126 



THE AGRICULTURAL NEWS. 



April 13, 1912. 



FUNGUS NOTES. 



THE PANAMA DISEASE OF BANANAS. 

 Part I. 



Certain diseases of the banana, characterized by the pro- 

 gressive destruction of the water-conducting tissue in the 

 roots, bulb and leaf sheaths, have been known to exist in the 

 Western Tropics for some years, while a similar disease has 

 recently been reported from Bengal. These diseases are not 

 only spread over a comparatively large banana-growing area in 

 Central and South America and certain of the West Indian 

 Islands, but in some cases they have been responsible for very 

 serious damage, and have occasioned large financial losses. 

 In order to arrive at a clear understanding of the present 

 position of our knowledge of the subject, the history of these 

 maladies, as it appears in publications that have been issued 

 from time to time, may shortly be summarized. Such a course 

 is advisable, because the position is at present somewhat 

 complicated, and it is not yet clear how many of the different 

 forms of disease reported are attributable to the same organ- 

 ism, and are therefore truly identical with one another. It 

 should be clearly understood that this discussion relates only 

 to those diseases in which the vascular bundles, more espe- 

 cially in the rhizome, are destroyed and discoloured, usually 

 becoming dark-brown or reddish-brown. 



In 1903, Earle published in the Journal of the Neiv 

 York Botanic Garden, Vol. IV, p. 8, an account of a banana 

 leaf-blight in Jamaica, at Stony Hill. He stated that the 

 vascular bundles of the veins and midrib of the leaves became 

 brown; this was followed by the blackening of the entire leaf 

 blade, and the subsequent decay of the leaf and petiole 

 (leaf stalk). The disease did not appear able to extend from 

 the petiole into the tissues of the stem. The terminal bud 

 was not attacked, but continued to push out new leaves, 

 which were infected in turn, so that only three or four of the 

 younger leaves were healthy. Infected plants were much 

 stunted in growth, and did not bear fruit. Earle attributed 

 this disease to bacteria. It is worthy of note that the damage 

 appeared to be confined to the leaves, and to be incapable of 

 spreading to the stem, while there is no mention of any signs 

 of disease in the rhizome or in the roots. 



In April 1910, Rorer published a preliminary account of 

 a bacterial disease attacking the Moko Fig and French 

 varieties of plantain. Infected plants showed a drooping of 

 the leaf blades accompanied by a slightly yellowish tinge of 

 colour. This was followed by the breaking down of the 

 leaves owing to the collapse of the petiole at the base of the 

 leaf blade. The vascular bundles in the rhizome and leaf 

 sheaths were destroyed, and their colour changed to shades 

 varying from yellow to dark-brown or bluish-black The 

 preliminary note appeared in the Proceedings of the Agricul- 

 tuial Society of Trinidad and I'obago, Vol. X, pp. 109-13. 



In May 1910, McKenny published in Science, Vol. XXXI, 

 p. 750, a short account of the banana disease prevalent in 

 Costa Rica and Panama, and occurring by report on the 

 Atlantic side of Nicaragua, Honduras and Guatemala. The 

 symptoms of the disease as described by this writer are as 

 follows: — 



' Commonly the first external sign is a rapid yellowing 

 and subsequent browning and wilting of one or more leaves. 

 Sometimes there is a striking curvature and yellowing of the 

 terminal part of the leaf blade while the remainder is still 

 green. Eventually all the leaves die and fall back against 

 the trunk, leaving a crop of suckers which in turn are killed 

 and give place to still weaker shoots. The fruit of diseased 



shoots rarely matures and even when mature is worthless 

 with blotched, somewhat shrivelled surface and dry, pithy 

 interior. Shoots which develop after one or two suckers 

 have died rarely reach the flowering stage, when they do, 

 however, weak, distorted, worthless bunches are produced. 



' On cutting the pseudo-stem across and longitudinally 

 many of the bundles are found to be of a yellow, reddish or 

 reddish-purple colour, the colour deepening towards the root- 

 stock. In the last stages the colour of the bundles may be 

 almost black. While in recently affected plants the vessels 

 of the upper part of the stalk and the leaves may be normal, 

 those of the root stock are always coloured 



A nauseating odour is often given off when 



leaf stalks which have been diseased for some time are cut 

 open, though there may be no sign of rottting in the trunk.' 

 McKenny makes no definite statement as to the cause of 

 the disease beyond remarking that it is due to a vegetable 

 parasite, and recording the presence of both bacteria and 

 fungus hyphae embedded in the gummy substance blocking 

 cells and vessels of the xylem. 



In the same number of Science, Erwin Smith gives 

 an account of a disease of bananas found in Cuba. He 

 received material for study from that island and from it he 

 isolated a species of Fusarium, provisionally named Fusarium 

 cubense, which when inoculated into the midrib, leaf stalk 

 and psuedo-trunk gave a typical discoloration of the vascular 

 bundles; while from these the fungus was again isolated. 

 The disease was not given a chance to spread into the 

 root stock as the experiments had to be discontinued. 

 It remained to be shown if inoculations into the root 

 stock would give rise to the symptoms of the disease in 

 uninoculated leaves. This point is certainly of importance 

 because, as will appear later, the disease in Surinam is 

 due to a fungus having a Fusarium stage; and in this cast 

 the disease starts in the root and root stock, so that, if 

 the Cuba disease is identical with it, inoculations into the 

 rootstock are more likely to produce the disease in its typical 

 form than are those into the aerial portions of the plant. 

 In his account of the Cuba disease Smith writes as follows; — 



'The signs of the disease so far as I have been able to 

 obtain them from Cuban.s, and as the result of my own 

 examination, correspond quite closely with those described 

 by Dr. McKenny, and also to the banana disease described 

 by Mr. Earle from Jamaica in 1903. A similar, if not 

 identical, disease prevails in Trinidad, according to state- 

 ments made to me by ]\Ir. James Birch Rorer, from whom 

 I have also received alcoholic material. A .similar disease 

 occurs in Dutch Guiana, according to statements received 

 by me from Dr. van Hall, Director of the Experiment 

 Station in Suriname. I am inclined to think that the 

 Central American disease is also the same as this disease, 

 although we are not yet certain, Dr. McKenny and myself 

 having joined forces to settle, if possible, the problems 

 relating to banana diseases in these regions. Possibly there 

 are two banana diseases now- confused — one due to bacteria, 

 the other to fungi. 



'A microscopic examination of the Cuban material 

 showed bacteria to be pre.sent in some of the vessels, but 

 not in quantity sufficient to lead me to suppose them to be 

 the cause of the disease. In passing, I might say that 

 Earle sent me cultures of the bacteria isolated by him from 

 the diseased Jamaican bananas, and that in December of 

 1904 I inoculated these copiously into the leaf- blades and 

 petioles of bananas at Washington, but without production 

 of any disease ' 



In 1910, Levy published, in the Journal of the Jamaica 

 Agricultural Society, Vol. XIV, p. 241, an account of the 



