524 



THE TROPICAL AGRICULTURIST, 



[December i, 1882. 



similar conditions and a clay subsoil are very general 

 in iJimbulla and adjacent districts. 



The Auatialiin eucalypti > Itliou.li they grow gener- 

 ally in aiid regions, ;, et ByLcially flourith on the 

 moist bill ranges of Feiushaw and Gippsland in 

 Victoria, up to 4,0UO feet altilude, wbich would be 

 fully the equivalent of 5,000 or 5,500 in Ceylou. 



As my sole object in this :ipplication is, if possible 

 (0 secure the mass of Cejlon planters from the 

 injury and loss which gum leaf disease has inflicted 

 on niysi If, I need scarcely say that I autioipate the 

 fullest puOlicity being given to tins letter and such 

 report as mny result from it, should the Governor 

 order enquiry and report. — I have the honor to be, 

 sir, your most obedient servant, 



A. M. Fergusok. 



Royal Botanical Gardens, Peradeniya, 

 15th Nov. 18>2. 

 The Hon'ble the Colonial Secretary, 



Sir, — With reference to my letter No. 61, of 27th 

 October, and your reply No. 67, of Nov. Ist, I have 

 the honor to inform you that the manager of Abbots- 

 ford esiate having forwarded to me, before any ap- 

 plication was made to him, specimens of the diseased 

 leaves of eucalypts and other plants, I was able to 

 malie a full exaniiiiatinn of them. But as it appeared 

 desirable to see the diseased trees in sUti, 1 proceeded 

 in accordance with your request, to the estate itself 

 and devoted a day to the examination of the growing 

 plants and their surrounding conditions in company 

 with the manager, Mr. A. M. Ferguson, junior. I 

 brought away numerous further speci" ens and have 

 since given to them as full an examination as I can 

 afford : — 



2. — From the letter to you (herewith returned) of 

 the proprietor of Abbotsforcl, it appears that the points 

 whicli he wisiied to have settled if possible was, 

 whether the orders which he had given to his man- 

 agers '*to eradicHfe every (Eucalyptiis) tree and burn 

 every twig and lent" were so well founded as to 

 justify him (I presume in liis capacity, as editor of a 

 local newspaper) in " advismg other planters to follow 

 his exain|ile." The matter thus seemed to acquire a 

 quasi-public character. 



3. — The theory on which this radical treatment is 

 based is this. Th'- di-ease, wliich was first observed 

 in gum trees on Abbotsford some lour or five years ago, 

 (soon after tlieir introduction tliere) showed little 

 severity and tendency to involve other kinds of 

 plants till the present year. It has now, however, 

 caused the death of many of the Australian eucalypts, 

 and it is believed that these have " infected" the cin- 

 chona, tea, and other plantain "more or lees proximity' 

 to them, many of which have died in I he same manner 

 as the gum-trees after having first exhibited similar' 

 spots on the leaves. It is the "malignant disease 

 in the leaves," which thus become " tiie source of 

 disease in other vegetation," that has principally 

 attracted attention, and it is hoped that by the 

 complete destruction of the euculypts as soon as the 

 spots appear, the disease maj be kept from spread- 

 ing to other plants in the vicinity. 



4. In the endeavour to ascertain wliat truth 

 there might be in this view, I first investigated the 

 leaf-spots with as much care as I am able to give. 

 They have precisely the appearance of being the 

 result of puncture by some small suctorial insect, 

 but, beyond their appearance, I cannot detect any 

 sign of such being the case. I am assured that 

 though carefully Searched for, no insects of this 

 sort (tree bugs) have ever been seen by any of 

 several observers, nor could I find any myself. It 

 is to be noticed too that it is vti-y rarely that thu 

 young and delicate leaves are attacked, the spotting 

 being in nearly all cases on the fully developed 



ones. As we have no evidence therefore of any 

 insect foe, that explanation of the damage to the 

 leaves may be abandoned. 



5. The question of a parasitic fungus being the 

 cause of the leaf-spotting is one more dithcult of 

 solution. I have carefully examined in a number of 

 cases the spots in all stages, and the zone of 

 thickened tissues surrounding the dead poition of 

 older ones ; but my results are purely negative. I 

 believe 1 am correct in asserting that in these 

 situations neither the mycelium nor fructification of 

 any fnrgus arc present ; with the exception that 

 upon the dried tissue one or two of the species 

 which affect such situations are occasionally to be 

 found. The spots commence as dark elevated 

 points or pimples, the principal change occuring 

 in the tissues being a morbid hypertrophy or 

 thickening of the cell- walls and probably an in- 

 crease of cell-produciiou ; gradually the chlorophyll 

 corpuscles disappear and the protoplasmic contents be- 

 come more or less thick, opaque and of a brown or 

 orange colour. Ultimately the cells dry up and die. 

 The process spreads outwards from a central point, 

 but does not extend far, resulting in a small de- 

 pressed brown or white, circular spot of dead tissue 

 surrounded by a slightly elevated border. The spot is 

 generally perfectly circular and about l-8th or l-6th 

 inch iu diameter but two or three may coalesce. When 

 the leaf is thin the centre often becomes perforated, and 

 when the spot occurs on the haider tissues (e. g. 

 the midrib) it present the appearance of an irregular 

 ulceration. 



6. It appears clear, therefore, that there are no 

 elements to be found in these diseased leaf-spots which 

 we can recognize as capable of conveying the disease 

 from one plant to another. This could only lieefifected 

 through the agency of some parasitic animal or veget- 

 able, neither of which is present. We are ignorant 

 of any other means of infection. The manager of the 

 estate endeavoured to demonstrate on the ground, that 

 each diseased Gum-tree was a centre, and that of 

 other plants, tea and cinchona for instance, the first 

 to show spots were always close to the Gums and to 

 leeward (i.e. North East) of them, whilst the only 

 plants that quile escaped were at some distance away 

 or to windward. I was not however able to satisfy 

 myself as to this constant relationship ; the number 

 of Gum-trees on the estate is very large and they 

 are widely distributed, so that it is not difficult to 

 point out one near and iu the required direction. 

 At the same time I cannot deny the jiroximity 

 of the diseased plants to one another, but this 

 is capable of a quite different explanation. 



7. Were the leafspots the whole mischief not much 

 harm would be done- I may .say here that such spots 

 are by no means new to me, nor, I should suppose, to 

 any ob-ervant person in this counlry. They are fre- 

 quently to be seen on both wild and cultivated jjlants, 

 especially in cinchona. Soma common jungle shrubs 

 are almost constantly so affected. But at Abbotsford 

 their abundant presence is unfortunately followed by 

 and seems lo be connected with more severe symptoms. 

 I can only corroborate the truthfulness of the descrip- 

 tions given by the proprietor and manager in their 

 communications to the Ohscrrrr as to the destruction 

 of irees and shrubs that has occurred on this estate. 

 In the eucalypts the younger branches and twigs shrivel 

 and die back, a local decay of the stem near the top, 

 usually '.ccompanied by enlargement, occurs, and the 

 portion above this perishes. I saw many trees of all 

 ages with the upper part and lateral branches dead and 

 dry whilst the main stem was yet alive and .still 

 endeavouring to put out new buds and branches. But 

 a further d.-velopment of the local "canker" soon 

 appeals lower down and before long the whole tree 

 succumbs, in cinchonas the morbid phenomena are 



