14 



THE AGRICULTURAL NEWS 



Januaky 7, 1911. 



FUNGUS NOTES. 



THE BUD-ROT DISEASE OF PALMS 



IN INDIA. 



PART I. 



The results of a most thorough examination into the 

 cause of bud-rot in a district at the delta of the Godavari River, 

 on the east coast of India, have just been published in the 

 Memoirs of the Deji'irtment of A</i iculture in India, Vol. Ill, 

 No. V. The work was conducted by Dr. Butler, MB., F.L.iS., 

 Imperial Mycologist to the Government of India, who was 

 also responsible to a large extent for the organization of the 

 sj'steniatic campaign that has been undertaken to eliminate 

 the di.sease as far as po.ssiVile. The information given in this 

 and the next number of the Aifricu/tuvil News is taken from 

 the paper referred to above, in which Dr. Butler presents an 

 interesting account of the work. 



The di.sease appeared about the year 1890, and extended 

 regularly in all directions from the point originally attacked, 

 until, in 1910, it covered the whole of an area, approximately 

 circular, with an average radius of 25 miles. Although the 

 spread of infection has been very regular, yet it has been more 

 marked along certain lines than elsewhere. The-se lines cor- 

 respond generally with those of the main directions of 

 communication in the district. 



The portion of the country infected possesses a very dense 

 population engaged in agricultural pursuits, the crops grown 

 being of a very various nature. The district is one of the 

 richest in the Madras Presidency. The palms grown are the 

 Palmyra [Borassus flahellifer), cocoa-nut, areca-nut {Areca 

 Catechu) and date. Of these, the Palmyra is liy far the 

 commonest and of the greatest economicimportance,onaccount 

 of the extraordinary number of uses to which its various parts 

 can be put. It is also much the most susceptible to the 

 disease, though the cocoa-nut and areca-nut are also attacked 

 to some extent, the last mentioned being very .slightly suscep- 

 tible. 



As is well known, disea.ses of a similar nature are of 

 general occurrence in almost all parts of the tropics, and the 

 general tendency is to believe that the disease in the New 

 World is of bacterial origin. The Indian disease has defin- 

 itely been proved to be due to I'l/thiumpalmironnn, But!., 

 and Dr. Butler is of the opinion that some of the forms of the 

 disease found in the eastern tropics will {irove to be identical 

 with it, while the form in the New World is more probably 

 due to a ditierent organism. 



SYMPTOMS. The first external sign of the disease, visible 

 from below, is usually the withering of the central shoot, 

 which is followed by the death of the expanded leaves sur- 

 rounding it. These leaves turn pale and wither, and at the 

 end of ten or twelve days are dry and of a yellf)wish-brown 

 colour. The loaves die slowly from the centre outwards, and 

 eventually all fall off and only a bare pole is left. More 

 rarely, the first indication is the death of one of the expitmded 

 leaves near the central shoot; the <li.scase spreads inwards, 

 killing the central shoot, and then slowly com[iletes the des- 

 truction of the wlujle crown, as in the first ca.se. The final 

 stage is not reached until two or three years after the death 

 of the central .shoot. 



The fungus actually commences its attack on the out- 

 side of the folded leaf sheaths forming the covering surround- 

 ing the central bud. This is most likely to happen when 

 the outer leaves have been removed, and in consequence 

 a soft, green inner sheath has Ijoen exposed. In an}- case, 

 this stage of the disease only becomes visible when the outer 



leaves have been removed. The attacked area first appears 

 as a spot on the sheath, varying in size from a diameter of 

 6 inches to one when it is .scarcely visible. The spots are 

 white at first, but soon show small brown marks, which run 

 together UQtil the whole is brown; they then turn reddish, 

 and are usually sunken, with a raised rim. On the hard 

 outer sheaths, the final colour is often black. The fungus 

 travels in a horizontal direction, from the outer to the inner 

 side of the sheath. It then infects sheath after sheath, and 

 finally attacks and kills the terminal Inid, when the central 

 shoot withers. Thus, at the time that the first symptom 

 visible from below has become evident, the tree is practically 

 dead, as no further growth can take place. The leaves pene- 

 trated by the fungus in its progress to the central bud are 

 rarely killed. The reason is that the path of the fungus, 

 through all but the very soft central leaves, is practically 

 cylindrical, and apiiroximately of the same diameter 

 throughout. The amount of tissue destroyed in this 

 way is so small that the leaves are not visibly affected. 

 By the time the fungus has penetrated to the soft cen- 

 tral tissues, a general rot has usually set in, and the whole 

 bud has been reduced to a decaying mass. This makes it 

 a difficult matter to determine the true cau.se of the disease 

 when it has progressed beyond the initial stages. The rate 

 at which the fungus penetrates the sheaths increa,ses as it 

 nears the centre. The whole time occupied from the ilate of 

 infection to the death of the central shoot is usually from five 

 to ten months. The progress of the disease is often assisted 

 by the presence of small boring beetles, whose tunnels are 

 followed by the mycelium of the fungus. The spots on the 

 outermost leaf sheaths are usually hard, and either free from 

 the parasite or covered by a mycelial web. A similar mass 

 of mycelium is often formed between two leaf sheaths that 

 are not in very close contact with one another. A copious 

 growth of mycelium of this nature is a peculiar character, for 

 a species of this genus. 



In addition to attacking the leaf sheaths, the fungus may 

 also occur on the expanded blades and on the petioles. On 

 the leaf blades, the spots rarely attain more than 1 inch in 

 diameter, and are frequently smaller. They are straw-coloured 

 in the centre, with a dark-brown margin. Sometimes, a line 

 of such spots occurs, running across the leaf segments, one 

 spot on each. This is due to the fungus having penetrated 

 the leaf while its segments were .still folded in the bud. 

 The line of infected tissue in this case is above the tip of the 

 growing point. The latter is not affected until the fungus 

 has spread <lownwards. vertically, in the soft, young tissues. 



In the case of cocoa-nuts, it is usually- found that no 

 fruit is formed, once the disease has penetrated so far as to 

 be visible from below. When young nuts do appear after 

 this stage, they always wither and fall off before attaining 

 maturity. The falling of the nuts in this way has also been 

 noted in Trinidad in connexion with the bud-rot disease in 

 that island. (See Agriealtural Neivs, Vol. I.\, p. 254.) 



SPREAD OF iNKKcTiox. Sporcs of i)arasitic fungi may be 

 carried from one host to another by wind, by animal agencies 

 such as insects and birds, or by man. In this case, it is prob- 

 able that very little infection is spread by wind, since the 

 spores of the fungus are not formed on the outer leaf sheaths, 

 but arise frequently on the mass of mycelium formed between 

 two adjoining sheaths. Occasionally, when two such leaves 

 are disturbcil by the removal, for some economic purpose, of the 

 outer one, spores may be liberated and carried by the wind to 

 healthy trees, but this happens comparatively rarely. Other 

 .spores might be set free when the old leaves ivf badly infected 

 trees die and fall apart. On the whole, however, this method 

 of spread is probably not very cfiective. 



