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CACAO 185 



disease. When cut the tissues are found to be dis- 

 coloured. The bark splits and allows a brownish red 

 gummy fluid to ooze out. This gum dries and gives 

 the dark rusty appearance. In Dominica the disease 

 causes an abnormal number of flowers which never set 

 fruit, and these flowers are produced continuously 

 throughout the year. It is sometimes known as the 

 " flowering disease." This peculiar flowering is the first 

 symptom in Dominica. Similar flowering is said to occur 

 in St. Lucia, but is not so common. The cankers may 

 occur on either the branches or the main stem. The 

 leaves are reduced in size and yellowish. The rate of 

 spread of the patch varies, and it frequently girdles the 

 branches and sometimes the trunk near the ground. In 

 severe cases the wood becomes dark brown, but is said 

 not to be affected with mycelium to any great depth. 



It fruits most abundantly in the rainy season by 

 white pustules, which push through the minute cracks, 

 burst, and liberate the spores. In the perithecial stages 

 it is very easy to separate the two organisms. The 

 perithecia of Calonectria flavida, Massee, are yellow 

 in colour, while the perithecia of Nectria theobromae, 

 Massee, are red in colour. 



The Nectrias are wound parasites and are much 

 more common on the old than on the young trees. In 

 fact, they are said not to attack trees younger than six 

 years. They are worse in the shade than in the open. 

 Their life history is not well understood. 1 



Stem cankers are quite common in Barbadoes, but 

 the writer has been unable to find a satisfactory explana- 

 tion of their cause. They are probably due to some of 

 the Nectrias. 



An undetermined species of Nectria in Ceylon attacks 

 both bark and pods, causing the pods to blacken, become 

 dry, and shrivel when about two or three inches long. 

 Fetch has recently said that the stem canker in this case 

 is due to a different species of Nectria from the one on 



1 Recent investigations indicate that the primary cause of cankers on cacao 

 and Para rubber is Phytophthora faberi, and that the Nectrias associated with 

 these cankers are secondary fungi, chiefly saprophytic in nature. 



