"BROWN-POD" AND "DIE-BACK" DISEASES 101 



should commence when the fruits are just ' set,' and 

 should be repeated at intervals of two or three weeks. 



" The fungus is known to occur on other hosts ; in the 

 West Indies it occurs on the sugar cane, on Castilloa, and 

 has recently been reported to cause a root-disease of the 

 Coco-nut Palm ; in Ceylon it is said to cause the later 

 stages of a ' die-back ' disease of Hevea brasiliensis, and 

 also to occur on tea and on Alhizzia moluccana." 



In addition to the countries quoted by Bancroft, 

 Thyridaria tarda occurs in cocoa plantations in the 

 Gold Coast and Fernando Po. 



The life-history of this parasite was worked out by 

 Howard. The spores are produced just beneath the 

 epidermis in Pycnidia. They are first expelled in the 

 form of white powdery dust, which later turns black, and 

 consists of elliptical, uniseptate, brown-black spores. He 

 conducted experiments which indicated that the fungus 

 is a wound parasite and capable of readily infecting trees 

 in which wounds are present or those not in a vigorous 

 state of health. 



The fungus is facultative and able to live on both dead 

 and living fruits and branches. It is therefore obvious 

 that when the disease is prevalent, dead tissues should be 

 buried as a preventive measure. 



An experiment conducted on the La Perle estate, St. 

 Lucia, has shown that this disease may be defeated by 

 high cultivation, manuring, and attention to careful 

 pruning. It has been almost exterminated on this estate, 

 and the yield of cocoa is reported to have been increased 

 from almost nil to over 1,000 lb. of cured cocoa per acre in 

 six years. 



Thyridaria tarda causes serious losses to San Thome 

 cocoa planters. Its attacks are, however, mainly re- 

 stricted to the fruits, which it attacks in all stages. It is 

 most prevalent during the rainy season, in densely shaded 

 areas and in hilly districts where the atmosphere is 

 frequently saturated with mist. 



On one large estate which the writer visited the disease 

 was almost absent from those portions which were situated 

 at from 1 to 400 ft. above sea level, but gradually in- 

 creased in virulence from the latter elevation up to 

 2,000 ft. 



On some of the trees growing at the last-mentioned 



