19-2 COCOA 



Diseases and Pests. 



So far as it is possible to judge at present, Nigerian 

 cocoa growers are not troubled with more fungoid and 

 insect diseases than those of other countries. It is 

 probable that many of the diseases which exist could 

 be kept in check or even eradicated by the adoption of 

 better cultural and sanitary methods. 



Fungoid Diseases. The brown-rot disease of fruits, 

 Thyridaria tarda, Bancroft, in its conidial form Diplodia 

 cacaoicola, Henn., is ubiquitous, but does not do so much 

 damage as one would expect, considering that no com- 

 bative measures are employed. The non-employment of 

 shade trees is undoubtedly an important factor in check- 

 ing this pest, though, of course, this procedure is not 

 conducive to the general health and prolificacy of the 

 trees. 



An anthracnose disease of fruits, due to a species of 

 Colletotrichum, is also frequently met with. 



A stem disease, caused by a fungus new to science, 

 determined at Kew as Melanconium theobromse, probably 

 an imperfect stage of a Trichosphxria, is also fairly 

 common. But the etiology of this disease has not yet 

 been fully worked out. 



Thread blight, which is common in low-lying districts, 

 is considered to be identical with the one found in Java. 



The pink disease, Corticium salmonicolor, B. and Br., 

 has also been found in one district. 



The most serious root-disease is Hymenochsste noxia, 

 Berk., and this occurs in every district where cocoa is 

 cultivated. There appears to be little doubt that this 

 disease can be kept in check by isolating infected areas 

 with trenches and applying liberal dressings of lime. 



Poly poms lignosus, Kl., formerly believed to be Pomes 

 semitostus, Berk., has also been observed attacking the 

 roots of cocoa trees. 



Insect Pests. The most troublesome insect pest of 

 cocoa is the Melolonthid beetle, Adoretus hirtellus, Lap. 

 This insect attacks the leaves of young plants ; the 

 portions of the leaf between the larger veins are eaten 



