DISEASES OF CACAO i6i 



nose fungus produces a similar effect. There can be little doubt 

 from the present aspect of affairs that a great deal of damage 

 which has been attributed to Diplodia was really due to Phytoph- 

 thora, which is not always conspicuous on the pods it destroys 

 and is quickly succeeded by saprophytes. 



On the other hand Howard and succeeding investigators 

 have found Diplodia capable of destroying pods to which it has 

 gained access by way of injuries and it very commonly attacks 

 pods which are over-ripe or have been left some time after 

 being picked. It is usually abundant on heaps of cacao shells. 

 This role agrees with that which it takes in connection with 

 sugar-cane and citrus fruits. 



History and Distribution. 



A. Howard, writing in 1901-2, regarded the pod-rot met with 

 in Grenada, Dominica, and St. Lucia as due to the fungus under 

 notice, and described it accordingly. He failed to recognise 

 the Phytophthora rot, believing it to be more or less confined 

 to Trinidad. He secured artificial infections which quickly 

 rotted the pods, but only through wounds. Van Hall and Drost, 

 who conducted infection experiments in Surinam, found the 

 fungus incapable of infecting sound, healthy pods, but able 

 to cause the decay of picked pods or pods which by some means 

 or other have been wounded or have already been attacked by 

 other fungi. With this statement Petch entirely agrees as 

 regards Ceylon experience, and in Trinidad Rorer has appeared 

 to attach little importance to the disease. It is recorded each 

 year from Grenada, St. Lucia and Dominica, but in view of the 

 difficulties of diagnosis it is uncertain how much reliance can 

 be placed on the differentiation between this and other pod-rots. 



Cailsative Fungus. 



This is described in connection with cacao dieback. 



Symptoms. 



The absence of the fructifications of the fungi described 

 under Phytophthora pod-rot and anthracnose, and the presence 

 from an early stage of the very different ones of Diplodia afford 

 the best evidence of this affection. Small pustules, densely 

 distributed, appear below the brown epidermis of the pod and 

 raise small projections which cause the surface to be very dis- 

 tinctly rough. From each pustule as it ripens is emitted a string 

 of spores which are white, grey or black according to the stage 

 of development they have reached. The white unripened spores 

 are one-celled, the black ripe spores are divided by a single 

 septum. Both forms are capable of immediate germination. 

 In damp air they hold together when emitted and form a tendril, 

 when dry they form little powdery heaps. The whole pod is 



