174 H. A. BALLOU. 



Thrips by F. W. Uricli, published by the Trinidad Board of Agriculture, the same 

 belief is expressed. On referring to my report on my visit to Grenada in 1904, I find 

 that it is recorded there that in the case of an estate where a severe attack of thrips- 

 had taken place and where these insects were said to have caused the death of the 

 cacao trees, the thrips had occurred in November and December. During this 

 last visit to Grenada, I took every opportunity to obtain from planters information 

 with regard to the times of occurrence of thrips and the kind and amount of injury to 

 the trees. As a result, I formed the opinion that in Grenada, especially on those 

 estates which lie on the lower lands around the periphery of the island, the cacao 

 thrips is most abundant during the last three months of the year, October, November 

 and December, and that in the dry months a considerable improvement in the con- 

 dition of the trees takes place. 



With regard to the nature and amount of injury caused by thrips, I found that, 

 generally speaking, planters notice only the injury in terms of pods picked too green 

 and of labour and time lost in scratching the pod to see if it is ripe enough to be picked. 

 It is true that in some instances thrips are credited with causing the leaves to fall and 

 with preventing the development of pods when these are attacked while very young, 

 and it appears that in a few instances they are believed to have killed trees out-right. 



Thrips live and feed on the leaves and pods of the cacao. When leaves are attacked 

 they may be so seriously injured as to cause them to drop, but unless the entire crop 

 of leaves were destroyed and the destruction repeated in a short time, it does not 

 seem to me as if the tree would be seriously injured and it certainly would not be killed 

 from that cause alone. The attack on growing pods would not have any effect on 

 the health and vigour of the tree, even if all the pods were killed. In most instances, 

 planters have spoken of a severe thrips attack as being a time when thrips 

 were abundant on the pods, as a result of which the latter would be badly discoloured. 

 I have specially asked them to state how much damage has been caused to the crop 

 and how much permanent damage has been done to the trees. In nearly every case 

 the answer has been that very little shortage of the crop is traceable to thrips attack 

 and that the few leaves which fall are quickly replaced by new growth, but the loss, 

 occurs in the pods picked before they are ripe and in the loss of time by the pickers, 

 who often have to examine nearly all the large pods on the tree in order to know which 

 are ready for picking. 



I discovered a remarkable unanimity of opinion among Grenada cacao-planters 

 in regard to the occurrence of thrips during this last visit. In every instance where I 

 was shown thrips attacks or the effects of thrips I was told that " this piece gets it 

 every year," but in every instance something besides thrips could be shown to be- 

 wrong with the trees. Before considering what these other factors are, I would draw 

 attention to four points with regard to the cacao thrips in Grenada :■ — (a) Thrips 

 are present throughout the island, and at certain times it is doubtful if on those estates 

 where outbreaks of thrips occur there are any trees which are entirely free from this- 

 insect ; {b) thrips in the adult stage are capable of flight and the active young might 

 readily be carried from tree to tree by birds and large insects ; (c) thrips attacks 

 occur on the same limited areas year after year ; {d) thrips is a dry weather and a. 

 dry locality insect as a general thing, and yet in Grenada it generally becomes most 

 troublesome towards the end of the wet season. 



