530 



Gang und Stand der Schweizerischen Landwirtschaft im Erntejahr 



1917. — [Swiss Agriculture in 1917 .}—Landivir(schftl. JaJirbmh d. 

 Schiveiz, Berne, xxxiii, no. 2, 1919, pp. 82-99. 



Apple trees were injured by Anthonomiis [pomorum] and stone-fruits 

 by Hyponomeuta. Injury by Cheimatobia [brumata] was less pro- 

 nounced. The vine-moths [Clysia ambiguella and Polychrosis botrana] 

 appeared later than in other years and were not very harmful. Owing 

 jjartly to comparatively late sowing, oats suffered considerably from 

 the attacks of the frit-fly [OscineUa frit], so that in some localities the 

 fields had to be ploughed up. 



B.4LL0U (H. A.). Report on Cacao Thrips, etc. in Grenada. — Bepr. to 

 the Governor of the Windivard h-lands, Grenada, 7th Februarv 1919, 

 pp. 2-14. [Received 15th October 1919.] 



The object of the investigations recorded in this paper was to 

 examine cacao ])lantations in Grenada suffering from attacks of the 

 cacao thrips \Heliothrip)S rubrocinctus] with special reference to the 

 value of spraying. The conditions with regard to thrips were much 

 the same as in previous years, though there has been some change in 

 the local incidence of this pest. On the whole, the south and west of 

 Grenada appear to offer the most favourable conditions for thrips. It 

 is expected that the cacao crop of 1919 will be a small one, which is only 

 to be expected after the unusually large crops of the previous years. 

 The lack of commercial fertilisers is also considered to be to 

 some extent responsible for the shortage of the present crop. 



The cultivation practised on cacao estates in Grenada is on the whole 

 very good, and still improving, more attention being given to the 

 construction of drains, and to the extensive use of manure, mulch and 

 soil covers. The connection between shade and drainage is discussed, 

 the cacao plants as a rule requiring more drainage when provided with 

 less shade, for if the growing roots are exposed under a thin covering of 

 soil to the hot sun without a sufficient supply of moisture, serious injury 

 will result. Probably this is the explanation of the frequently expressed 

 opinion that attacks of thri})s occur only in cacao with a western 

 aspect. Plantains, beans and other cover plants are frequently used 

 on exposed patches of soil. 



The practice of spraying cacao has been revived only since 1910. 

 Bordeaux mixture with Blackleaf 40 is considered more lasting in its 

 effect than soap and nicotine ; both mixtures kill a high percentage 

 of the thrips, but re-infestation occurs within a short time. There 

 are at present no figures available to show the amount of damage done 

 by thrips, but in some cases there is undoubtedly a considerable loss 

 of crop and some trees have died. 



It is considered very desirable that experiments should be under- 

 taken to determine the conditions that lead to outbreaks of thrips in 

 certain localities. In the author's opinion, injurious attacks of thrips 

 are entirely secondary and dependent upon some entirely physiological 

 condition in the plant [see this Review, Ser. A, iii, p. 582]. This would 

 explain the fact that many trees remain perfectly healthy although 

 thrips are present all the time. It is recognised by most cacao 

 planters that cultural methods are necessary in every attack of thrips ; 



