158 



rUK AGRICU'LTURAL NEW?. 



May 11, 1912 



FUNGUS NOTES. 



HEVEA RUBBER STUMPS AS POSSIBLE 

 CARRIERS OF DISEASE 



The importation of stumps of Para rubber has only 

 occurred to a very limited extent in the West Indies, since 

 l>y far the greater portion of the existing trees has been 

 grown from imported seeds. Yet occasional shipments of 

 stumps have been made from the Eastern Tropics, so that it 

 may not be entirely out of place to emphasize the need for 

 adequate supervision, to prevent these plants from affording 

 a means of entry for diseases, some of which are as yet 

 apparently absent from the Western Hemisphere, or at any 

 rate from the West Indies and Central America. 



In the Annual Report of the Botanic Gardens, British 

 Guiana, for 1910-11, Stockdale calls attention to the need for 

 some form of Government control in the importation of Para 

 rubber stumps into that Colony, in order to protect the rubber 

 industry. His argument is based on the fact that, though the 

 West Indian cacao die-back fungus, T/a/ridaria tarda ( = Di- 

 plodia cacaoicola) is now generally held to be the same as the 

 form common on rubber in the East, and formerly known as 

 Botryodiplodia elasticae and Diplodia rajmr, yet the extent 

 to which the West Indian form is capable of attacking Para 

 rubber is as yet not ascertained; at the same time, certain 

 shipments of stumps from the East have been found on arrival 

 to be covered with fructifications of the Eastern form of the 

 fungus mentioned above. In view of the possibility that the 

 Eastern form, though morphologically identical with the 

 Western, may have become more adapted to living on Para 

 rubber, it seems advisable that such infected plants should 

 not be allowed to enter these colonies. 



A further argument of the same nature may possibly be 

 advanced in favour of Government restriction of careless impor- 

 tion.s of rubber stumps. The brown root disease, due to Hymeno- 

 fhaete /(o,'' ('a, found on both rubber and cacao in the East, does 

 not appear to occur in this region; at any rate it has not been 

 found in any of the West Indian Islands where investigations 

 of root diseases have been conducted, nor does there seem to be 

 any report of its occurrence up to the present in any part of the 

 American Continent upon tropical species of cultivated plants. 

 The same woald also appear to be true of the root disease 

 caused by Fomes semitostiis — a fungus even more widespread 

 in its range of host plants and of even greater economic impor- 

 tance in the East than is f/y/nenachaete noxia. Finally, there 

 is in the East a pink disease common on a wide range of 

 host plants and caused by Corticium snlmonicolor. Although 

 there is an indigenous species, C. lilacinofuscum, in the 

 ^\'est Indies, which is similar to and possibly identical with 

 the Eastern form, yet the local fungus is not of great 

 economic importance and appears to be limited to a few 

 species, while the Eastern fungus is possessed of far greater 

 virulence. 



In view of these facts, it certainly seems advisable that 

 imported stumps of Para rubber from the East should be 

 submitted to some form of inspection; that diseased plants 

 should be destroyed and suspected stumps quarantined, and 

 subjected to reasonable preventive treatment. 



The risk of introducing diseases of Hevea at present 

 confined to the East, on seeds packed in charcoal and sent 

 by parcel post, is much less than that incurred when 

 stumps are imported. Annually increasing quantities of 

 seeds have been sent to the West Indies and British Guiana 

 during recent j-ears, and the fact that up to the present, 

 practically no disease has attacked the plants grown from 



them supports the idea that the seeds are comparatively 

 free from the spores of the commoner parasitic fungi, or that 

 these spores are unable to survive the long journey under the 

 conditions in which the seeds travel best. There is an 

 instance on record in which a disease did attack seedling 

 plants in the nursery, but it is not certain if this malady was 

 due to an imported or a local fungus; while adequate steps 

 were promptly taken, and the disease was thus easily con- 

 trolled and has not reappeared. 



It is almost impossible for the root diseases to be intro- 

 duced on seeds, since Hymenochaete nona hardly ever pro- 

 duces spores, in Ceylon and ilalaya; while Fames semitostus 

 would not be likely to be fruiting vigorously in the neigh- 

 bourhood of trees from which seeds would be taken. On 

 the other hand, the spores of Thyrklaria tarda are of very 

 common occurrence in the tropics while those of Corticium 

 salmonirolnr mighr also find their way to Hevea seeds; but 

 even so, the risk of infection from such a source is consider- 

 ably less than that arising from the presence of vigorously 

 growing m3'celium provided with an adequate food-supply 

 such as is furnished by a stump. 



RUBBER EXPERIMENTS IN UGANDA. 



A section is included in the Annual Report on the 

 Botanical, Forestry, and Scientific Department, Uganda, for 

 the year 1909-10, which has just l:>een received, dealing with 

 the rubber experimentation undertaken during that year. 

 In a general way, in regard to rubber trees growing at the 

 Botanic Gardens,' Entebbe, it is shown that the prospects of 

 Para rubber cultivation are most encouraging; this is not so 

 much the case with Funiiimia elastica, as the growth of 

 the tree is slow when compared with that of Para. A rubber 

 tree that grows rather well is Custiltoa elastica, but the 

 extent to which it is attacked by a borer (Inesida leprosa) 

 causes it to be of little economic importance to the Protecto- 

 rate. Better results have been obtained with Ceara rubber 

 {Maniho/ Glnziovii) which had yielded well on being tapped. 

 Manihot dichotoma and M jjiauhye/isix have been received 

 from Kew; the plants of the former have made exceedingly 

 rapid growth, and it is suggested that it might be used as 

 shade for cacao. ' 



In the period that is the subject of the review, two 

 experiments in tapping Para rubber trees were conducted. 

 Observations made during these and previous experiments 

 have led to the recommendation that the full and half 

 herring-bone systems should be adopted, the former for trees 

 with a girth at 3' feet of over 36 inches, and the latter for 

 those with a girth, at the same height, of 17 to 30 inches. 

 It is thought that the half herring-bone sy.-uiu will 

 eventually give the largest amount of latex, but thi.-, is not 

 yet certain. In any case, it has been demonstrated so far 

 that the prospects of Para rubber cultivation in Uganda are 

 most encouraging.- 



A trial was made for the purpose of ascertaining if the 

 Ceara rubber trees may be systematically and profitably tapped 

 on the herring bone system. The preliminary trials with 

 three trees have shown that, with paring and pricking on 

 consecutive days, the wound response was very rapid for 

 eleven days; from this time the daily yield decreased very 

 materially. It is intended to curry out further experiments 

 on a larger scale, at an early date. 



Roadside planting of rubber trees is being tried, with 

 varying results. An experimental forest planting of Funtumia 

 is making very fair progress. 



