846 EXPERIMENT STATION RECORP. 



usual custom of plauting the seed iu a lull and subsequent ly thinning to one 

 plant was followed in order to prevent the introduction of diseases from the 

 Beed bed. 



As a result of the experiments it appears that the use of lime is distinctly 

 beneficial in combating club root disease in the field, but that acid phosphate 

 is of little effect. Stable manure brings about conditions that are .decidedly 

 favorable for the spread of the disease. 



The author recommends for the control of club root special effort to prevent 

 the introduction of the disease into noninfected fields; the practice of crop 

 rotations which will allow at least 3 years between crops of cabbage, ruta- 

 bagas, or turnips; and limiting tlie application of stable manure or acid phos- 

 phate to the crop which precedes cabbage. Lime should be applied at the rate 

 of 100 bu. or more per acre 1 or 2 years before planting the cabbage. 



On the curly leaf disease of cotton, G. Kranzlin (Pflanzer, 7 (1911), No 6, 

 pp. 327-329, pis. 4)- — fhe author reports the results of further investigations on 

 this subject (E. S. R., 25. p. 652), iu which experiments on the cause of the 

 curly leaf of cotton indicate that the disease is caused by leaf hoppers (cicads). 



A serious lettuce disease, F. L. Stevens (North Carolina Sta. Bui. 217, pp. 

 21, figs. 8). — Continuing work previously noted (E. S. R., 25, p. 548), the author 

 describes a disease of lettuce due to Sclerotinia libcrtiana, which is Icnown to 

 occur over a considerable portion of the eastern part of the United States. In 

 some regions it has been reported as being severely epidemic, losses of from 10 

 to 70 per cent being reported in various parts of North Carolina. 



The disease is said to appear sometimes the first season the crop is grown in 

 a given soil, but usually not until sevei*al crops have been raised. A study of 

 the fungus showed that the spores are comparatively short-lived. The sclerotia 

 are long-lived and are the only resting stage adapted to perpetuate the fungus. 



Various methods of control have been tested. These include soil disinfection 

 by heat or by chemical solutions, mulching, etc., but in the experiments con- 

 ducted by the author in commercial beds none seemed very satisfactory. An 

 experiment was then undertaken in which lettuce beds were thoroughly inocu- 

 lated with sclerotia and seeded to lettuce. The beds were examined and as 

 soon as a diseased plant appeared it was removed and the ground about it 

 drenched with Bordeaux mixture or a solution of copper sulphate. 



As a result of his investigations the author thinks that the disease may be 

 controlled by a careful inspection of lettuce beds every other day and pulling 

 up and burning all diseased plants. The place in the bed from which the plants 

 are removed should be drenched with Bordeaux mixture or sulphate of copper 

 solution, and the inspection continued throughout the season. The next year 

 the same treatment should be followed, and it is thought probable that two 

 years of this treatment will almost, if not entirely, eradicate the disease. 



Heterosporium variabile, its relation to Spinacia oleracea and environ- 

 mental factors, H. S. Reed and J. S. Cooley ( Virginia Sta. Bpts. 1909-10, pp. 

 78-99, figs. 10). — This is a detailed account of investigations a preliminary note 

 on which has been given elsewhere (E. S. R., 23, p. 350). 



The authors, summarizing their investigations, state that the disease of 

 spinach popularly known as rust is caused by the fungus H. variabile, and 

 their investigations show that it is a weak parasite and usually infects spinach 

 plants that have been injured or weakened by other agents. Peronospora 

 effusa, a parasite of the spinach, appears to be a forerunner of the rust, and 

 winter injury is another predisposing factor to the appearance of Heterospo- 

 rium. Considerable variability in the form and habit of the fungus is noted, 

 and in cultures it first grows poorly as a saprophyte and afterwards, changing 

 its form and habit, grows luxuriantly. 



