142 



THE AGRICULTURAL NEWS. 



April 27,1911 



FUNGUS NOTES. 



the; PANAMA DISEASE OF BANANAS. 

 Part II. 



In April 1911, Rorer published a full account of the 

 Moko disease of bananas and plantains in Phytopathology^ 

 Vol. I, pp. 4.5-9, a reprint of which was issued by the Board 

 of Agriculture, Trinidad. The disease attacks the Moko, 

 Creole, and French varieties of plantain, and the dwarf or 

 Cavendish banana, but does not usually affect the Gros 

 Michel. It has been proved by inoculation experiments to 

 be caused by a bacterium, to which the name of Bacillus 

 mvsae has been given. The symptoms of the disease, as 

 described by Rorer, are as follows: — 



'The presence of the disease is as a rule first detected 

 in the lower leaves. The leaf blades droop a little more 

 than usual and have a slightly yellowish tinge — symptoms 

 very similar to those brought about by drought. Soon, how- 

 ever, the petiole of one of the leaves gives way just at the 

 base of the leaf blade, and all the other leaves quickly break 

 down in a similar manner. Eventually the terminal leaf, 

 too, bends over and the plant dies and rots down to the 

 ground. 



'Transverse sections of the pseudo-stem show that prac- 

 tically all the vessels are discoloured, the colour ranging 

 from pale yellow to dark-brown or blui.sh black, and filled 

 with bacteria. The discoloured bundles run back into the 

 true stem and thence into the young suckers and buds. 

 Sometimes in badly diseased plants the tissues of the leaf 

 stalks and stems are broken down completely, so that fairly 

 large bacterial cavities are formed. 



'If transverse sections of leaf or stem are let stand for 

 a short time the cut surfaces soon become covered with 

 bacterial drops which have been forced out from the ends of 

 the bundles. If the sections when freshly cut are put in 

 large covered dishes away from the air, pure cultures of the 

 organism may be obtained directly from these drops. If the 

 disease is not severe, or a plant does not become infected 

 until it has just formed a branch of fruit it maj' remain per- 

 fectly healthy-looking, but many of the young fruits, or 

 "fingers" do not properly mature; they remain small and 

 eventually become black and rotten. In such cases it is 

 found that there are some discoloured bundles filled with 

 bacteria in the leaves, stem, fruit stalk, or fruits. When 

 diseased suckefs are planted the terminal leaf frequently turns 

 black and dries up, ,so that the plant dies.' 



The similarity of this description with that of the disease 

 in Panama and Costa Rica suggested to Rorer that they might 

 possilily be the same Further study, however, showed that 

 they were clearly distinct, the principal points of difference 

 being that Bacillus musae has never been isolated from the 

 vessels of plants attacked by the form of Panama disease 

 occurring in Trinidad; that in every case a species of Fusa- 

 rium has been isolated by Rorer from plants both in Trinidad 

 and from Surinam, which were attacked by the Panama 

 disease; that the longitudinal splitting of the leaf sheath — 

 a characteristic of the latter disease- is not found in plants 

 attacked by the Moko disease; and finally, that the Gros 

 Michel variety, which is the most susceptible to the Panama 

 disease, seems to be naturally resistant to the Moko disease. 



Besides this statement by Rorer of the existence of the 

 Panama disease in Trinidad, there is another mention by the 

 same author in the A nnual Report of the Mi/rotngixt. 1909-10, 

 published by the Board of Agriculture, Trinidad. Xo general 

 account, however, has as yet been issued of the form of the 

 disea.se present in that island. 



In April, 1911, Essed published in the Annals of Botany, 

 Vol. XXV, p. 343, an account of the Panama disease as found 

 in Surinam. He attributed the disease to a fungus, which he 

 named Ustilaginoidella musaeperda. This had a Fusarium 

 condition, and, in so far as this stage was found, his account 

 supports those of other workers. His description of this 

 Surinam disease differs from McKenny's description of that 

 found in Panama, principally in the absence of any smell; and 

 from Levy's account, in the facts that no rotting is recorded 

 in the Surinam form of the disease, and that the roots remain 

 healthy until the tissue at their base is affected. 



In the same -month, Basu published in the Quarterly 

 Journal of the Department of Agriculture, Bengal, Vol. IV, 

 p. 196, an account of a disease attacking certain varieties of 

 binana in the neighbourhood of Chinsurah. Part of this is 

 reproduced: — 



'The chief symptoms of the disease are: (1) the turning 

 yellow of some of the older though otherwise healthy leaves, 

 (2) the formation of one or more much reduced leaves at the 

 crown, (3) the gradual withering of the younger leaves, (4) and 

 finally, the breaking down of the plant. The disease pro- 

 gresses so rapidly, that in ten or fifteen days from the first 

 appearance of it, the plant is found dead 



'By cutting a plant transversely near the base of the 

 leaf sheath, the disease becomes noticeable; either as black, 

 brown or yellow spots, varying in size from that of a circle 

 3 or 4 inches across. In longitudinal sections these 

 spots appear like streaks, which seem to pass from the roots 

 upwards into the root stock and the leaf sheaths. In many 

 places where a young plant is still attached to another plant 

 the disease passes from the mother plant to the young off- 

 shoot directly through the point of contact.' 



A fungus having a Cephalosporium and a Fusarium 

 condition was isolated from the diseased tissues; numerous 

 bacteria, believed to be of a secondary nature, were also 

 present, as is the case in the forms of Panama disease preva- 

 lent in the West. 



The most recent contribution to our knowledge of the 

 subject has been made by Drost, in Bulletin No. 26 of the 

 Department of Agriculture, Surinam. This author states 

 that this disease is different from that prevalent in Panama 

 and Costa Rica, though it has long been known as the 

 Panama disease, and although it also attacks principally the 

 Gros Michel variety. He bases this statement on a compari- 

 son of Levy's description of the true Panama disease with 

 the .symptoms of the Surinam form as observed by him.self. 

 He proposes the name Surinam Panama disease, to distin- 

 guish it from the form prevalent in Central America. 



The principal symptoms of the Surinam disease are as 

 follows: (1) The occurrence of yellow spots on the leaves; 

 this is best seen in young plants; it cannot be t iken as 

 a definite symptom, as it may be occasioned by othii causes. 

 (2) The sudden appearance of one or more incompletely 

 developed leaves. Plants whose leaves were formerly healthy 

 may show this symptom when growing in infected soil, as 

 also may infected suckers when planted in healthy soil. 

 When it appears during the first development period of the 

 banana, it is an indication of a very strong infection, and 

 the bulb will be found on examination to be badly diseased 

 throughout. (3) Longitudinal splitting of the external leaf 

 sheath. This is usually found on infected soil, in cases 

 where the disease is spreading in from the outside; it is due 

 to the disintegration of the vascular bundles, which so 

 weakens the leaf sheath that it can no longer resist the 

 pressure of the still vigorously growing inner leaves which it 

 enfolds. (4) In the most usual form, plants of six months 

 or older, which have been previously healthy, show a soften- 



