IGa EXPERIMENT STATION. [Jan. 



tobacco. During the last season, further study was made of the influence of cover-crop- 

 ping and liming on the development and effect of black root-rot, caused bj' Thielavia 

 baHcola, and considerable data were obtained. An important feature of this year's 

 field work was the successful infestation by artificial means of experimental field plots 

 with Thielavia. With permanent plots knowTi to be infested with this fungus and others 

 free from it, valuable results should be obtained in the ne.xt few years. 



Botany Project 4. "Investigations of the methods of controlling lettuce drop." 



Professor Osmun and Assistant Professor Krout. 



The work on this project has been completed. The investigation involved prelimi- 

 nary study of the reaction of the drop fungus, Sclerotinia lihertiana, to various factors 

 and extensive testing of these factors in their relation to the control of the disea.se in the 

 greenhouse. The net practical result is the definite determination that the disease may 

 be controlled with relatively little expense by treating infested soil with formaldehyde. 

 A 1-100 solution applied to the surface of the soil at the rate of one gallon to the square 

 foot was found efficacious. It was found also that treatment must begin in the seed- 

 bed to prevent infection of young plants before transplanting to the main house. De- 

 tails of practice were worked out in some of the commercial houses of the State. 



Botany Project 5. "Experimental spraying for the control of cucumber mildew 

 under glass." 



Assistant Professor Krout. 



Bordeaux gave slightly better results this past season than did a copper-lime dust. 

 Full control, however, is not yet obtained. 



Botany Project 6. "Investigation of onion diseases." 



Professor Osmun and Professor Anderson. 



As stated in the last report, the work on this project has been focused on a study of 

 onion smut and its control. Technical Bulletin No. 4, "Development and Pathogenesis 

 of the Onion Smut Fungus", distributed early in the present year, is a report of some 

 of the more technical features of this work. Field tests of formaldehyde applied at 

 different concentrations and rates were continued this year. In co-operation with the 

 Department of Rural Engineering, the apparatus for applying formaldehyde has been 

 perfected to the extent that errors due to uneven distribution of the fungicide have been 

 eliminated. The development of this equipment renders advisable the continuance of 

 field tests for at least one more season. The use of the new equipment bj^ practical 

 growers gave some ver}^ interesting and significant results. 



Botany Project 9. "Investigation of carrot blight." 



Assistant Professor Krout. 



The work on this project was conducted along the same lines as reported last year. 

 Considerable attention was given to study of the etiology of the disease and it has been 

 definitely established that the pathogene is a Macrosporium. The incubation period 

 has been determined and physiological studies of the organism are iii progress. In the 

 field, considerable benefit was shown from spraying with Bordeaux mixture, but definite 

 conc'lusions can be drawn only from the results of several ^years' work. 



Botany Project 10. "Apple disease control investigations." 



Assistant Professor Krout. 



The work on this project has been confined almost wholly to an investigation of the 

 control of scab. Very satisfactory progress has been made and much of importance to 

 the practical orchardist has resulted. It has been definitely established that the Mcin- 

 tosh apple, which is very susceptible to attack by scab, can be protected against this 

 disease by spraying with fungicides. Results from dusting also have been excellent, 

 Ijut further tests are necessary. The best results have been obtained by the use of a 

 3-10-50 home-made Bordeaux mixture for the pre-pink and pink applications, followed 

 by liquid lime-sulphur, 1-50, for the summer sprays. The most satisfactory results 

 from dusting were obtained with finely ground sulfur. Copper-lime dust proved 



