Plant Sanitation, 



[February, 19i0. 



Other species are now being boomed, 

 the chief of these being Coffea congoensis, 

 but trials on a large scale for an extended 

 period have yet to be undertaken. 

 Coffea robusta is now being planted as a 

 catch crop in rubber ; it may yield a 

 paying crop under such circumstances, 

 but it is as well to remember that it is 

 not exceptionally resistant to Hemileia, 



From Costa Rica samples have been 

 received of a coffee disease which does 

 not appear to have been noticed in the 

 Ceylon coffee days. The disease affects 

 the beans only. The bushes on which 

 the diseased beans are found are quite 

 healthy, and the "cherry" does not 

 show any indications which would lead 

 one to suspect that the beans were un- 

 sound. But the beans are found to be 

 blackened and disorganised, and such 

 black beans have altogether lost their 

 natural aroma. The cause of the disease 

 does not appear to have been ascertained. 

 One observer states that the mycelium 

 of a fungus occurs in the blackened 

 bean«, but this is not regarded as defi- 

 nitely established, and the effect is 

 thought to be due rather to physio- 

 logical causes. The disease seems to 

 have been known for a long time, but 

 in recent years it has become more 

 prevalent and in some cases has des- 

 troyed eighty per cent of the crop. I 

 have not been able to find any record of 

 it in Ceylon, but a coffee planter from 

 Southern India informed me that it 

 sometimes occurs there on the second 

 crop. 



During August, 1909, an extensive fall 

 of leaf occurred on several of the older 

 Hevea plantations in Ceylon. In the 

 majority of cases the leaves were shed 

 from the terminal shoots all over the 

 crown of the tree, but a few trees be- 

 came quite leafless. On one estate where 

 the trees were exposed to the South-west 

 wind, the leaf fall was greatest on 

 the South-west side of the trees, In 

 some respects this phenomenon resembles 

 . "dieback," but it differs from the latter 

 disease in that bare shoots occur all over 

 the crown and not only at the apex. 

 The death of green shoots all over a tree 

 may be a sign of overlapping or of root 

 disease, but in the cases refeired to the 

 shoots were not dead, as a rule, and 

 neither of these causes could be held 

 responsible for the leaf fall. The leaf 

 fall was normal, in so far that the leaves 

 were cut off just as they are when the 

 trees " wintei," and no fungi could be 

 found on the leaves or on branches from 

 which the leaves were seen to fall, In a 

 Jew cases, the terminal shoots died, but 



this was exceptional. The specimens 

 sent in for examination consisted usually 

 of dead branches bearing growths of 

 saprophytic fungi which proved that 

 they had been dead for some time ; and 

 it was found on examination of the trees 

 that these branches were obtainable 

 from the interior of the crown of 

 affected trees. But dead branches occur 

 quite normally in such a position ; they 

 are killed by the shade, or because they 

 are weakened by being deprived of their 

 food by stronger branches, and they 

 have no connection with" the leaf fall. 

 A few dead trees were shown me, but in 

 every case death was due to root disease, 

 and the fungus (Fomes semitostus, etc.) 

 was quite evident at the collar. Root 

 disease was looked for in all cases but 

 was only found on two or three trees ; it 

 is quite certain that the general leaf 

 fall could not be attributed to this cause, 

 and moreover the subsequent recovery 

 of the trees negatives the idea. 



A similar leaf fall occurred in 1903 ; 

 and a comparison of the weather condi- 

 tions in 1903 and 1909, together with the 

 absense of any fungi on the fallen leaves 

 or bate twigs and the subsequent re- 

 covery of the trees, leads to the con- 

 clusion that this is purely a climatic 

 effect due to the prolonged rains of the 

 South-west Monsoon. Trees grown on 

 comparatively dry soils will lose their 

 leaves and become " stagheaded " if the 

 soil is waterlogged for any considerable 

 time, because their roots are deprived of 

 oxygen, and this appears to be the 

 explanation of the present phenomenon. 

 It was not confined to Hevea. On one 

 estate, defoliation occurred in the case 

 of jak trees as well as Hevea, and three 

 cases of leaf fall in tea were reported. 



It is of course a well-known fact that 

 Hevea has been planted with marked 

 success on swampy land. One such 

 plantation, which was flooded every 

 other week during the last South-west 

 Monsoon rains, was visited, and it was 

 found that no noticeable fall of leaf had 

 occurred. This, however, is not at vari- 

 ance with the reason given above, for 

 the trees in such situations develop an 

 enormous number of feeding roots at 

 the surface, so much so that one is at 

 times walking over a spongy carpet of 

 white rootlets ; their roots can therefore 

 obtain air even when the soil is water- 

 logged. This plantation, by the way. is 

 the one about which the erroneous 

 statement was made at the Rubber 

 Exhibition of 1908, that the trees were 

 planted in swampy land and soon died. 



Further details of this leaf fall, and 

 records of the rainfalls for the last six 

 years, have been included in a circular 



