Rhizopus 

 nigricans, which is also the cause of the rot of the sweet 

 potato and many other plants. It attacks the ripe fruit, 

 causing it to rot, and producing the characteristic black 

 mould. It is especially common in wet seasons, and is 

 disseminated by means of the wind, rainfall, and insects. 

 It is especially severe on the thin-skinned varieties. 

 There is no very satisfactory way of controlling it, but 

 frequent picking of the fruit and protection against 

 insects may reduce its ravages to some extent. 



Leaf-Spot. This disease is due to a Cercospora, 

 probably C. fici, Heald and AVolf. On the upper side of 



