NOTES AND ABSTRACTS. 



383 



produce a wilt disease affecting the plant as a whole as well as the pink 

 rot of the tuber. This disease has been shown to be contracted directly from the 

 soil. — F. J. C. 



Potato, Leaf-roll, Disease. By J. G. Grossenbacher (Phytopathology, v. June 

 1915, pp. 157-160). — Reviews and approves Quanger's investigation on the 

 death of the phloem in cases of potato leaf-roll. — F. J. C. 



Potato, Leaf-roll Diseases. By O. Appel (Phytopathology, v. June 191 5, pp. 

 139-148). — Leaf-roll is due to interference with the water supply, brought 

 about by various causes. Curly dwarf is characterized by shortened internodes 

 and curly leaves due to the shortening of the midribs ; the stems are brittle 

 and the leaves often remain small; the yield is small, and the tubers produce 

 diseased plants. Streak is somewhat similar, but is characterized by black 

 streaks on the stems and leaf veins, and frequently by black spots on the leaves ; 

 it is supposed to be of bacterial origin but its real cause remains to be discovered. 

 Leaf-roll is characterized by the upward and inward rolling of the potato leaves 

 without undulation of the leaf -margin ; the leaves are usually discoloured, 

 yellowish green, reddish, or even violet, the intensity of the discoloration 

 depending upon the weather ; the haulms are shorter and more erect, the flowers, 

 leaves, and berries are smaller than normal ; the yield is usually small, and the 

 tubers produce diseased plants ; the tubers rarely decay ; the phloem is diseased 

 and enzyme action slow ; the cause is unknown, though it is intensified by certain 

 climatic conditions. Parasitic leaf -roll disease (or vascular mycosis) is due to 

 the attack of species of Fus avium oxyspovum or other Fusavium, or of Verti- 

 cillium alboatvum ; it is distinguished from the non-parasitic leaf -roll diseases 

 by the top leaves withering first, and by the presence of brown spots in the 

 vascular bundles and mycelium in the tissues ; the tubers do not all become 

 infected. Bacterial ring-disease is also sometimes characterized by leaf -rolling ; 

 it is due to Bacterium sepedonicum ; the spiral vessels are filled with the bacteria 

 which secrete enzymes which dissolve the walls and produce cavities ; the 

 pitted vessels are free from them ; the disease is most marked in dry seasons 

 when the leaves begin to die from the edge inwards. Foot disease may be due 

 either to Rhizoctonia solani when the progress of the disease is slow or to various 

 bacteria which soften and often quickly blacken the stem at the point of attack, as 

 Bacterium phytophthorum, B . atrosepticum, B. solanisaprum, and B. xanthochlorum. 



The following table is given to differentiate the diseases : — 



I. Crisp leaves : 



1. Curly dwarf disease. 



II, Rolled leaves : 



1. Non -parasitic : 



A. Leaf-roll disease. 



2. Parasitic : 



A. Vascular diseases : 



a. Fungi — Wilt disease, 



b. Bacteria — Ring disease. 



B. Foot diseases : 



a. Fungi — Rhizoctonia disease. 



b. Bacteria — Black-leg. — F. J. C„ 



Potato Spraying (Queensland Agr. Jour. Sept. 191 4, pp. 233-239). — 

 Requires to the acre about 16 lb. quicklime and 12 lb. copper sulphate for each 

 spraying; the latter costs about 32s. per cwt. — C. H. H. 



Potatos, Curly-Dwarf, Oxidases in. By H. H. Bungel (jour. Agr. Res. ii. Aug. 

 1914, pp. 373-404). — The author, using the method of oxidase measurement 

 he had devised, finds the oxidase activity of normal potato foliage greatest in 

 its youth, after which it falls off, to rise again about the time the plant ceases 

 to grow. Curly-dwarf potatos show greater oxidase activity than normal 

 healthy ones both in the juice of their tubers and in that of their foliage. — F. J. C. 



Potatos, The Spindling-Sprout Disease of. By F. C. Stewart and F. A. Sirrine 

 (U.S.A. Agr. Exp. Stn., New York, Bull. 399, March 1915, pp. 133-143; 

 3 plates). — In 1914 numerous small weak potato plants with very slender stems 

 were noticed on Long Island. On investigation, these weak plants had developed 

 from tubers which had produced slender thread-like sprouts. It was thought 

 that it was due to the weakened conditions of the seed tubers. The name 

 " Spindling-Sprout " is suggested for this disease, the cause of which is not 

 definitely known, though, no doubt, drought and excessive heat are factors in 



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