THE AGRICULTURAL NEWS. 



Januaey 12, 1918. 



SPRAYING EXPERIMENT ON CACAO 



TREES. 



A paper by Mr. J. B. Rorer, Mycologist of the Board of 

 Agriculture, Trinidad, published in the Bulletin of the 

 Department of Agiicul lure. Trinidad and To/'uf/n, Vol. .\\^, 

 Part 3, 1917, describes a spraying experiment made by him 

 in 1916, for the purpose of testing the value of a combination 

 of Bordeaux mixture and nicotine sulphate as a control 

 measure again.'^t both the fungus disease, Phytophthora or 

 black rot of pods, and the insect pest, thrips. 



For the experiment, a field on an estate at Sangre 

 Grande, which in previous years had been very badly attacked 

 by thrips, was selected. The field contained 1,"200 trees, 

 and was dividid into three plots of 400 trees each. One 

 plot was sprayed, while the remaining two plots were left 

 unsprayed The whole field was very even in general 

 appearance, and had always received the same treatment 

 throughout in regard to pruning, draining, forking, etc. 



The trees were sprayed three times — August 23, Sep- 

 tember 14, and October 19, At each spraying 400 gallons 

 of mixture were used, made on the following formula: 5 ft. 

 blue stone and 51b. lime to every 50 gallons (American) of 

 water, to which was added 5i oz. of 'Black Leaf 40'. The 

 mixture was made in the usual way in 50-gallon barrels, 

 and the spraying was done with a spray motor pump No 2, 

 mounted on a barrel, with two SOfoot leads of hose, and 

 10-foot bamboo rods. Friend angle nozzles were used. On 

 each occasion six men were employed. 



On August 23 the trees were quite well covered with 

 young pods (chirellos), and adult thrips were fairly numerous 

 on the young leaves, especially thf'se on suckers (chupons), 

 and were evidently laying their eggs in the leaf tissue. 



The second spraying on September 1 4 was made chiefly 

 for the purpo.se of giving the young fruits additional pro- 

 tection from black rot, and to kill any thrips which had 

 hatched out since the first spraying. Between this spraying 

 and the third spraying the trees had made a considerable 

 amount of new growth, and some of the young leaves, 

 especially along the borders of the sprayed plot, were 

 being used by adult thrips for egg-laying, so that the third 

 spraying was made for the purpose of killing these thrips, 

 and also to give the fruit additional protection. 



The first picking was made on November 22, and there- 

 after pickings were made at intervals, varying from three 

 to .six weeks, until .June 11, after which time there was 

 practically no fruit left on the trees. 



Last year both thrips and black rot did a great amount 

 of damage throughout the Sangre Gran<le district, and 

 a marked difference could be seen between the sprayed and 

 unsprayed trees a.s earl^' as the middle of November, and 

 from that time on the difference became more and more 

 marked until the end of the crop. The unsprayed trees of 

 the experiment, as well as unsprayed trees "n adjacent fields 

 and estates, were very badly attacked by thrips, and were 

 almost defoliated towards the end of the year, which naturilly 

 resulted in a distinct loss of crop. On the other hand, the 

 sprayed trees remained in full foliage during the whole time 

 that they were under observation, and produced a very good 

 crop of cacao. 



The tabulated results of the pickings from the sprayed 

 and from one of the unsprayed plots of an eipial number of 

 trees show that it is advantageous to spray cacao in districts 

 where the phytophthora rot is jirevalent, and where the 

 trees are subject to repeated attacks by thrips, for without 

 any additional manuring, drainage, or other cultivation, the 

 400 sprayed trees yielded 4,371 more pods, and 4.765 more 



sound pods than the control trees, and the crop was extended 



to the middle of June. The total number of pods picked 



from the sprayed plot was 10,921, of which 9,93.'i were 



sound, while from the unsprayed the total w»s 6,550 pods 



picked, 5,168 of which were sound. Only 9 per cent, of the 



fruit from the sprayed trees was affected with black rot, 



while 21 percent, of that from the control was so affected. 



The total amount of dried cacao from the sprayed 



plots wa§ estimated as 1,082 lb. dried cacao from the 400 



sprayed trees, while the 400 unsprayed trees gave 72 lb. 



The cost of spraying was as follows: — 



120 lb. blue stone at 8c. $9-60 



120n).;iime "72 



1 gallon 'Black Leaf 40' 10 00 



Labour, six men for four days at 40c. 9'60 



Total *29-92 



When spraying is done on a large scale the cost of the 

 labour would be relatively less, because six men can spray 

 from 500 to 600 trees per day. 



The above figures show that the spraying, even three 

 times, of trees which are well cultivated, pays well; in fact 

 every spraying more than pays for itself, even if the trees 

 are only sprayed once. Each spraying helps to reduce the 

 amount of black cacao and to kill thrips 



The above account will doubtless be of interest to cacao 

 growers in other parts of the West Indies, probably especially 

 so in Grenada, where thrips has been causing a definite 

 amount of anxiety. 



TOMATO BREEDING IN ST. VINCENT, 



The following notes have been sent us tor publi- 

 cation, by Mr. S. C. Harland, B.Sc, Assistant Agricul- 

 tural Superintendent, St. Vincent. They will be read 

 with interest by many tomato growers in the West 

 Indies, some of whom will probably be glad to obtain 

 cuttings of Mr. Harland's F.l generation of hybrids, 

 with its desirable character of bearing all through the 

 year:— 



In the fifth ll^port of the Board of Commissioners cf 

 Agriculture of Porto Kico (issued 1917) there is a preliminary 

 account of hybridization experiments with tomatoes. It is 

 there suggested that it might be po.ssible to combine, by 

 cross pollination, the diseasc-iesisting ijualities of the native 

 varieties with the superior qualities of the introduced kinds. 



Some work of this kind has already been carried out in 

 .St. Vincent, and it is therefore desirable that some account 

 of the experiments should be given. 



The St. Vincent native tomato is characterized chietly 

 by thi' following features: it is perennial in nature, and grows 

 80 vigorously that a plant may produce branches several feet 

 long; the fruits are small — about 1 }, inches in diameter — ■ 

 regularly shaped and smooth, containing a large number 

 of seeds, and so acid to the taste that they are useful only 

 for putting in soups, etc.; the variety is quite unaffected by 

 the disea.se 'Blossom end-rot', although it seems to be occa- 

 sionally attacked by the bacterial disease due to IJacteriuiii. 

 Mlanacearuni; growth and fruiting apparently take place 

 throughout the year. It has been considered that the 

 St. Vincent native tomato is merely a degenerate strain 

 of .some introduced kind, but the writer cannot agree with 

 this theory. The type behaves as a pure strain, and is quite 

 constant in all the characters which have been studied. 



Cro.sses were made between the St. Vincent native ^nd 

 the variety I'ondero,sa. The latter is a great favourite 

 with West Indian growers, and is distinguished from 



