THE HUMID GANGRENE OR POLVILLO OF SUGAR-CANE IN ARGENTINA. 



In 1895 Spegazzini, of La Plata, described a wet gangrene of the sugar-cane from the 

 province of Tucuman (lat. 26 to 28 south) in Argentina. In the first part of his paper he 

 runs over briefly all the various diseases of sugar-cane which he has met with, and states that 

 the wet gangrene or Polvillo, as it is frequently called by the farmers, is the most serious 

 disease of cane in Argentina. The loss was so great in 1893-1894 that he paid a visit to the 

 province and made a special study of the disease. He states that after a considerable search 

 through literature he was unable to identify this disease with any other, unless it be a disease 

 of cane in Java and Mauritius, which he found briefly described in some publication. In his 

 opinion the disease is very old, its recent rapid development in Argentina being due to defec- 

 tive methods of cane-planters. In many respects his account of the disease suggests Cobb's 

 disease of sugar-cane. The particulars in which it approaches this disease are the following: 



The chlorotic aspect of the plants ; the leaves lose some of their rigidity and luster, and 

 bend down as if withered. On these plants certain leaf -blades bear long dead stripes, 

 involving the entire thickness of the leaf tissue. These stripes are more abundant on the 

 lower half of the leaf-blade, seldom reaching more than half the length of the blade. They 

 are linear, narrow, of variable length, vivid red or more rarely violet or orange-colored. The 

 same stripes appear on the leaf-sheath, especially on the inside of the sheath. Theinnerface 

 of these leaf -sheaths also bears numerous small red spots and a gummy exudate with a repug- 

 nant odor. Such leaf-sheaths are said to be thicker than normal, rigid, fragile, breaking 

 easily. The terminal bud is much inclined to rot and it comes out easily with a gentle pull 

 from the leaf-sheaths which envelop it, and then its basal part is found to be decomposed and 

 yellowish or reddish, gummy, viscous, and transformed into a purulent paste with a strong 

 odor, said to be like that of rotten leather or butyric acid or ammonium sulphide. When 

 such cane plants are divided longitudinally it is observed that the terminal bud is entirely or 

 partially decayed, together with a variable number of the leaves surrounding it. This decay 

 also sometimes extends downward through the central part of the mature cane stem, excep- 

 tionally even to the root. The red stain, which becomes more pronounced on contact with 

 the air, is more abundant in the nodes at the level of the leaf-sheaths and on cross-section of 

 the fibro-vascular bundles. The terminal bud, even when not diseased, may be wrapped 

 about and compressed and prevented from expanding properly by the diseased leaf-sheaths 

 surrounding it; in other words, it is imprisoned and suffocated or strangulated by these 

 gummy surrounding leaves (see Cobb's disease, p. 16). Sprouts often rise from the base of 

 such affected canes or from the canes themselves, but more often the latter are killed out- 

 right. Canes which appear healthy on the surface may be diseased within. 



Spegazzini carefully considers the effect of soil, rainfall, temperature, and other local 

 conditions, and reaches the conclusion that while some of them may favor the disease none 

 of them are responsible for it. He also considers agricultural methods and states that at 

 first many of the cane planters were inclined to believe that plant-cane was more subject to 

 the disease than ratoon-cane, and he himself arrives at the conclusion that this was true 

 formerly, but that now the disease is widely distributed on the cane, no matter what the 

 treatment has been. He thinks beyond any reasonable doubt that the disease has been 

 propagated extensively by planting diseased canes. 



According to data which I have received it appeared that in the beginning the plant-cane exclu- 

 sively was attacked by the gangrene, and on arriving at Tucuman there was much to bear out this 

 idea. However, others declared that even though in the beginning they had held this opinion expe- 

 rience had demonstrated to them the contrary, and they invited me to compare fields of plant-cane 

 with fields of ratoon-cane, which I found equally diseased. With all this, and that which I shall 

 explain later, I believe it is true that the new plantations are, or at least have been, most subject to the 

 invasion of the plague. 



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