1917] DISEASES OF PLANTS. 847 



On the part played by the seed in the dissemination of potato diseases and 

 on the advantages of disinfecting with corrosive sublimate, H. M. Quan- 

 JEB (Meded. Rijks Hoogere Land, Tuin en Boschboutcsch. [Wageningen], 9 

 (1916), No. 2-4, pp. 94-126, pi. 1). — This is the second contribution to a mono- 

 graph on potato disease in Holland (E. S. R., 29, p. 347). The quarantine meas- 

 ures employed in the United States are said to have made it necessary to study 

 closely the so-called scab diseases from the standpoint of their distribution and 

 control in Holland. 



Common scab (Actinomyces scabies) is said to be present in many parts of 

 that country, the fungus being visible for only a little while just after digging 

 as a gray film on the scab spots. In cases where spraying with Bordeaux mix- 

 ture has retarded the ripening process, the scab spots are deeper and more 

 numerous than when the potatoes are ripened and dug earlier. Powdery scab 

 (Spongospora subterranea) , though not so widely distributed, is present in many 

 parts of the Netherlands. The canker form is not known in that country. 

 Hypochnus solani (Rhizoctonia solani) is very common on the tubers, by which 

 it can be transmitted. 



Experiments were made testing the protective value for each phase of scab 

 of a 1 : 1,500 corrosive sublimate solution on low clay land not infected, on high 

 sandy soil infected with A. scabies and R. solani, and a peaty soil infected with 

 all three diseases, the tabulated results showing the yield of infected or sound 

 tubers and the increase in market value by treatment. It is thought that a 

 1: 1,000 corrosive sublimate solution Is preferable (see also below). 



On the nature, mode of dissemination, and control of phloem necrosis (leaf 

 roll) and related diseases, H. M. Quanjeb, H. A. A. van der Leik, and J. O. 

 BoTJES (Meded. Rijks Hoogere Land, Tuin en Boschboutcsch. [Wageningen], 

 10 (1916), pp. 1-162, pis. 12; abs. in Gard. Chron., S. ser., 60 (1916), No. 1550, 

 p. 124). This is the third contribution of the series noted above. It deals with 

 the external and the histological features, and the pseudo-hereditary character 

 of leaf roll and with metabolism in the plants affected therewith, ^he causa- 

 tion, communicability, external influences, prevention, and notes on diseases 

 related to or comparable with leaf roll of potato or other plants, such as potato 

 mosaic and curly dwarf, yellow stripe and sereh of sugar cane, leaf curl of 

 peanut (Arachis hypogoea), curly top and mosaic of sugar beet, and cases of 

 infectious chlorosis in various plants. 



The phloem in affected plants shows characteristic changes, which are de- 

 scribed and which are summed up in the term necrosis. Apparently it is trans- 

 mitted by the mother tubers, by grafting sound on affected plants, and vice 

 versa, and it passes into the soil, which remains capable of infecting potato 

 plants for at least two years. Varieties differ in suceptibility. The infecting 

 organism has not yet been discovered and may be ultramicroscopic. The disease 

 is apparently not due primarily to the condition of the plant. 



Report of potato spraying experiments for 1915, H. C. Lint (New Jersey 

 Stas. Rpt. 1915, pp. S81-S94, pi. 1). — Results of cooperative experiments with 

 various fungicides and insecticides for the control of potato diseases and insect 

 pests are given which show that Bordeaux mixture applied to an early crop of 

 potatoes increases the yield. Basing his conclusions on three years* experiments, 

 the author considers that climatic conditions play an Important r61e in deciding 

 to what extent the benefits from Bordeaux mixture will be realized. Both 

 homemade and commercial preparations of Bordeaux mixture were found to 

 prolong the life of the vines and to give an average increase of about 45 bu. 

 per acre when applied to second crop potatoes. Early blight is said to have 

 been very prevalent in the plats of the second crop experiment, and it is prob- 

 able that the control of this disease may account for much of the Increase In 



