88 DISEASES 



of water, being sprayed so as to form a thin film on the 

 trees. Infected fruits should be burned or buried. 



Scale, Aster olecanium spp. These insects sometimes 

 occur in considerable numbers on cocoa trees. Several 

 trees in Grenada were completely covered with them, and 

 it was found necessary to cut down the trees and burn 

 them. What is known as " Black blight " is generally 

 due to the presence of a fungus, Capnodium sp., which 

 obtains its nutrition from the excreta of scale insects. 

 Trees badly attacked with scale should be cut down 

 and burnt. Mild attacks may be effectively treated 

 with the remedies advised for the extermination of aphis 

 and mealy bug. 



The Lac Insect, Tachardia Albizzice, Green. The 

 branches of the cocoa tree are occasionally attacked in 

 Ceylon by the Lac insect. Green (Tropical Agriculturist, 

 October 1905) does not consider it does much damage, 

 although young growths are occasionally killed by its 

 work. 



Deimatostages contumax is the name given by Kuhlgatz 

 to a bug which affects cocoa trees in Kamerun. Strunk 

 (Der Tropenpftanzer, November 1906) tested various in- 

 secticides with a view to deciding upon an effective remedy 

 for this pest. He found arsenical compounds gave very 

 satisfactory results. Tobacco juice and soap solutions 

 also proved effective when applied at the commencement 

 of the dry season before the insects became abundant. 



Parasol Ants, Atta cepalotes and A. octospinosa, destroy 

 cocoa leaves in Trinidad. Parasol ants are so called 

 from their habit of cutting up leaves and flowers and 

 carrying them away on their heads to their nests. It is 

 stated that they seldom leave their nests during stormy 

 or heavy rainy weather, or while the sun is exceptionally 

 hot, so this should be the best time to attack them to 

 ensure the destruction of the whole nest. Hart recom- 

 mends the application of coal tar ; he states that it effec- 

 tively destroys the nest, and the ants never return to a 

 nest which has been treated in this manner. The " Uni- 

 versal Ant Destroyer," previously described, doubtlessly 

 could be employed with advantage for the destruction of 

 these pests, or carbon bisulphide might be applied to 

 the nests with equally good results. This liquid is ex- 

 ceedingly volatile, and the fumes which it gives off are of 



