FUNGUS DISEASES IN THE WEST INDIES 107 



carried out in 1905 an average yield of r32 kilos, of 

 cocoa per tree was obtained in 1908. From another 

 block of trees which were lopped in 1905, an average 

 yield of 1'347 kilos, of cocoa per tree was harvested in 

 1908. 



The expenditure incurred by lopping and spraying is 

 estimated at Is. 8d. per acre, which was compensated 

 for by the increased yield obtained within two years. 



Lasiodiplodia. — The complete life-history of this fungus 

 parasite of the cocoa tree has not been fully investigated. 

 It occurs in cocoa plantations in San Domingo, Brazil, 

 and several of the West Indian islands. Barrett, who 

 spent several months in 1907 studying the various fungus 

 diseases attacking cocoa trees in Trinidad, estimated that 

 between 50 and 75 per cent, of the young cocoa fruits 

 are destroyed by fungus parasites in that island. Of 

 the total losses suffered from these pests he considered 

 90 per cent, were due to a species of the genus Lasio- 

 diplodia. It infects the fruits, stems, and branches, and 

 it is considered possible that the roots are also infected 

 by it. 



Infection experiments carried out at Dominica tended 

 to prove that this fungus is only weakly parasitic in habit, 

 and it was therefore supposed that infection might take 

 place through wounds. In Dominica the growth of the 

 fungus is said to be slow and trees may be infected for a 

 considerable time before they are killed. 



According to Barrett the disease known as " brown 

 rot " in Trinidad is due to Lasiodiplodia. The invasion 

 of the skin of the fruit, especially in its earlier stages, 

 occurs either at the tip or at the base. Spores lodging 

 in the sinus, at the junction of the pedicel and the fruit, 

 where moisture is more constantly present than on any 

 other portion of the fruit surface, may germinate and 

 effect an entrance through the cuticle into the tissues of 

 the fruit-wall. As rain and dew also collect at the 

 opposite or stigmatic end of the fruit it is considered 

 possible that germinating spores may less frequently 

 inoculate the fruit at this point. 



The mycelium of the fungus spreads through the 

 tissues of the fruit-waU and then attacks the mucilaginous 

 envelope of the beans and eventually the beans them- 

 selves. Infected fruits in Dominica and Grenada present 



