846 EXPERIMENT STATION RECORD. [Vol.43 



form of Illiizoctonia was isolated from the diseased roots, but the relation of 

 thi> fungus to the disease has not been definitely established. 



In connection with the Thielavia root rot, the control of the disease in the 

 seed bed through sterilization is deemed practicable. In the field the question 

 of the relation of the fungus to soil reaction seems to be of importance, and the 

 author claims that by the use of cover crops and acid fertilizer materials the 

 acidity of heavily infected fields has been restored in a remarkably shox't time. 



Some experiments are reported showing the effect of various chemicals when 

 added to the soil for the control of root rot. Formaldehyde was the only sub- 

 stance used that checked the development of root rot to any considerable extent. 

 At the lower concentrations this substance apparently stimulated root growth. 

 Sulphur, mercuric chlorid, and ferrous sulphate reduced root rot to some extent 

 but had an injurious effect on the root development of the plants. 



Laboratory experiments are said to be in progress vpith the Thielavia fungus 

 to determine the specific action of the different acids and bases on the growth 

 and development of the fungus in culture, as well as to determine the limits 

 between which the fungus is actively parasitic. 



Effect of copper soap and of Bordeaux soap spray mixtures on control 

 of tomato leaf spot, F. J. Pbitchard and W. B. Clark {Fliytopathology, 9 

 (1919), No. 12, pp. 55Jf-5GIt, figs. 7). — The authors have undertaken to develop 

 better methods of spraying and cheaper and more effective spraying mixtures 

 for control of tomato leaf spot. A test was made of a number of different 

 fungicides, among them Bordeaux mixture made of different formulas, copper 

 sulphate, copper sulphate and soap, copper oleate, copper stearate, and copper 

 resinate. 



The most promising spraying mixtures were Bordeaux mixture, Bordeaux 

 mixture to which soap was added, and a copper sulphate soap mixture. The 

 copper seap mixture composed of 0.5 lb. copper sulphate, 3 lbs. fish oil soap, and 

 50 gal. of water gave the best results as far as yield is concerned, and it has 

 the additional advantage of being much cheaper than Bordeaux mixture, but it 

 was not quite so effective in control of the disease as Bordeaux mixture to which 

 fish oil soap was added. 



Wilts of the watermelon and related crops, J. J. Taubenhaus (Texas 

 Sta. Bui. 260 (1920), pp. S-50, figs. 17). — A summary is given of the results of 

 investigations on the Fusarium wilts of cucurbits in Texas. The author claims 

 that the Fusarium wilt of watermelon is caused by three distinct species, 



F. niveum, F. citrulli, and F. poolensis. The wilt of squash and cashaw is 

 attributed to a distinct species, F. cucurbitce. The species occurring on the^ 

 watermelon and squash were found unable to attack cotton, okra, cowpea, potato,] 

 tomato, or any otlier plants. 



As a result of his investigations, the author claims that P. niveum of water-l 

 melon is in no way related to F. vasinfectum, which attacks cotton and okraj 

 only, F. malvacearum was found to be a weak parasite of okra, but did not 

 affect the cotton plant. A number of other species of Fusarium are reported' 

 as being limited to specific host plants in Texas. It is stated that a wilt is pro- 

 duced in cucumbers and cantaloup by Bacillus tracheiphiJus, and that a 

 Fusarium is often associated with this wilt but is present only as a secondary 

 Invader. 



For the prevention of the wilt of watermelon the author recommends a three- 

 year rotation accompanied by the planting of immune or resistant varieties. 



Molding of snow smothered nursery stock, C. Habtley, R. G. Pierce, and 



G. G. Hahn (Phytopathology, 9 (1919), No. 11, pp. 521-5S1).— The frequent de- 

 struction by parasites of seedling conifers in nurseries has led to a study of 



