382 



THE AGRICULTURAL NEWS. 



November 23, 1912. 



FUNGUS NOTES. 



SUGAR-CANE DISEASES IN PORTO RICO. 



In the Second Annual Eeport of the E.xperiment Station 

 of the Sugar Producers' Association, Porto Pdco, some inter- 

 esting information is given bj' J. Pi. Johnston on the more 

 important fungus diseases attacking the sugar-cane, and 

 some of the points made bj^ this writer might apply equally 

 to the same diseases found in the English islands of the 

 Lesser Antilles. 



ROOT DISEASE. The most important is the root disease, 

 which appears to be caused by at least two diiferent fungi. 

 The first is Marasmius sacchari, which has long been known 

 throughout the whole of the West Indies. The second is an 

 unidentified fungus of which the mycelium is characterized 

 by the presence of stellate crystals, but of which no fruiting 

 bodies have yet been found. Unlike Marasmius this latter 

 fungus does not appear to cement the leaf sheaths together 

 but is found as a white feathery mycelium at the base of the 

 lower leaf sheaths. Investigations with a view to determin- 

 ing if these root fungi of the sugar-cane occur on any other 

 host plants have revealed the fact that the stellate crystal 

 fungus is common on many grasses, more especially on such 

 E^s form dense growths, as an example of which one kind of 

 guinea grass (Paspalum hemisphaericiiin) is mentioned. It 

 is also stated that a root fungus has been found on corn, and 

 it may be advisable to mention here that such a fungus has 

 also been recorded on corn in Barbados and Antigua, and 

 that its mycelial characters are very similar to those of the 

 Marasmius root disease of the sugar cane. As a result of 

 this .Johnston recommends that land known to be infected 

 with sugar cane root diseases should not be allowed to lie 

 fallow with a view to their elimination, but that it should 

 be planted with some leguminous crop or some crop of 

 economic importance, other than corn. Another point men- 

 tioned is that ratoons of Otaheite cane were found to be 

 particularly susceptible to root disease. 



RIND disea.se. It is observed in Porto Rico that this 

 disease has close relation to the climatic conditions, and to 

 the presence of the moth borer. This was also found to be 

 the case to some extent in St. Kitts recently; while another 

 factor influencing the virulence of the disease would seem to 

 be the condition of ripeness of the cane, as mature or over- 

 ripe cane would appear to be more susceptible than green cane. 

 Instances are recorded in Porto Rico of severe attacks of this 

 disease on a cane, apparently D. 625, which was mature but 

 comparatively free from the presence of moth borer; also on 

 over- ripe Otaheite cane that was suffering from drought, and 

 in a third instance on nearly matured cane that was badly 

 infested with moth borer. 'The occurrence of this fungus 

 (i.e. rind fungus) at the base of the leaf sheaths has been 

 noted, but its importance there has not been sufficiently 

 emphasized. We have no data as to whether or not the fun- 

 gus at the base of the leaf sheaths aids in killing the leaves. 

 It probably does, but not to an alarming extent. We have, 

 however, observed, that at least in the case of Otaheite and 

 of D. 11 6, the fungus passes from the leaf sheaths into the 

 stalk, if for any reason the vitality of the stalks is lessened, 

 thus neither moth borer holes nor rotted tops are essential in 

 every case to the infection of the stalk by this fungus.' 



Another point of importance that has received attention 

 is the value of treating cuttings with Bordeaux mixture pre- 

 vious to planting. Johnston calls attention to the fact that 

 this treatment will not destroy the mycelia of fungi which 

 have already entered the stems from which the cuttings are 

 made, and that the first step of importance is the selection of 



cuttings free from disease, that is, showing no discoloration 

 at the cut ends nor the presence of the white mycelium of the 

 root disease on the surface of the rind. With regard to the 

 treatment itself, it was found, as has also been discovered in the 

 West Indies, that its effect is much more valuable during dry 

 weather than it is when the atmospheric conditions are moist 

 enough to ensure a good stand of canes; under such conditions, 

 its principal ettect is only to hasten the germination. Oil 

 plantations where a large number of cuttings fail to germinate 

 owing to attacks of the pine-apple fungus, disinfection is to 

 be recommended, but on estates that are comparatively free 

 from the disease it may not be necessary in a good season. 



RED SPOT OF THE LEAF SHEATH. 'In the Annual 

 Report of the Pathologist for last year it was questioned what 

 effect the presence of diseased leaf sheaths on the cuttings 

 might have on the subsequent stand of canes. The particular 

 fungus related to this question is Co-cospora malnar causing 

 the red spot of the leaf sheath Experiments were made 

 with Crystalina seed which is characteristically badly affected 

 by this disease. There resulted a difference in the number 

 of shoots arising from the cuttings, a difference, however, 

 clearly not due to the fungus infection. In comparing the 

 shoots arising from the two lots of cuttings, and the sub- 

 sequent growth of these shoots, absolutely no difference in 

 amount of disease conld be detected between the plants from 

 cuttings with diseased sheaths and the plants from cuttings 

 without such sheaths. All the plants had abundance of the 

 fungus and in no case could it be said to be doing any 

 material injury. The difference in number of shoots in these 

 experiments is due partly to the effect the leaf sheaths have 

 on the preservation of the moisture content of the seed and 

 possibly to protection in other ways.' 



'rhis red spot fungus is fairly common on several 

 varieties of cane in the English islands, but it has never been 

 believed to occasion any injury of importance. 



RED EOT disease OF THE LEAF SHEATH. Observations 

 were also made on a disease of the leaf sheaths occasioned 

 by a fungus having a white superficial mycelium with small, 

 brown, spherical sclerotia. This fungus may occasionally 

 penetrate the leaf sheaths and inflict a certain amount of 

 injury on the surface of the rind. In Porto Rico it was 

 found as a result of observations on a limited number of 

 stools, that no very serious damage was inflicted by the 

 fungus even when it was present in considerable quantity. On 

 the other hand, occasionally instances have been recorded from 

 other countries in which the fungus is believed to have 

 caused severe damage to growing canes, and Johnston states 

 that his 'observations must not be taken as proof that this 

 fungus is not sometimes injurious to canes but merely as an 

 indication that it is not always serious.' 



In his concluding remarks this writer states: 'over 

 twenty-five different fungi have been found • n different parts 

 of diseased and dead cane and are now being identified. It 

 is believed important to determine not only the fungi found 

 on living, green cane, but also those of badly diseased cane, 

 for many fungi even if not parasitic tend to reduce the sugar 

 content of the cane.' He also records that attention is being 

 given to the question of whether certain of the cane fungi 

 may not live on other host plants, and states that certain 

 small mushroons found on grass showed a resemblance to 

 those growing at the base of canes, while certain of the leaf 

 fungi of the cane have also been found on grass. It is 

 interesting here to note that a species of Colletotrichum, 

 C. lineola, almost indistinguishable from C. falcatum has 

 been recorded by Butler in India on the Guinea corn 

 (Aiidropoffon Sorc/hnm, var. vvhjaris), and by Edgerton in 

 Louisiana on broom corn {A. Sm-ghum, var. ie.it His), and 



