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OBSERVATIONS ON INSECT PESTS IN GRENADA.* 



By H. A. Ballou, 

 Entomologist to the Imperial DejMrtment of Agriculture, British West Indies. 



The Cacao Thrips {Heliothrips rubrocinctus, Giard). 



This insect has been known in Grenada since 1898, and has been considered a pest 

 of cacao by planters and others. At the present time thrips probably occurs in all 

 parts of Grenada ; at least, I found it or saw the results of its presence in all parts 

 of the island which I visited, and I think I might say in every field. It was, however, 

 onlv in certain fields, and often in small areas in those fields, that planters considered 

 that damage had resulted. The remarkable thing about the occurrence of thrips is 

 that it appears year after year on the same areas, even on the same trees, though 

 sometimes spreading a little ; but a thrips area one year is Hable, or certain, to be a 

 thrips area every year. 



It appears that a sufficient amount of information is now available to enable a 

 general statement to be made as to the economic status of the cacao thrips. 



Mr. Lefroy stated in the report on his visit to Grenada, dated 3rd October 1900, 

 that the discoloration of the pods which results from thrips attacks makes it difficult 

 to tell when they are ripe and that this increases the cost of gathering, since the pods 

 have to be tapped or scratched in order that the pickers may be able to see their real 

 colour. Otherwise this insect does not appear in any way very injurious or trouble- 

 some, and none but a very simple remedy would be worth adopting. After he had 

 made two visits to Grenada with special reference to this insect, Mr. Lefroy sum- 

 marised the situation in the following words : — " Thrips may be regarded as a possible 

 enemy to cacao rather than as an actual pest. There does not appear to be any 

 serious cause for alarm at the present time and the chance of the cacao suffering 

 materially from the attacks of this insect is, in my opinion, remote " (" West Indian 

 Bulletin," ii, 1901, p. 185). 



This opinion appears to me to be applicable at the present time, the experience of 

 cacao-planters during the past fourteen years having served to confirm the early 

 belief as to the nature of the attacks. At the same time, it must be stated that the 

 cacao-growlers still refer to the injury done by thrips and they recognise on their 

 estates certain fields, or patches in fields, where thrips attacks occur year after year, 

 and they also want to know what remedies to employ to check them. 



Formerly I was under the impression that the cacao thrips was always most 

 abundant during dry weather and that wet weather was favourable to the plants 

 and unfavourable to the insect. This idea is based on observations, correspondence 

 and interviews with planters and others, and has been put forward in Departmental 

 publications and Agricultural Conferences from time to time during the past few years 

 and no exception to the general idea has ever been taken. In the Circular on Cacao 



*Extracted from a report sent by the Imperial Commissioner of Agriculture, B.W.I., 

 to the Colonial Office. — Ed. 



