DISEASES AND PESTS 99 



occasionally found on the coco-nut, this is the only one 

 ever found in large numbers or charged with doing 

 serious damage. In the same genus, Aspidiotus, are 

 the San Jose scale, and a number of other pests of trees 

 of temperate lands. A. destructor is probably found 

 in every land where coco-nuts are grown. Beside the 

 coco-nut, it has a considerable number of other common 

 hosts, among them the papaya, annatto, betel-nut, guava, 

 and mango. 



The worst reports concerning this scale have come 

 from the Caroline Islands, the staple crop of which is 

 the coco-nut. The scale is said to have been introduced 

 from the Philippines in 1892, and a few years later to 

 have cut the crop in half. It is especially destructive 

 in dry places and during dry seasons. Dryness favours 

 the insects directly, because they do not endure great 

 humidity well ; and indirectly, because drought weakens 

 the host. Trees of all ages are attacked, and those 

 weakened by any kind of unfavourable conditions are 

 sooner or later killed. On arid ground whole groves lose 

 their natural green colour and turn a pale yellow, due 

 to the loss of the green tissues and the layers of scales 

 on the leaves. It is the local practice to sell the whole 

 nuts. No part of the crop is returned to the soil, which 

 grows steadily poorer, so that old groves have not the 

 proper strength to resist any attack. Young trees 

 planted under old ones do not receive light enough to 

 make them vigorous and able to resist. And the native 

 custom of eating the sweet "foot" of their seed-nuts 

 ensures the weakness and susceptibility of the seedlings. 



It should by no means be assumed that vigorous 

 trees are less subject than weakly ones to the attacks 

 of all pests ; but in the case of the scale this rule would 

 seem to be a good one. Therefore, to guard against 

 injury from it the trees should be amply spaced, provided 

 with plenty of water in the ground, and, if necessary, 

 cultivated and manured. If other pests or diseases are 

 present, it must be remembered that these will help the 

 scale to destroy the trees. 



