and Magazine of the Ceylon Agricultural Society.— July, 1911. 



95 



morning the diseased spots had a copious growth 

 of white mycelium on their surfaces. On mi- 

 croscopic examination this proved to be a pure 

 growth of pythium. A small piece of mycelium 

 was carefully removed, mounted on a slide un- 

 der a coverslip in a drop of water, and irrigated 

 with fresh water. In removing the mycelium 

 care was taken to remove aerial mycelium only. 

 All instruments and the water used had been 

 sterilised. In half an hour the sporangia pro- 

 duced vesicles and on bursting liberated zoos- 

 pores. This went on rapidly till most of the 

 sporangia had discharged their zoospores within 

 the next half hour. The material used for in- 

 oculating the first 15 palms was similar to the 

 above. The water from the above culture on the 

 slide was washed into a watch glass and a drop 

 or two of this used to inoculate the last three 

 palms. This, though not rigidly fulfilling the 

 conditions of a pure culture, is the most that 

 can be done with a holoparasite. 



Eighteen young palmyra palms in one field 

 of Bhimavaram village were consecutively num- 

 bered from I to 18. The only criterion of 

 choice was that the palms should be small 

 enough to be operated on from the ground. 

 They varied from 3 to 12 feet in height. The 

 outermost dry leaf-sheaths were removed. The 

 inner dry ones had the attachment of ono limb 

 to the trunk severed while the attachment of 

 the other limb remained intact. Usually 3 or 4 

 leaf bases were so treated thus giving access to 

 the softer, less, changed, leaf-sheaths within. 

 These half-attached leaf-sheaths were held 

 aside, the inoculating material placed on the 

 outer side of the uncut leaf sheath just within 

 the last half-attached one. The half-attached 

 leaf-sheaths were then replaced in position one 

 after another. A cord of fibre was then tied 

 round to keep the leaf-sheaths in position. In 

 a few cases a fold or two of the fibrous material 

 attached to the leaf-bases was wrapped round 

 the leaf-sheaths and wetted with water. All the 

 operations were done to each palm before 

 beginning the next one. 



The surfaces of the newly exposed leaf-sheaths 

 on which the inoculating material was placed 

 were not sterilised. But as the leaf-sheatbs fit 

 very tightly together and were exposed for only 

 a few seconds, it is probable that they did not 

 contaiu any of the organism that causes this 

 disease. The palms were chosen in a place in 

 which it is known that diseased trees had not 

 occurred 



On the 18th of August the palms were exam- 

 ined and every one was found to have become 

 infected with the disease. Three of them had 

 died, i.e., the growing point was dead. The 

 number of leaf-sheaths that had been pierced 

 by the fungus varied from 1 to 11. Diseased 

 spots from the inner leaf-sheaths of two of the 

 palms were placed in a moist chamber and 

 developed aerial mycelium, zoosporangia and 

 zoospores which were identical with those op 

 the spots of the original diseased palm and are 

 pythium paimivorum. This experiment was 

 unexpectedly successful. It shows that when 

 the conditions of humidity are suitable as in the 

 monsoon a palm that becomes infected stands a 

 poor chance of escape. In most of these cases 

 the infective material was placed on the leaf 



sheath by means of a knife, either the small ono 

 ordinarily used for such work or the ordinary 

 katti of the tapper. At Kothapeta and Itam- 

 pudi similar experiments were carried out and 

 confirmed the above results. In each place a 

 tapper inoculated some palms himself by pas- 

 sing the tip of his katti over a diseased spot and 

 then touching the surfaco of the leaf-sheath of 

 a healthy palm. These palms carry infection 

 from one palm to another. 



(3) Insects. — Two large insects common in the 

 delta, the black rhinoceros beetle and the red 

 palm weevil are capable of carrying the myce- 

 lium and spores of the fungus attached to their 

 bodies and one or other or both are often found 

 in borings in diseased trees. In several of the 

 palms that were inoculated in the course of my 

 experiments the latter insect was found. When 

 a living leaf-sheath is wounded it exudes a sweet 

 gummy juice andthis seems to be the attraction. 

 In nature the beetles and weevils get into the 

 heart of the bud. The young pupae emerge with- 

 in the disintegrating mass of tissue and observa- 

 tions conclusively prove that they carry the in- 

 fective matter (mycelium and spores) from place 

 to place within the limits of a single bud. The 

 mycelium and spores of the fungus cannot 

 well help becoming attached to their bodies and 

 being carried away to healthy palms when the 

 insects take to flight. The experiment has been 

 tried of allowing a weevil to walk over a diseased 

 spot bearing sporangia and then confining it in 

 a cage on the outside of the leaf-sheath of a 

 palmyra, but the results are not yet available. In 

 Kamachandrapur, Lankalakod< r and other vil- 

 lages the disease has been observed to be severe 

 in the vicinity of the huts of the Midigas, a low 

 caste of people who live ontflesh. This has also 

 been remarked near the huts of fishermen. The 

 offal of carcases and fish afford good breeding 

 grounds and the number of insects being greater 

 in such favourable situations than elsewhere, the 

 number of palms visited is greater. I am con- 

 vinced that palm weevils and rhinoceros beetles 

 play a part in disseminating the disease. Ex- 

 actly to what extent has still to be found out. 



(4) Bikds.— Birds may conceivably spread the 

 disease. If they perched on an infected part of 

 a leaf or if they preyed on the insects that occur 

 in the infected parts of the bud, mycelium and 

 spores might easily become attached to their 

 feet or bills and so be carried out to other pa'ms 

 on which they might alight. The affected parts 

 of the leaves are seldom suitable places on which 

 to alight, and what birds, if any, prey on rhino- 

 ceros beetles and palm weevils is not yet known. 

 The opportunities that birds have of spreading 

 th6 disease will only be occasional. Besides the 

 rate at which the disease spreads is so slow and 

 the progress of the disease is so steady that it is 

 improbable that birds play any considerable 

 part in the dissemination. 



The evidence now available goes to show that 

 the disease is spread — 



(1) chiefly by palm climbers, 



(2) to a smallar extent byinsects (palm weevils 

 and rhinoceros beetles), 



(3) occasionally by the wind and by birds. 



8. The length of time taken to kill a palm 

 varies. At first when the disease is eating into 

 the bud no sign of ill-health can be seen by a 



