126 



THE AORICULTURAL NEWS. 



April 12, 1913. 



FUNGUS NOTES. 



RED ROT FONGUS AND THE SUGAR- 

 CANE IN THE WEST INDIES. 

 Part I. 



The conflicting views to be found in the literature dealing 

 with the parasitologj' of the red rot fungus {Collttotrichiau 

 falcaliuu) rendered it desirable to carry out in St. Kitts and 

 Barbados the series of inoculations to be described in a later 

 article, with the object of determining as definitely as 

 possible, under West Indian conditions, (a) the chief mode of 

 infection in the case of the growing cane; (b) the possibility 

 of infection by means of diseased cuttings of different 

 varieties, (c) the rate of development of the disease and the 

 conditions of susceptibility and resistance to it on the part 

 of the host plant. 



The experiments were arranged during August 1912, 

 and carried out during the following six months by F. W. 

 South, Mycologist to this Department, and W. R. Dunlop 

 (now Scientific Assistant). 



Before proceeding to a description of these experiments, 

 it is necessary to refer first to previous work on the same 

 subject in other parts of the world, and to indicate the 

 position that existed before the commencement of the present 

 investigation. 



TEKVIOU.^ WOKK. 



The earliest inoculations with C . falcatum were made by 

 Went, in Java. The introduction of the fungus by means of 

 pin picks produced the characteristic symptom of a white 

 spot in reddened tissue after ten days. In 1901, C. A. Barber, 

 in India, described the disease {Bui. Depart, of Land Records 

 and Ayr., Madras, No. 43, 1901) as being parasitic in one 

 district and saprophytic in another In cases where the 

 infection was considered to be due to infestation with moth 

 borer {Diatraea sacchara/is), this author found the symptoms 

 confined to a single node. Barber also noticed the presence 

 of more natural cracks in Indian canes than in those of the 

 West Indies, but did not consider this condition responsible 

 for infection. He was inclined towards the view tLat infec- 

 tion took place through disea-^ed cuttings, though apparently 

 he did not conduct any definite experiments to prove it. 



About the same time Tryon, in Queensland, stated 

 (Queensland A<jr. Jown., July 1901) that C. falcatum 

 ■was there a faculative parasite, and referred to the observa- 

 tions of Gage in Bengal, who found that fifty-eight out 

 of sixty five cases of diseased canes were attacked by 

 shot borer {Xi/le/jorus sp.). Later on, Howard contend- 

 ed (Amials 'of Bot., Vol. XVII, No. LXM, March 

 1903) that C. falcatum was the active parasite in rind 

 disease, and that Mehinconiuvi sacchari was a .saprophytic 

 follower of C. falcatum In 1906, important inoculation 

 experiments were conducted by Lewton Brain in Hawaii 

 (Jivl. Dii'. Path, and Plu/s. Ilaicaiuni E.ip. Stat.. No. S), 

 in which he proved that infection could not take place 

 through the cane leaf. Inoculated canes gave a red discol- 

 oration in the entire node, but no white central area after 

 two months. This investigator also observed that there was 

 no extension of the diseased area after twelve months, nor was 

 any white spot produced. These experiments were con- 

 ducted on Caledonian variety. The chief damage was shown 

 to be caused by the secretion of invertase by the fungus, 

 thus increasing the glucose ratio. The same author con- 

 cluded that the disease might be perpetuated by the planting 

 of infected cuttings. 



About the same time, Butler, in India, pointed out 

 (Mem. Dep. Am:, India, Vol. I, No. 3, July 1906) that 

 C. falcatum was associated there with moth borer. Bourbon 

 variety was particularly susceptible to the disease. It was 

 concluded by this author that the disease was carried by sets 

 or cuttings. Maublanc and Delacroix, writing in A<ir. Prat. 

 des Pays Chauds, No 90, 1910, described C. falcatum as 

 a wound parasite which might ari.se from infected cuttings. 

 In 1911, Kulkarni, in India, stated (y^'u/. Dep. Afjr , Bombay, 

 No. 44), that his experiments showed that infection by plant- 

 ing diseased sets was by far the commonest form of commu- 

 nication. Slab experiments failed to prove infection in 

 moth borer holes. During the same year Butler reported 

 (Ann. Report Agr. Stat., East Bengal and Assam, 1911) that 

 the West Indian canes B.147, B.17.53, B.376 had been 

 found to be resistant to red rot in India, but B. 208 was 

 found to be susceptible; 



Early in 1912, the subject received considerable atten- 

 tion by American workers. Edgerton's results (.Vod. Suff. 

 Plant., Jan. 27, 1912) entirely negatived infection from 

 diseased cuttings. Leaf trace infection was considered 

 possible but unlikely. This investigator worked with Purple 

 and Striped Californian varieties, and with D.7.5 and D 9.5. 

 The Californian canes were found to be more susceptible 

 than the Demerara ones. In the case of the inoculations on 

 the former, the disease spread through two to five joints 

 during the season, whereas in the case of the Demerara 

 cuttings the disease spread during the .same period through 

 only one to two joints. The largest number of infections in 

 a diseased field were attributed to Diatraea saccharalis. Of 

 the canes attacked by this borer 50 per cent, contained 

 C falcatnm. 



More recently Johnston, in Porto Rico, emphasized 

 (Sec. Ann. Report E;qi. Stat. Swi. Prod. Assoc., Porto 

 Rico) the close relationship between C. falcatum and climatic 

 conditions and presence of moth borer respectively. This 

 author observed that under-ripe canes were more resis- 

 tant than over-ripe. The disease was noticed to be very 

 severe on mature D.625 canes free from moth borer, 

 also on over-ripe Otaheite suffering from drought and on 

 canes badly infested with moth borer. It was considered 

 probable that C.ta'.catum on leaf sheaths might kill the 

 leaves, but not infect the cane. Bordeaux mixture was 

 found to be useful as a preventive of infection of cuttings 

 during germination under conditions of drought. 



During the same year (1912) South and Dunlop 

 observed C. Jalcatuiu on B.147, hitherto a very resistant 

 variety, in St. Kitts. The dise;ise was chiefly prevalent in 

 fields where this variety had been grown continuously for 

 some years. Conditions of drought had also prevailed and 

 moth borer and shot borer were present in large numbers. 

 Ballou was of opinion that the shot borer did not attack canes 

 free from C falcatum. He considered it probable that the 

 insects were attractei| by the smell of the fermentation set 

 up by the fungus. 



Quite recently, in British Guiana, Harrison and 

 Stockdale (We.';! Ind. Bull., XIII, No. 2) have empha- 

 sized the fact that in every variety of sugar-cane there is 

 a tendency towards running out, which may be partly the 

 cause, or partly the effect of the prevalence of red rot disease. 

 These investigators have pointed out the fact that the older 

 ratoons of I).62.'') (the seedling itself being moderately resis- 

 tant) are as susceptible to disea.se as D.4399 and I) 4407 

 which are seedlings of, and resemble in susceptibility, the 

 Bourbon cane. 



From the references that have been given above it will 

 be seen that the position in regard to the parasitology of 



