fungus is known as a parasite on the cacao plant in Ceylon, 

 St. Thome (West Africa), Samoa, Java, Philippines, 

 Cameroons, and tropical America 



When a pod is attacked the shell darkens first at one end, 

 the darkening then spreading over its entire surface. The 

 mycelium permeates and destroys the entire substance of 

 the pericarp of the fruit and often attacks the seeds as well. 

 Attacked fruits are usually rendered valueless. 



The conidial form of reproduction of the fungus appears on 

 the surface of the pod as a white mould. Infection probably 

 occurs either at the stigmatic or at the basal end of the pod. 



Sexually produced oospores are formed in the tissues of 

 the pod and are capable of enduring a period of rest. They 

 are liberated when the pod decays. 



The fungus has not been reported to occur on any plant 

 other than cacao in the West Indies ; but in England it is 

 known as a parasite on many different kinds of plants, 

 more especially when they are in the "seedling condition." 



All diseased pods should be removed from the tree, and 

 these, along with any pods which may have fallen, and 

 husks or shells which may be lying about, should be buried 

 in pits with lime. Spraying with Bordeaux mixture has 

 given very good results, as may be shown from the 

 following : — 



In Ceylon, in 1902, ninety-six per cent, of the cacao 

 trees were attacked chiefly by Phytophthora omnivora, and 

 from fourteen to sixty-two per cent, of the pods were 

 diseased ; in 1903 the percentage of fungus pods was seven, 

 and in 1904 the percentage was four. The expenditure 

 was more than covered by the increased value of the crop 

 and the disease reduced to a minimum in three years. 



Spraying should commence when the pods are just 

 " set " and should be repeated at intervals of three weeks 

 until they are near maturity. 



Careful and thorough pruning is of special importance in 

 connection with this disease ; it ensures good access of light 

 and air to the lower parts of the plant, and thereby 

 diminishes those conditions of dampness and darkness 

 which are especially favourable for the development of the 

 fungus. 



Diagnosis : Hyphae variously branched, haustoria absent ; 

 conidiophores slender or sparingly unilaterally branched ; 

 conidia lemon-shaped, varying in size from 25 by 20 microns 

 to 60 by 40 microns ; oospore globose, smooth, yellowish- 

 brown, 20-30 microns diameter. 



HARTIG AND SOMERVILLE : Diseases of Trees, p. 38. 



MASSEE : Kew Bulletin, p. 1, 1899. 



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