86 DISEASES 



of fruits, the attacks of thrips also cause discoloration, 

 which is often mistaken for that associated with ripeness 

 and sometimes results in the harvesting of immature fruits. 

 This discoloration of the leaves and fruits is mainly 

 caused by the thrips biting and feeding upon the plant 

 tissues, but in a less degree damage is due to the incisions 

 made by the females in which to lay their eggs. 



As trees in an unsatisfactory state of health are most 

 subject to thrips attacks it follows that the best means 

 of combating them is to remedy this by better attention 

 to the trees' requirements. 



Affected fruit shells should be buried with lime, and 

 the trees should be sprayed with the resin wash, whale- 

 oil soap solution, or kerosene emulsion described at the 

 end of this section. 



Aphis. Aphides, or plant lice, are frequently found 

 attacking the young foliage, flowers, and fruit of cocoa 

 trees, and their presence is often indicated by the ants 

 which follow them for the honey-dew, or sweet fluid, 

 which they exude and upon which the ants feed. The 

 distorted appearance of mature foliage is often due to 

 aphis attacks upon the young growths, and the develop- 

 ment of young flower-buds is sometimes prevented by 

 similar attacks. Spraying the trees with kerosene 

 emulsion or Avhale-oil soap will generally rid them of 

 these pests. 



Twig Girdlers. Various forms of twig-girdling insects 

 have been found attacking cocoa trees in the West 

 Indies. In Trinidad, Ecthoea quadricornis, Oliver, and 

 Tomicus sp. have been observed cutting off small cocoa 

 twigs. Another twig girdler, Oncideres amputator, some- 

 times attacks cocoa trees in St. Vincent and St. Lucia. 

 The female of the species gnaws the wood of a twig, and 

 before the twig falls lays an egg in the partially severed 

 portion. The larva, which hatches from the egg, is 

 thus supplied with the dead or decaying material neces- 

 sary for its food. The only practicable means of checking 

 the attacks of these pests appears to be in catching 

 and destroying the mature insects and in burning the 

 twigs on which the eggs have been deposited. 



Mealy Bugs, Dactylopius spp., are another pest of 

 cocoa trees, but are only of minor importance. Like 

 aphides they frequently attack young leaves and flower 



