440 . 



there, and infests trees in good condition, in which, case spraying is the 

 only remedy. As a general rule it is well to have a uniform, and not too 

 light a shade over the cacao, for the thrips increases rapidly in open 

 situations. Laboratory tests have shown that contact insecticides 

 are unable to kill more than 60 per cent, of the larvae and probably 

 do not affect the eggs. If Bordeaux mixture, Paris green, and lead 

 arsenate are used, the thrips are quickly poisoned ; milk of lime is not 

 so rapid in its action. In the field a spray containing 2 parts by weight 

 of unslaked lime in 100 of water remained on the foliage for several 

 months and infestation was prevented. It is probable therefore that 

 the good results obtained in Trinidad with a combination of Bordeaux 

 mixture and nicotine sulphate are due to the Bordeaux mixture, and 

 that the latter may be replaced by the very cheap milk of lime. The 

 advantages as compared with contact insecticides are that the protection 

 lasts for months (as long as the covering is present), even single trees 

 may be treated, and there is no danger of re -infestation from adjacent 

 plants. The shade-producing properties of the covering probably 

 promote the vital processes of the plant. 



In a test described, 5 plots were sprayed with a 2 per cent, solution 

 of Bordeaux mixture containing 1 per 1,000 of Black-leaf 40 (nicotine 

 sulphate), 3 plots were sprayed with Bordeaux mixture alone, and 2 

 were left untreated. The difference between the untreated and treated 

 plots was very marked, but no difference was seen between the two 

 lots of treated plots. The action was purely protective, and when 

 much new leaf is formed spraying must be repeated. The under-sides 

 only of the leaves were sprayed, so that angle-nozzles are suitable. 

 It is better to spray a few trees thoroughly than to treat a large number 

 carelessly. Milk of lime must be well stirred. 



Reyne (A.). Bestrijding van den Cacaothrips door Bespuiting mit 

 Kalkmelk. [Combating the Cacao Thrips by Spraying with Milk 

 of Lime.] — Meded. Dept. Landhouw Suriname, Paramaribo, no. 16, 

 1st July 1920, 3 pp. 



A count was taken in May 1920 of the pods in the test plots referred 

 to in the preceding paper and it was found that the treated trees 

 averaged 5J pods more than the others. The cost per tree was about 

 3d. It is desirable that spraying should be energetically prosecuted 

 in the current year, and if it proves a success economically, cacao 

 cultivation will flourish anew. 



It is advisable to spray the plots where thrips appeared the previous 

 year. Furthermore, if after the chief rainy season one ordinary full- 

 grown leaf be taken from each of 100 trees and the thrips counted, 

 spraying will be justified if an average of one thrips per leaf is obtained. 

 In examining trees the presence of thrips or of fresh punctures should 

 be sought for ; rusty leaves and defoliated trees only prove that infesta- 

 tion has already taken place. Spraying should be done immediately 

 after the rains, in July and the first half of August in the case of a 

 normal year. The formation of new leaf renders a repetition of the 

 spraying needful ; spraying must certainly be done when the amount 

 of new leaf equals that of the old. As a general rule two appHcations 

 should be sufficient for old cacao and three for new. The good con- 

 dition of the spraying apparatus, and the careful application of the 

 spray to the under-side of the leaves are important factors in success. 



