DISKASICS OF VARIOUS CROPS IO39 



fungus in turn utilises these hollowed out parts to penetrate downwards. 

 This double attack often kills the tree, and the injury tluis occasioned, 

 especially in lo tc 12 year old plantations, is at times very great. 



Means of control : i) cut off the diseased parts unsparingly and tar 

 the wound ; 2) dig out and destroy old stumps, which are more often than 

 net a source of propagation cf the disease. 



813 -Fungoid Diseases of the Sugarcane at Tucuman (Argentina). — ch.wanneju.vn,j. 



in Ministerio de As.ricoltura dc la Nacion, Dircccion General de Enseiianza e InvestigacioiKS 

 Ai^ricolas, Seccion Escuelas Especiales, Year 1916, No. 51, pp. 5-32, 2 PI. Buenos-Aj-res 

 1916. 



A list and description of the fungoid diseases which attack the sugarcane 

 at Tucuman. 



i) " Polvillo " or " gangrena humeda ". — According to the writer, 

 this disease is identical with the " top-rot " ("pokkahbong "), alread}^ dis- 

 covered and studied without nmch result up to now in various sugar- 

 growing countries (Java, Mauritius, Demerara, etc.). The infected plants 

 can at once be detected by their chlorotic appearance; the leaves lose their 

 gloss and rigidity, the apex droops, the tops of the canes show marked 

 signs of disease which increase and spread downwards along the stalk. The 

 infection spreads from without inwards, and from the young to the older 

 portions of the plant. It attacks the base of the leaves, blocks up the veins 

 and thus prevents circulation of the lymph elaborated in the leaf substance. 

 The infected sheaths become leathery and stiif, thereby hindering the growth 

 of the stalk. Although the pathological evidence as a whole points very strong- 

 ly to a bacterial cause, the almost constant presence of larvae or other small 

 organisms in the infected tissues suggests that these animal parasites may 

 play an important part in the growth and spread of the disease. The lar- 

 vae met with most frequently are those of diptera almost all belongiiig to 

 two species, namely : Eiixcsta chavannei (1) and E. argentina Brethes. If 

 larvae of these diptera taken from diseased plants are introduced into a deep 

 wound produced artificially in the region of the terminal bud, the charac- 

 teristic symptoms of " pclvillc " will eventually occur. Anumber of lengthy 

 experiments in field and laboratory were carried out in order to discover 

 the cause of this disease. It is contended that there is no specific bac- 

 terium of the disease, or obligate parasite the action of which is alone suffi- 

 cient to rot the crown of the cane, but that it is due to decomposition pro- 

 diiced by various micro-organisms not yet determined, which penetrate the 

 plart through lesions caused by insects or other agencies. 



It is hsrdlj' possible to ascertain accurately' the origin of tliis disease 

 in the Tucuman plantations, the data available only relating to those years 

 when, as in 1893-1894, "pohnllo" attained large proportions and wrought 

 considerable havoc. The cultivated sugar cane varieties are not all equaly 

 liable. vSome kinds brought from Java ("P. O. Java 36 " and " P.O. Java 

 213 ") as also "Cayana Roxa ", " Verde de las Antillas ",and "Sin Nombre" 

 are distinguished by a high degree of resistance. 



(i) See B. Nov. 1914, No. 1079. (Eri). 



