1918.] DISEASES OF PLANTS. 549 



Potato and tomato diseases, N. J. Giddings (West Virginia Sta. Bui. 165 

 (1911), pp. 2.'f, fiffs. 21). — Descriptions are given of some of the most widely 

 spread and destructive diseases of potatoes and tomatoes, with suggestions for 

 their conrol. 



For the prevention of these diseases, rotation of crops, selection of seed tubers 

 and varieties, removal of diseased material, and thorough spraying with Bor- 

 deaux mixture are recommended. 



In connection with the potato diseases, the author gives an account of an in- 

 vestigation to determine whether potato powdery scab was liable to become a 

 serious menace in West Virginia. Badly diseased potatoes were planted in the 

 field at the West Virginia Station, and at harvest time there was not the least 

 sign of the disease on any of the tubers. This is believed to indicate that the 

 southern conditions are unfavorable to powdery scab. 



A summary is given of spraying experiments for the prevention of potato 

 diseases, from which it appears, as a result of six years' work, that plats 

 sprayed with 5 : 5 : 50 Bordeaux mixture gave increased yields of from 11 to 53.5 

 per cent. These experiments were conducted on a commercial scale and are 

 believed to indicate the value of spraying even in seasons when neither early 

 nor late blight was prevalent. Tests of commercial lime sulphur, which is some- 

 times recommended as a potato spray, gave results indicating that this material 

 is not to be reconnnended for us(' on potatoes. 



Our present knowledge of potato diseases: What they are and how to con- 

 trol them, H. A. Edson {Proc. Potato Assoc. Amer., 3 {1916), pp. 52-56).— The 

 author gives a discussion of potato diseases, more particularly in the United 

 States, including a leaf-bronzing trouble, now becoming prominent, which 

 appears to be primarily of the malnutrition type, streak, mosaic, late blight 

 (Phytophtliora infestans) , powdery scab, several diseases induced by Fusarium 

 spp., blackleg, black scurf (Rhizoctonia), curly dwarf, and leaf roll. 



It is thought that, aside from the specific measures mentioned in connection 

 with these diseases, the most practical method for combating potato disea.ses 

 is probably that of planting the best stock available in the best soil types, 

 cultivating in the best manner, frequent roguing out of all undesirable plants, 

 and careful selection of seed tubers. 



Potato mildew or late blight, H. Bocher (Vie Ayr. et Rurale, 1 (1911), No. 

 21, pp. 369, 310). — This is a brief account of the manifestations, attacks, preva- 

 lence, effects, and control of Phytoplithora infestans on potatoes. 



The organism is said to require temperatures between 20 and 80° C. (6S and 

 86° P.) and to be controllable by means of two or three treatments of the 

 potato plants with Bordeaux mixture, the first to be applied before the plants 

 have bloomed, in May or June, the second, 20 days later. A third may profit- 

 ably be given in August, if applied very promptly on recognition of its neces- 

 sity. Seed treatments are also discussed, including the use of copper sulphate 

 and that of sulphuric acid. Some resistant varieties are named. 



[The so-called Lahaina disease and other diseases of sugar cane], H. P. 

 Agee (Proc. Hawaii. Sugar Planters' Assoc., 36 (1916), pp. 18-20). — It is stated 

 that soil studies by Burgess continue to point to a correlation between the occur- 

 rence of black alkali and the failure of the cane variety known as Lahaina, 

 which, though vigorous, gives way under various unfavorable environments. 

 Tests following out this theory by treating the soil with gypsum or with green 

 manure have not proved conclusive. 



Infectious top rot is reported by Lyon to have appeared on Oahu and Maui 

 during the year, though apparently confined to Kauai for the previous eight 

 years. This disease, which is considered dangerous, was arrested by cutting 

 and burning the affected canes. 



