Session - Wednesday, zznd April, 9.00 a.m. DR. B. A. BOURNE, Chairman. The following paper was presented by MR. MARTYN

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1 Session - Wednesday, zznd April, 9.00 a.m. DR. B. A. BOURNE, Chairman The following paper was presented by MR. MARTYN Paper SUGARCANE DSEASES N THE CARBBEAN R. E. D. BAKER, E. B. MARTYN, and G. C. STEVENSON mperial College of Tropical Agricultztre, Department of Agriculture, Trinidad, and B. W.. Central Sugar Cane Breeding Station, Barbados, respectively.! NTRODUCTON The grass family provides the world's cereals, the bulk of its sugar and the chief subsistence of its flocks and herds, and in the tropics is seldom the victim of extensive disease epidemics. The rusts and smuts, so devastating to the cereals of colder climates, are of minor importance to tropical grasses, and the sugarcane is less damaged by disease than many of the world's major crop's. Multiplicity of forms and natural adaptation to the methods of the plant breeder enable its essential contribution, a high sucrose production per ton of stem, to be maintained in varieties as numerous as the diversity of circumstances under which it is grown. The plant Breeder has oveicome the threat to cane which developed when virus diseases affecting it, probably originating in the birthplace of cane itself, spread through the tropics, and the other major diseases of the crop have been similarly countered, the simplicity of the final product having made the geneticist's problem easier than with fruit crops. Many fact,ors, however, contribute to the final quantity of "sugar in the bag", and in assessing the part played directly by disease its importance must be judged in relation to the other factors concerned when breeding and selecting new varieties. HSTORY OF CANE N THE CARBBEAN Before considering the diseases of cane in the Caribbean we may recapitulate briefly the history of the crop in this part of the world, admirably set out by Noel Deerr in his recent History of Sugar. From its obscure origins in the Western Pacific cane spread during the early ages of history via ndia and Persia to the Mediterranean, and thus to the Canaries, whence it was brought to the Caribbean by Columbus on his second voyage, in t seems probable that some of the commoner fungi associated with diseases of the leaves, sheath and stem and of world wide occurrence on cane were introduced at this time. Until nearly the end of the 18th century this original introduction was the only variety grown in the Western Hemisphere, and after subsequent arrivals, it came to be called 'Creole Cane'. t is similar to a variety ltnown as 'Puri' which can be found in ndia today. At the end of the eighteenth century, however, a revolution in Caribbean sugar

2 PATHOLOGY SECTON ' production resulted from the introduction of the Otaheite or Bourbon cane from the Pacific, far superior to the 'Creole1 cane. Bougainville, the French navigator, brought this cane to Mauritius in 1768, whence several introductions were made to the French West ndies and thence to some of the British islands in the seventeen-eighties. Bligh, on his successful second voyage, introduced it direct to St. Vincent and Jamaica in 1793, and further spread through the Caribbean took place during the seventeen-nineties. Bourbon then remained the standard cane of the French and British West ndies and of the Guianas for a hundred years, though Cuba replaced it in 1840 by Crystalina (or Transparent) and Puerto Rico also, though to a lesser extent. t was indeed fortunate that no systemic or bacterial diseases were brought from the Pacific with these early introductions, but in fact the first report of a serious cane disease in this hemisphere was the occurrence of Gumming Disease in Brazil, in 1869, appareritly originating from an endemic grass. Apart from this; disease would appear to have been one of the least of the Caribbean cane planter's worries during the 19th century, though DEERR refers to a serious disease of cane of unknown cause in Puerto Rico in t was not till the epidemic disease of Bourbon at the end of the 19th century, with which Red Rot and Rind Disease were associated by Mycologists at the time, that cane diseases came into prominence and new varietieswere sought, a state of affa5rs that repeated itself twenty years later with the spread of mosaic disease in the area. The fertility of cane seed had been shown in Barbados in 1858, but it was not followed up until 1888, when it was again recognised both in Barbados and Java, after which the systematic breeding of canes was begun. With the consequent need for new parents, and the desire to obtain substitutes from other parts of the world to replace Bourbon, the exchange of varieties between cane growing countries, taking place without the rigid quarantine precautions now in vogue, was no doubt responsible for the spread of cane diseases generally. Mosaic, for instance, is believed to have come from Java, where the condition, but not the cause, had been recognised in 1892, to Egypt, thence to Argentina and from there to Puerto Rico. n 909 Sir JOHN HARRSON* stressed the inadvisability of importing canes into British Guiana, and the desirability of quarantining any such imports, but it is only in the last twenty or thirty years that strict *quarantine has become the practice in the Caribbean, and in its early days at any rate it was often evaded. Now no new cane variety should enter the area except via quarantine, and with the sugar planter's everincreasing awareness of the dangers of disease deliberate evasion of quarantine is, we hope, less prevalent. BACTERAL DSEASES, The bacterial diseases may be dealt with first, as in susceptible varieties they have caused much loss in the past, all occur in the Caribbean, and Leaf Scald, recently found in the Guianas, is at present a cause for concern there. 'Gumming' was the earliest cane disease rekorded of which the cause was known. t originated in South America. Leaf Scald and Red Stripe came from the Pacific and their exact origin appears to be un- 1 certain. ' Gumming Disease. (Xantkomonas vasculorum). This disease has been identified at one time or another in Barbados, St. Vincent, St. Lucia, Martinique, Dominica, Gua-, * Agricultural News V, p. 91, 1909.

3 R. E. D. BAKER, E. B. MARTYN, G. C. STEVENSON 897.nd,ne eaf un-. at ua- deloupe, Antigua, St. Kitts and Nevis, Puerto Rico, the Dominican Republic, British $ Honduras and also Colombia. t was originally reported from Brazil in 1869, where it did serious damage to the Bourbon cane, and it is considered likely that there it spread to cane from an endemic grass host. This seems probable, as ORAN has shown that there are several natural hosts in Mauritius, and the organism can be inoculated into others. The disease appears to have spread from Brazil to Mauritius and thence to Australia in cane variety importations, but how it came to the Caribbean is not known. From the outset certain cane varieties were found to be resistant, and with the presence of the disease in Barbados, resistance to it was an essential character introduced into all canes put out by the Central Sugar Cane Breeding Station. Puerto Rico reported it almost extinct in 1937, owing to the use of resistant canes and the same holds in Barbados today, where it is no longer found, even on susceptible varieties. t is rare everywhere now among modern canes, but might possibly be found in the Windward or Leeward slands on isolated stools of old fashioned canes in peasant gardens. t would be interesting to know if it still occurs in any cane in Brazil. Leaf Scald (Xant+omonas albilineans). This disease was at one time confined to the Pacific, but its presence in British Guiana was recognised in 1950 and in Surinam in in 1951 t seems probable that it was originally introduced to the Guianas in illicit introductions of P.O. J. canes from the Dutch East ndies in the twenties, which canes carried the disease though highly resistant to it. n consequence it escaped detection until the recent rapid extension of certain Barbados varieties, notably B , which are very susceptible. One of its most dangerous features is its carriage in immune varieties with scarcely any visible symptoms. The disease was reported in Brazil in 1943, but a report in the journal 'Sugar' (January 1952) that it occurs in Puerto Rico was apparently erroneous. Red Leaf Stripe (Xantkornonas rubrilineans). This disease, also originating in the Eastern Hemisphere, has been known in the United States of America (Georgia and Louisiana) since 1924, Puerto Rico 1929, is reported in Cuba and occurs also in Argentina and Brazil. ts presence in Barbados was reported in 1951, but it is believed now to have been there for at least fifteen years, and has doubtless been disseminated with Barbados seedlings. Search during 1952 discovered the symptoms in British Guiana and Trinidad, and in the latter the organismswas isolated and reinoculat,ed. t has recently been observed in Surinam and further search would probably show it to be present elsewhere in the Antilles. The modern Barbados canes, however, appear to be resistant and except for producing minor leaf symptoms, easily overlooked, the disease seems to be of little account in this part of the world. t probably becomes more readily apparent in abnormally wet seasons. Mottle Stripe (Xanthornonas rubrisubalbicans) is reported from Puerto Rico. VRUS DSEASES Mosaic, as mentioned above, is believed to have come to the Caribbean from the East ndies by way of Egypt, Argentina and thence to Puerto Rico, but as at least two skrains are bnown in the area, and as the nature of the disease was not understood in the early days, there was probably more than one introduction. The early P.O. J. varieties produced to resist sereh di~ease were tolerant to mosaic, which largely accounts for the world wide spread of the disease before it was recognised.

4 OGY SECTON ts history in the Caribbean is interesting. n 1916 it spread alarmingly in Puerto Rico and Cuba and as a result of the ensuing investigations BRANDES ( ) showed it to be a virus transmissible by Aphis maidis. AS pathologists conversant with the disease elsewhere visited the other West ndian islands, mosaic was recognised as such by them and found to be present in'barbados, Trinidad and Jamaica, in the latter island being widespread. t is worthy of note, however, that in no case apparently had the planters themselves reported cane as affected by any condition of disease. Mosaic seriously affected many of the popular canes grown in the Caribbean when it first appeared there, but despite losses on:some varieties, especially when the cane grew under unfavourable conditions, it is difficult to escape the conclusion that in the British West ndies at least the actual loss of sugar for which it was directly responsible was somewhat less than the alarm associated with this disease would have led one to expect, and some of the losses in tonnage attributed to it may in fact have been due to other causes. The disease was first countered by the replanting of badly infected areas with Uba cane, a variety originating in Brazil and talcen thence to Natal, and which was immune to the disease. This step, together with rogueing and careful selection of planting material, checked the spread. Subsequently the introduction of "s$ontaneum" blood into new varieties enabled resistance or tolerance to the disease to be combined with desirable qualities lacking in Uba. At present mosaic is known in Cuba, Haiti, the Dominican Republic, Puerto Rico, Jamaica, St. Kitts and Nevis, Guadeloupe, Martinique, Barbados, Trinidad and Surinam. Strangely enough it does not occur in British Guiana, despite the introductions that must have been made there for cane breeding by Harrison and Jenman, and it is not known in St. Lucia or Grenada. t was observed on newly imported cane in Antigua in 1924, eradicated, and has never been recorded there since. n the Lesser Antilles the strain occurring is a very mild one, and through breeding resistance to it for many years at the Central Cane Breeding Station the disease is practically extinct in Barbados and is only found in one or two areas of Trinidad on BH O(Z), a variety still used by peasant cane farmers. n Barbados today the strain appears to have become even milder than before, and varieties once artificially infected there with ease will now rarely take the disease. n Jamaica a strain producing more virulent symptoms occurs, to which some varieties considered resistant in Barbados readily succumb, although even when leaf symptoms are plainly observable the majority of the canes appear tolerant to the Jamaica mosaic. A similar condition is reported also in Puerto Rico and the Dominican Republic. t seems likely that the strain found in the Greater Antilles is similar to one of those found in the Southern United States, and it would be of great interest if these apparently different strains could be grown alongside each other for comparison. A further point of interest is the question of wild hosts. While worlters in other parts of the world claim that sugarcane mosaic may be observed on weed grasses, such symptoms have never been noted in Jamaica or elsewhere in the British West ndies, and there seems some doubt as to their occurrence in Puerto Rico, though in certain cases the grasses reported as hosts elsewhere are commonly found in the West ndies. As regards other cultivated hosts, Maize and Guinea Corn can both carry mosaic. t was once common on Maize in Barbados and can be found on this crop quite readily * in Jamaica, where legislation covers the cultivation of Maize or Guinea Corn too near to major cane cultivation.

5 R. E. D. BAKER, E. B. MARTYN, G. C. STEVENSON 899 CHLOROTC STREAK This disease was recognised in Puerto Rico and Louisiana in 1943, and again recent of Pathologists conversant with it in other parts of the world have resulted in its gnition elsewhere in the Caribbean, and it is now known to occur in British Guiana, ch Guiana, Trinidad, Grenada, St. Lucia, Jamaica, Guadeloupe and Martinique, and would probably reveal its presence in other of the Lesser Antilles, though it not been found in Barbados and it is not recorded elsewhere in the Greater Antilles. With the exception of one or two varieties reported as being particularly suscepin British Guiana (Co. 421 and D 14/34) the commercial canes in current cultivation do not appear to be seriously affected, though on some varieties (E, g. B. 4362) leaf are readily observable when sought. As recorded elsewhere, the symptoms seem to become more apparent during periods of high humidity. Further study of the disease in this part of the world is desirable and investigations as to its effect on germination are now being undertaken in Trinidad. How chlorotic streak came to be so widespread in the area is somewhat of a mystery, the more so owing to its apparent absence in Barbados, unless it has been present unrecognised since the days of more indiscriminate introductions. Serek and Streak Disease have both been reported in Brazil, the only records of these diseases in the Western Hemisphere. t would be of interest to know whether they still occur in South America. Fiji Disease is not reported in the Western Hemisphere. DSEASES OF LEAF, SHEATH AND STEM Downy Mildew (Sclerospora sacchari) does not occur in the Western Hemisphere. Ring Spot (Le$tosphaeria sacchari) is known throughout the world and together with other minor fungi such as Phyllosticta spp. found associated with leaf lesions has probably accompanied cane throughout the ages. Some mycologists have queried the exact succession of fungi responsible for the well known leaf symptoms, and the disease can vary in intensity with variety, environment and season. t only becomes conspicuous however on mature leaves and is considered to be of little or no significance in its effect on sugar yields. Eye Spot (Helminthosporium sacchari) can be the cause of considerable check to. - growth in cane. While in the South Caribbean it is little in evidence, further north, where lower temperatures are experienced in the winter months, it can seriously reduce the effective leaf surface area and has been especially noticeable in Jamaica. Varietal differences are marked, as also the effect of environment, a shortage of Potash being one factor often associated with the disease as also is the occurrence of heavy dews. Although the leaves that were badly scorched in periods favouring the fungus may be replaced by subsequent healthy foliage, there must be a set back to the cane when the disease is at its worst, and in the northern British West ndies resistance to Eye Spot is a factor that is worth some consideration in selection of new varieties. Brown Stripe (Helminthosporium stenospilum) occurs in Cuba, Puerto Rico and the Dominican RepuBlic. Search might reveal its presence, as distinct from Eye Spot, in the Northern British West ndies also. ts practical significance is, however, on a par with that of Eye Spot.

6 goo PATHOLOGY SECTON 1 Target Blotch, ascribed to an unidentified species of Helminthos~orium is recorded from Cuba. Cercospora Leaf Spots are of very minor importance. Cercospora vaginae, Red Spot of the leaf sheath, is of almost world wide report, and is probably an age old minor parasite of cane. Cercospora longifies, Brown Spot, is mentioned by Nowell as being recorded some fifty years ago in Trinidad and Puerto Rico and Cercospora kofilzei is similarly rather vaguely reported from Barbados, Trinidad and British Guiana and is listed for Cuba,, Both should be re-identified by a specialist on the genus and their existence supported by herbarium material in the Lesser Antilles and Guiana, though C. lolzgifies has been re-identified in Cuba within recent years. Red Rot (Physalospora tucumane~zsis), Rind Disease (Pleocyta sacchari) and Pineapple Disease (Ceratostornella paradoxa) are three world wide parasites of cane. The two former figured promincntly in the investigations of mycologists as to the causes of the epidemic disease of Bourbon cane at the end of the nineteenth century, but are now generally considered only as weak parasites. Similarly, Pineapple Disease in the greater part of the Caribbean is of little account. Puerto Rico, however, reported considerable damage from Red Rot in recent years and in some dry areas cane rotting before harvest is a serious factor in reducing yields, the pathogenicity of the associated fungi deserving investigation. Black Rot attributed to Ceratostomella adiposunz is reported from the Dominican Republic. Smut (Ustilago scitaminea) is known in Argentina and Brazil. Records of its occurrenceinbritishguiana and Trinidad made some fifty years ago are now realised to have been erroneous, and the disease is not found in the Caribbean area. Rust (Puccinia kuehnii) is recorded from the United States of America (Mississippi) and Guatemala (1942) but is not found in this area. t is rather strange that a rust of cane is not more widely distributed than it is, unless infection is confined entirely to the Pokkah Boeng (Gibberella fujilzuroi) is recorded throughout the Caribbean, as it is throughout the world. t is of no account in the area, and occurrences are confined generally to certain varieties and accompanying conditions. Sometimes confused in early records with the condition Bnown as "Tangle Top" the etiology of this disease is still not clearly defined. Top Rot. A condition known as Top Rot has been occasionally reported in British Guiana (1923-1gz6), in Barbados and elsewhere in the Caribbean, affecting generally a few stools, all within a small area. A bacterial breakdown of the bud region occurs, but the most striking symptom is the golden yellow colour of the leaves of the affected canes, probably due to toxins produced by the bacteria. The condition occurs generally after heavy rains, and recovery soon takes place, normal shoots replacing those in which the growing point was killed, and the yellow colour disappearing. The causal factors are not known, though believed to be physiological, but the condition is mentioned herc as being allied to Pokkah Boeng. liau Disease (Gnomonia iliau) is reported from Cuba. There are a number of records from the area of fungi associated with cane and listed as diseases, but the primary parasitic nature of the fungus is so doubtful that their deletion from disease lists would simplify matters. These include Schizophyllum Rot (S. commune), Dry Rot, Stem Rot and Diplodia Rot (Physalosfiova rhodina), Dry Top Rot (Plasmodiophora vascz~laram), Red Rot of the Leaf Sheath (Sclerotium rolfsii),

7 R. E. D. BAKER, E. B. MARTYN, G. C. STEVENSON Sheath Rot (Cystos$ora sacchari), Wilt (Ce$halos$orium sacchari) and Red Leaf Spot (Eriosfihaeria sacchari), which is of very minor significance. Sooty Mould, Ca$nodi.um spp. occurs as a direct result of the presence of insects on the leaves, and as such should hardly rank as a disease. ROOT DSEASES When the old noble canes were prevalent in the Caribbean, and long ratooning commoner than today, a number of fungi, such as Marasmius sacchari, Himantia stellifera and Odontia spp, were constantly referred to and pictured in Mycologists' reports, in association with "Root Disease". Today such organisms can only be regarded, when found, as saprophytes and the "Root Disease" attributed to environmental causes. Adverse circumstances of varying kind may cause the death of cane roots and parts of the root stock, and the condition known as "Salt Blight" or "Dam Bed Disease" in British Guiana and recently confused with Leaf Scald symptoms, is a case in point. There is, however, no primary root parasite, comparable to Pythium root rot, known in the Caribbean. ENVRONMENTAL OR PHYSOLOGCAL DSEASES ETC. Limestone Chlorosis, ron Deficiency or Ratoo~z Chlorosis is commonly found on calcareous soils in Jamaica, is very prevalent in Antigua, has been sometimes recorded in Barbados and doubtless occurs on similar soils in other areas. A similar condition has been observed on young cane in British Guiana. Various chlorotic symptoms may be noted on cane from time to time, attributable to nutritional causes and generally only lasting for a short period in the growth of the cane. Banded Chlorosis. A condition apparently similar to that described in the Pacific - - has been noted on a few canes in Jamaica. t is doubtful however whether temperatures there are as low as those reported to cause the condition in Queensland, but it has also been recorded in Cuba as "cold chlorosis". Manganese Deficiency. Chlorotic conditions similar to those described and figured for Pahala Blight have been seen once in Jamaica and a deficiency of manganese was found to occur in the small area concerned. Lighteni~zg nj.ury is recorded from Puerto, has been observed in British Guiana, and is probably encountered occasionally in other parts of the area when heavy thunderstorms occur. CONCLUSON As would be expected, there are a rather larger number of cane diseases reported from the Eastern Hemisphere thail from the West. The Caribbean has escaped some of the systemic diseases of the East, and it is to be hoped that with moclern quarailtine precautions they may continue-to be lrept out of it. The chief danger lies in the unwitting iiltroduction of a symptomless carrier, the manner in which apparently Leaf Scald came to Guiana. One point that malres itself very evideut in the history of cane diseases is the value of visits of pathologists from other areas, who can generally observe a disease, common in their own country, which is easily overloolced when it finds its way to a new area where it is not expected and the symptoms are not well lmown. The pointing out of Mosiac, Chlorotic Streak etc. in the Caribbean, where they had been overloolred, by visitors well acquainted with them elsewhere are cases in point. 11 conclusion it is to be hoped that a list of world diseases of cane, which it has been entrusted to a standing committee of this conference to prepare and maintain at its triennial meetings, will malce clear the distinction between the important and well recog~lisecl sugarcane diseases of the world and the multiplicity, of minor ailments, weak parasites and saprophytes of cane which if listed at length tend to obscure the essential information needed.

8 902 PATHOLOGY SECTON DSCUSSON MR. MARTYN opened the discussion by stressiilg the apparent differences between the two mosaic strains in the Caribbean area and aslred the Chairman whether these strains could be typed in the U.S.A. DR SUMMERS suggested that varieties such as C P. 31/94 and Co. 281 could be made available in the British West lldies for, typing purpqses, and stless was laid oil the desirability of usiilg the same standard cane varieties as differential hosts in different areas to compare mosaic symptoms. MR. MARTYN pointed out that mosaic in the Caribbean appeared to be less virulent nearer the equator and suggested that factors of temperature and light hours might have spme bearing on thls. He noted that sugarcane mosaic, though present in ndia, was reported to be not severe there MR ROBNSON stated that m the Pacific, the Queeilsland and New South Wales strains wele very mild. t was noted that Brown Stripe, Brown Spot and Mottle Stripe had been observed in Jamaica by DR. ABBOTT and MR. ROBNSON. t appeared from a discussioil on Polrlrah Boeng contributed to by DR MCMARTN, PROFESSOR BAKER, DR. ABBOTT, DR. WEHLBURG and MR. ROBNSON, that the name "top rot" was used in South Africa for a disease which it was agreed was the same as Polrlrah Boeng in the Caribbean and elsewhere, that Fusarzum monzlzforme, Gzbevella fulzkuroz and G monzlzforme were probably to be regarded as synonymous, and that successful artificial infection wlth this organism had been secured 111 Cuba. MR. MARTYN, replylilg to MR ROBNSON, stated that "top rot" 1x1 Barbados was sim~lar to that described n British Guiana and that this disease was quite distinct from Polrlrah Boeng. MR. ROBNSON noted that DR MATZ had demonstrated the occurrence of Dry Top Rot (Plasmodzophora vascularum) in Puerto Rico in Questions as to the occurrence today of Strealr and Sere Brazil, two diseases reported somewhat doubtfully from that country 1x1 thepast, could not be answered owiilg to the absence of a Brazilian delegate to the Conference MR. ROBNSON queried the listing of "red rot" as a minor disease in the B~ltish West ndies, but was informed that though at one time considered important it was now of little concern in the B.W.1, though known to q,quse considerable damage in Puerto Rico. n the absence of the authors the following two papers were talcen as read. Paper SUGARCANE DSEASES N PARAGUAY LUS A. ALVAREZ >, Econonzic m#ortance of Sugarcane NTRODUCTON 1 Sugarcane is one of the important crops in Paraguay. The area under production, represents approximately 4.70% of a11 cultivated land. The production is sufficient to take care of the local demand. n Paraguay, only 0.8% of the territory is cultivated. According Yo the census*, 15,459 hectares were planted to sugarcane with a total production of 316,163 tons of canes: The area of production comprises the central part of Paraguay, extending east of the Paraguay River, as far as Villa Rica and neighboring towns. n Paraguay, the first varieties grown were the so-called Natives (Saccharum officinarum) of high sugar content but susceptible to diseases and pests. n the year 1918,