14 



THE AGRICULTURAL NEWS. 



Januaey 6, 1912. 



FUNGUS NOTES. 



EXPERIMENTS ON THE CONTROL OP' 

 LEAF RUST OF GROUND NUTS. 



A leaf rust of ground nuts, due to Credo anic/iidis, has 

 been of common ocrurrence in the West Indies during recent 

 years, and has been under more particular observation in the 

 experiment plots planted with imported American varietie.?, 

 in Dominica, Montserrat and St. Kitts. Some account of it 

 is given in the West Indian Bulletin, Vol. IX, pp. 157 and 

 167. ^^~W .-■^^'■'-1 „■ 



The disease appears to be more usually confined to the 

 older leaves, but this is not always the case; while the opin- 

 ions of different observers throughout the islands as to the 

 amount of damage due to it have been somewhat conflicting. 

 The same is true with regard to the effect of control measures 

 in reducing its prevalence. In the season of 1909, Mr. W. 

 Piobson, Curator of the Botanic Station, Montserrat, e.\press- 

 ed the opinion that it undoubtedly affected the yield obtain- 

 able, by shortening the life of the plants and causing shrink- 

 of the nuts. In the following year, Mr. A. J. Brooks, then 

 Master-in-Charge of the Agricultural School, Dominica, con- 

 ducted experiments to compare the weight of nuts from, 

 and the number produced by, infected and healthy plants. 

 He found that the presence of the fungus did not have any 

 appreciable effect on the values obtained in each case, and 

 concluded that the damage due to it was negligible. More- 

 over, he reported that spraying with Bordeaux mixture and 

 dusting the plants with a mi.^ture of lime and sulphur did 

 not reduce its spread. But in the same year, Mr. Itobson 

 found that the results obtained by spraying with Bordeaux 

 mixture supported the theory that the fungus shortens the 

 life of the plants. His results were based on the general 

 appearance of the sprayed and unsprayed plots, and 

 on comparisons of the yields obtained from each. He 

 found that the sections sprayed remained green for 

 a longer period than those unsprayed, and that the 

 fungus appeared on the control plots in some ((uantity 

 at a date when it was absent on the sprayed portions. 

 In the case of each variety grown, the yield of nuts from the 

 sprayed portion was in excess of that from the control plot. 

 It should be noted, however, that the fungus appeared eventu- 

 ally to some extent on the sprayed plots, as well as on the 

 controls. This is possibly due to the fact that spraying was 

 commenced at too early a date, or perhaps a third application 

 was advisable. The plots were planted on July 7, and were 

 sprayed on August 23 and September 17, while the rust did 

 not appear at all until the beginning of October: so that 

 a third aiiplicatioD'at the commencement of the month might 

 have been of service. Mr. Robson found that Bordeaux mix- 

 ture adhered well, but that an application of lime and sulphur 

 made on August 23 was washed oft' by a shower which fell 

 ■ soon afterward.':. (See Reports on the Botanic Station and 

 Experiment Plots, Montserrat, 1.910-1], pp. 12 and 13.) 



These results are at variance with those obtained in the 

 .same year in Dominica, but were confirmed to a certain extent 

 at that time by Mr. F. It. Shepherd, Agricultural Superinten- 

 dent, St. Kitts, who reported that rust appeared on the plants 

 in the experiment plots when the vines were maturing, but 



that spraying with Bordeaux mixture gave good results. No 

 evidence is available to show on what basis this statement is 

 made, so that its value in this discussion is limited. 



In the present season, Mr. Robson repeated the previous 

 experiments. In a summary of the results obtained, the fol- 

 lowing information is given. Rust was prevalent in all the 

 plots under cultivation at the Botanic Station, Montserrat, 

 but the Carolina Running variety ajipeared to suffer most, and 

 the Gambia least of all. Spraying experiments with Bordeaux 

 mixture did not yield any definite results; in fact they indi- 

 cated rather that little or no damage is caused by the fungus. 

 It was noticed that the actual number of rust pustules on 

 the sprayed portion was very small as compared with the 

 number on the unsprayed: but tests of the yield and quality of 

 the nuts from each set of plots showed no consistent results. 

 It should be noted, however, that the virulence of the attack 

 was not nearly so marked as it has I>een in previous years, 

 and this may account to some extent for the incon.sistent 

 weights of nuts recorded from the different plots of sprayed 

 and unsprayed varieties. 



This last piece of evidence appears to be in agreement 

 with that obtained in Dominica in 1910, and is decidedly at 

 variance, as regards j'ield of nuts, with the data recorded in 

 Montserrat in 1910. It seems possible that the nature of 

 the season may have some effect on the amount of damage 

 resulting from the attacks of rust: while another factor is 

 probal>ly the time of application of the fungicide, as well as 

 the number of applications made. The evidence available at 

 present seems to indicate that the damage due to the rust 

 fungus is so small that applications of fungicides, even when 

 effective, are not economically justifiable, as the resulting 

 increase in yield is insufficient to cover their cost. Further 

 experiments should, however, be conducted in order that, if 

 possible, some definite conclusions may be arrived at. 



EXPORTS FROM THE SEYCHELLES, 



1910. 



The following account regarding the exports and 

 trade prospects in the Seychelles i.s given in Colonial 

 Reports — Annual, No. (i9-^, p 9. 



The export of copra has risen steadily, and with improv- 

 ed methods of cultivation .should continue to progress. 



The export of soap and other products of the cocoa-nut 

 palm will only show an increase when there is a considerable 

 fall in the price of copra, but the quantity of nuts collected 

 is steadily advancing. 



A moderate crop of vanilla was harvested. Vanilla 

 plantations are being gradually restricted to the higher zones 

 of the mountains owing to successive dry seasons. With the 

 legislation in France arid the United States restricting artifi- 

 cial substitutes, there has been a continuance of the it-muner- 

 ative prices of the past two years, and as there is a growing 

 reluctance on the part of manufacturers to use the artificial 

 vanillin, there seems no reason why vanilla cultivation .should 

 not continue to form one of the princijial industries of the 

 Colony. I am aware that this opinion is contrary to that of 

 a number of experts. When in England in 1907, I was 

 told by a distinguished man of science, whose researches have 

 been mainly connected with tropical products, that planta- 

 tion vanilla was in its death throes. In that year the Sey- 

 chelles crop realized a million rupees, the price rose steadily 

 (apart from a temporary drop in lOOlS) and good prices have 

 ruled ever since. It is not as if vanilla has to be cultivated 

 at the expense of less capricious products: the orchid will 

 grow and thrive where cocoa-nuts and rubber will not. It is 



