176 H. A. BALLOU. 



remarks on drainage have been made at some lengtli because I believe that of all the 

 causes of the attacks of cacao thrips in Grenada, insufficient or bad drainage is perhaps 

 the most common, whilst the attacks of root diseases are nearly as often a cause. 



The other inducing causes of thrips, mentioned above, shallow soil with a hard or 

 heavy subsoil and a lack of organic matter in the soil, may be dealt with together. 

 These conditions should be apparent to any careful observer, more especially if it can 

 be impressed on all who have to do with cacao-growing that in the event of a severe 

 attack of thrips the first thing to do is to consider carefully the soil conditions. To 

 improve such soils, the subsoil should be opened up by deep forking or trenching, 

 followed by an application of lime and subsequent heavy and frequent applications 

 of organic matter in every available form. If the cacao-planter believes that the 

 attack of thrips is so severe as to interfere with the development of the pods already 

 formed, or if he is convinced that the trees are actually suffering, he may resort to 

 spraying as an emergency measure, but he should remember that spraying is only a 

 temporary expedient of no permanent value in itself. The effective control of 

 thrips will only be secured by the eradication of root disease, better drainage and better 

 soil conditions generally. 



The Cacao Beetle (Stirastoma depressum, L.). 



The cacao beetle has been known in Grenada for 25 years or more ; it is generally 

 distributed over the island and is probably well known to planters and small 

 proprietors. In abundance, it varies from being very plentiful in some districts to 

 very scarce in others. It is said to be most troublesome on the leeward side of the 

 island where it is to be found both on estates where great care is exercised and con- 

 siderable amounts of money are expended in efforts to control it, and on cacao which 

 receives little or no care. On the other hand, in certain districts this insect is not 

 a pest and does not occur in sufficient numbers to necessitate the adoption of remedial 

 measures, and this condition exists both where cacao is well cared for and where it is 

 neglected. 



There can be no doubt that the cacao beetle is a serious pest in places, and is capable 

 of becoming so in most other localities. In the Circular No. 1 of the Board of Agri- 

 culture, Trinidad, entitled " The Life-History and Control of the Cacao Beetle," 

 Guppy states that this beetle is the worst pest that the cacao-planter has to deal with. 

 I did not see any very bad cases of beetle attack in Grenada during this visit, but I 

 saw both the beetle and larvae and evidences of their work. On each estate the 

 thrips places were seen, because the planter generally regarded the thrips as more serious 

 than the beetle ; another reason for this is that thrips areas are definite and constant, 

 while, so far as I gathered, the beetle is not confined to any restricted area. It occurs 

 as a pest in several districts of the island, and often on certain portions of the estate, 

 but not as a pronounced feature on well defined areas. 



Good accounts of the cacao beetle, its method of attack, and measures to be adopted 

 for its control have been published by this Department. Pamphlet No. 58 entitled 

 "Insect Pests of Cacao, 1909," contains such an account, and more recently (1911) 

 the Trinidad Board of Agriculture has issued Circular No. 1, mentioned above, from 

 which it is learned that the cacao beetle may develop from egg to adult in about 80 

 days, as follows : — Egg 5 days, larva 63 days, pupa 12 days. The adult beetle may 



