39& 



THE AGRICULTURAL NEWS, 



December 13, 1919. 



PLANT DISEASES. 



RED RING DISEASE OF COCO-NUTS. 



The following is a report read by Mr. W. Nowell, 

 D.I.C, Mycologist, Imperial Department of Agricul- 

 ture, before a meeting of the Board of Agriculture, 

 Trinidad, on October 16, 1919, on the subject of the 

 3led Ring Disease of Coco-nuts:— 



I may perhaps appropriately take this opportunity of 

 putting forward a brief coiniunnication on a subject which 

 to coco nut planters is of no less importance than is frog- 

 liopper blight to cane growers. 



It may be remembered that during my last visit I had 

 incidental opportunities of making observations on the 

 so-called root disease of coconuts, and announced the invari- 

 able associatinn of the disease, in all cases examined, with 

 a minute thread worm or nematode. The matter was not 

 then sufficiently advanced for the issue of a report, and the 

 investigation is still far from complete. I had an opportunity 

 ct making some further progress with it in Grenada last 

 February, and during my absence on leave, some experiments 

 then begun have been completed and supplemented by 

 Mr. J. C. Moore, the Superintendent of Agriculture in 

 that island. 



An illustrated account of the disease was prepared early 

 in the year for the ITes/ Indian Bulletin, but owing to 

 •various delays has not yet appeared. It will now be out 

 of date in so far that some of the deductions made as to the 

 clevelopmeut and progress of the infestation do not agree with 

 the facts recently learned, but, as a description of the disease, 

 it remains, so far as I know, quite accurate. 



As this account will shortly be available, I propose to 

 »ive now only such general outline of present knowledge on 

 ihe subject as is appropriate to a business meeting. 



In the first place it must be stated that the connexion 



«f the disease with the nematode worm has been 



^abundantly confirmed. Not only is the worm pre.sent in 



close association with the first appearance of the disease 



in any organ of the plant, but infection experiments, 



with material to all appearances pure have resulted in 



complete and typical infestation of the inoculated 



trees with the reproduction of all the symptoms of 



the disease, the parallel controls remaining healthy. The 



proof cannot be considered absolute, but it conies nearer 



to certainty than is the case with very many plant di8ea.se8 



in which causation is regarded as established. 



The worm has been described as a new species* by 

 Jjr. N. A. Cobb, of the United States Department of 

 Agriculture, who ha? prepared a paper on its characteristics 

 for the forthcoming number of the U'lSl Indian Bulklin. 



It is now clear that the existence of the disease 

 in the roots, though fairly general, is only secondary. 

 Kxamples have been seon in which the roots were affected 

 only in the slightest degree. The centre of infesta- 

 tion is the red zone in the stem, \ihich is simply 

 a vast breeding ground cf the worm. From this it 

 extends more cr less along the roots, and, what is much 

 more senou.-s in immediate results, to the leaves This 

 includes not only the mature and semi-mature leaves which 



progressively fail in the familiar manner, but the very- 

 youngest rudimentary leaves, only a few inches long, in 

 the centre of the bud. It appears to be this infestation of 

 the leaves which brings about the death of the tree. 



In plantations where the trees are uniform in age. the 

 disease typically appears first in widely and thinly scattered 

 cases when the trees approacli bearing age. This can 

 occur equally on virgin forest soil or on old cultivated land. 

 The worms may come from sotne unknown alternative host, 

 not coco nut, but the balance ot probability seems at 

 present to be with the conclusion that they are introduced 

 with the seed nuts. 



From the centres of infection thus established, the 

 disease extends to surrounding trees, and the resulting losses 

 can be very serious. I have already seen or hoard of 

 several instances in which they approached 30 per cent. 



The process of natural infection, and the length of time 

 required for development remain to be investigated. Three 

 trees in Grenada inoculated in the stem 1 to 2 feet from the 

 ground were fully infested and failing in sixty days A tree 

 inoculated in the stalk of a leaf had a rather general but not 

 fully developed infestation in seventy-four days. A tree ia 

 which material was placed among the leaf bases without 

 inoculation was fully infested in stem and leaves in seventy- 

 four days, while a tree similarly treated in one leaf base had 

 seventeen infested leaves at the end of the same period. 



It thus appears that infestation may take place among the 

 leaves without previous injury, and this can be conceived as 

 quite possibly occurring from dry inftcted material blow- 

 ing about, or from worms gaining access-to the leaf bases of 

 young trees from the soil. 



There is a large amount of detail work remaining to be 

 done with regard to the resistance ■ f the worms to dryness 

 and to chemical agents, to their distribution and longev- 

 ity in the soil, and other matters. This work is of aa 

 obvious kind, and, given the opportunity, there is every 

 prospect of approaching to a fairly complete knowledge of 

 the disease within a reasonably short time. 



It is clear that the only hope of control lies in prevention 

 and not cure, and the biggest practical difficulty is going to be 

 the disposition of the vast amount of infested material which 

 the dying trees contain. 



A paper on the distribution of dry matter and nitrogen in 

 the potato tuber appears in the Journal of Agricultural 

 feVwe for September 1919. The percentage of dry matter 

 in the potato tuber is lowest in the skin, and increases to the 

 inner corticel layer and decreases towards the centre of the 

 tuber. The nitrogen percentnge increases from zone to zone 

 in the opposite direction to the dry matter, but it tends to 

 increase with dry matter from the terminal to the umbilical 

 end at which the tuber is attached to the plant. These 

 results refer to the h'nglish potato. 



In the Antigua Sun for November 13, 1919, there i.s a 

 refortof the proceedings of a general meeting of the Antigua 

 Agricultural and Commercial Society, at which Mr. T. Jack- 

 son, formerly Agricultural Superintendent, was presented 

 with an address and honorarium in respect of his services 

 to the society. The Chairman, Mr. K Btyson, in the course 

 of his address, said it was his pleasant duty, on the eve of 

 Mr. .lackson's departure for Si. Vincent, to thank him espe- 

 cially for his valuable work as Honorary Secrttary of all 

 the co-operative associations connected with the Society. 



