48 EXPERIMENT STATION RECORD. [Vol.35 



Temperature and relative humidity were found to influence production of 

 conidia and infection in much the same way. A temperature of from 80 to 90°, 

 with a night minimum preferably not below 60°, was most favorable to conidial 

 production, which was checked by a temperature of 100° or higher and retarded 

 by a range from below 50 to 80°. A maximum humidity ranging above 60 

 for not less than 15 to 18 hours each day induced a good growth of the fungus. 

 Because of the higher humidity on the lower than on the upper surface of the 

 leaf, the conidia are generally more abundant on the lower surface of the spots, 

 and because of the action of rain and wind they disappear more rapidly from 

 the upper surface. 



Control of club root of crucifers, P. Burkhardt {Mdllcr's Dcut. Gart. Ztg., 

 30 (1915), No. 3ft, pp. 214, 275, fig. 1). — Control measures recommended for 

 Plasmodiophora brassicw, causing club root of crucifers, include rotation, the 

 application of 500 gm. of freshly slaked lime per square meter in the fall, fol- 

 lowed in the spring by 50 gm. of a potassium salt with well rotted compost, 

 careful selection of stock for planting, and removal of any unthrifty plants. 



Flax disease investigations (North Dakota Sta. Rpt. 1915, pt. 1, p. 16). — The 

 investigations in flax diseases, which have been in progress for some time, are 

 briefly described. Special centgener plantings have been made to increase re- 

 sistance of flax to rust and wilt. 



The I'esults for the year covered by this report are said to indicate that 

 resistance can be developed to an extent that will practically control these 

 diseases. Trials were made of seeds sent in by farmers to be tested for 

 resistance, the results of which seem to indicate that resistance power, when 

 once acquired, will endure for a considerable period, even though the crop 

 is grown on groiind free from the diseases. Crops grown from seed which 

 had been wet, moldy, or frozen showed diminished powers of resistance. 



A Rhizoctonia disease of licorice, W. IIimmelbaub (Ztschr. Lanclio. 

 Versuchsio. Osterr., 11 (19U), No. 8-9, pp. 671-683, figs. 9). — Giving the results 

 of microscopic and microchemical studies on a Rhizoctonia disease said to 

 decrease materially the returns from Glycyrrhiza, the author describes the 

 development of the fungus and of the alterations caused thereby. It is stated 

 that the diseased portion soon takes on somewhat the character of a foreign 

 body, having been separated more or less completely by a cork layer from 

 the healthy portions. 



Investigations of potato diseases (North Dakota Sta. Rpt. 1915, pt. 1, pp. 

 17, 18). — It is reported that the Fusarium wilt, Fusarium rot, brown stem rot, 

 Rhizoctonia, and leaf roll of potatoes are of economic importance in the potato 

 districts of North Dakota. These diseases appear to be more active in the 

 lighter soil areas, while early blight is reported as occurring extensively in the 

 region of heavier soils. 



The frequent occurrence of Rhizoctonia on potato vines has led to a study 

 of that organism. In samples of soil collected froiu 24 plats that had been 

 devoted to crop rotation for 24 years, 18 lots showed the presence of Corticium 

 vagum. Many of these plats had not been cropped to potatoes for many years. 

 As a result of the investigation it is considered probable that Rhizoctonia occurs 

 on the roots and debris of a large variety of plants, and that the present 

 method of treating seed potatoes to avoid this disease is correspondingly futile. 



Potato diseases, O. Schlumberger (Deut. Landw. Presse, 42 (1915), No. 41, 

 pp. 369, 370, pi. i).— This includes a description of Phytophthora tuber rot, 

 bacterial wet rot, Fusarium or dry tuber rot, verticilliose or wilting disease, 

 bacterial ring rot, hollow tubers, various spotting diseases, Oospora scab, 

 Spongospora powdery scab, canker (Chrysophlyctis endoMotica), and Rhi- 

 zoctonia disease. Some preventive and remedial measures are also discussed. 



