96 



The Supplement to the Tropical Agriculturist 



person standing on the ground. Only by cutting 

 off and examining the loaf-sheaths can signs ot 

 disease be detected. When the central bud has 

 been killed the young expanding leaves become 

 yellow. This is the first outward indication 

 that anything is wrong. Now the growing 

 point in the centre of the bud has been killed 

 no new leaves are produced. There is then no 

 hope of recovery. The palm, however, goes on 

 living for a time on the reserve food stored in 

 its tissues but the leaves gradually die till 

 nothing is left but a bare pole. The number of 

 leaf-sheaths that may be pierced by a series of 

 diseased spots in a liue varies. The highest 

 number I have seen is 29. Even in this palm 

 there were still 4 leaves besides the central bud 

 untouched by the fungus. It must have taken 

 several months for the fungus to pierce all these 

 leaf-sheaths. 



The length of time according to experiments 

 from the infection of the palm till the death 

 of the growing point and the withering of the 

 central expanding leaves varies from one to ten 

 months. From observations made in the field it 

 is believed to extend to almost two years. From 

 many enquiries made of residents in the delta it 

 appears that the time that elapses before the 

 palm is reduced to a bare pole may be up to 

 three years or more. 



Thus a palm may be affected from one to ten 

 months or more before it shows visible signs of 

 disease and after that may dinger for upwards 

 of three years. During this time there is very 

 little hope of recovery from the disease. 



9. Recovery .—A. very few cases of recovery 

 even after a great part of the crown has withered 

 have been observed. This is due to the growing 

 point having escaped injury. Nearly all re- 

 covered palms succumbed in a comparatively 

 short time to a renewed attack of the fungus. I 

 have seen only three examples of recovery.- One 

 of them subsequently died of disease and the 

 other two were cut down in order to discover 

 where the new shoot arose. It was found in 

 both cases that the original growing point had 

 beeu missed and had begun new growth. Thus 

 out of thousands of diseased palms under obser- 

 vation since the operations were first instituted 

 in 1906 only one case of recovery, that mentioned 

 above, has been observed. 



10. Dormant condition of the fungus. — The 

 fact that these cases of apparent recovery almost 

 invariably succumb later on. is an indication 

 that the fungus is able to pass into a state 

 of suspended activity. When the operations 

 were begun it was frequently observed that even 

 after a locality had been cleared of all dead and 

 dying palms, new cases of disease continued to 

 show. " At first these were believed to be new 

 infections conveyed in some manner unknown. 

 Then it was noticed that there was a difference 

 in the distribution of these cases as compared 

 with outbreaks which ware undoubtedly due to 

 fresh infections as when a village became at- 

 tacked for the first time. In the latter case the 

 deaths were in groups or often in one small part 

 of a village only, indicating spread from one or a 

 few early attacked trees. The deaths in villages 



that had been one or more times cleared of all 

 outwardly diseased trees occurred scattered 

 throughout the cleared area. In Amalapurvillage 

 such scattered oases continued to recur with 

 the greatest persistence. In two small areas 

 kept under continuous observation which had 

 been cleared of large number of diseased trees in 

 November, 1906, five subsequent inspections up 

 to September 1908, yielded fresh cases. It was im- 

 possible that outwardly diseased trees could 

 have escaped cutting on these occasions, since the 

 plots were close to the road through the village 

 which was frequently traversed by those in 

 charge of the work. Similarly outside infection 

 was scarcely to be thought of for the whole vil- 

 lage, as well as those adjoining had been very 

 thoroughly and repeatedly worked over, being 

 the head-quarters of the taluk where the cam- 

 paign was prosecuted with the greatest energy. 

 Examination of several of these cases showed that 

 the outar leaf-sheaths bore unmistakeable evi- 

 dence of previous infection, the old brown spots 

 on the outer sheaths being split and dried up. 

 The sheaths of at least two years' leaf supply 

 often remain attached to the tree, and there 

 was every reason to suppose that some of the 

 spots seen on this and other occasions on the 

 outer sheaths may have been two years old. It 

 is now believed that such old spots may serve for 

 a considerable time to restart an active phase 

 of the disease. This is probably brought about 

 through the tardy germination of resting spores, 

 which have several times been found in the dried 

 mycelial webs on the surface of old spots. The 

 mycelial growth resulting from the germination 

 of the resting spores is small and soon termi- 

 nated by the formation of one or two sporangia. 

 The spores from these would settle on the 

 sheaths in contact and might succeed in pene- 

 trating them, whereas from their small number, 

 and entangled posibion in the old sheaths there 

 would be little likelihood of the sporangia being 

 carried to other palms before germination." In 

 my investigation in the G-odavari I have several 

 times seen unmistakable cases where the disease 

 had become arrested within the bud. In one 

 case near Vijeshwaram in Kistna district during 

 an experiment an apparently healthy palm was 

 examined. The disease was found to have pene- 

 trated several leaf-sheaths. The diseased spots 

 were old and dry. These w ire cut away and 

 several of the next inner clean leaf-sheaths were 

 removed. Three months later the palm was 

 still unattacked. It is still under observation. 



Those who, while conducting the operations, 

 have been living a considerable time in the dis- 

 trict have observed that palms which have 

 diseased spots on their expanded leaves invari- 

 ably die. 



The length of time between infection and the 

 appearance of the first visible symptom has been 

 proved by experiment to extend to ten months. 

 From field observation it is estimated to extend 

 in some cases up to almost two years. This ac- 

 counts in a measure for the numbers cut out 

 month after month in some places. These are 

 not all cases of new infection but are the visible 

 results of infection that took place months be- 

 fore. This is another factor that has prolonged 

 the operations. 



