1892.] PUBLIC DOCUMENT — No. 33. 235 



impossible to say, since they have apparently caused no loss 

 in this State during the past season, and it has not been 

 possible to obtain material for study. The purpose of the 

 present note is to call the attention of tobacco growers to 

 the fact that the department is desirous of studying the 

 diseases named, and to ask them to notify the writer of the 

 existence of any such in their barns next season. It seems 

 very probable that much can be done towards a better 

 understanding of the nature and means of prevention of 

 these sources of loss. The writer desires here to thank 

 those growers who have so promptly replied to his inquiries, 

 and hopes to be as promptly informed of the existence of 

 opportunities for the study of these diseases. 



Preventive Treatment. 



A somewhat extended account of the principles underlying 

 the preventive treatment of fungous diseases of plants, with 

 detailed directions for the preparation and application of ihe 

 most efficient fungicides, was issued as Bulletin 39 of this 

 station, in April last. That interest in this subject is being 

 awakened was shown by the demand for the bulletin and for 

 further information ; but it is impossible to say to what extent 

 its recommendations were acted upon, as very few persons have 

 communicated to the department any report of such treat- 

 ment or its results. The bulletin named can still be furnished, 

 on request ; but the more important points of the discussion 

 are given below. 



Since a plant which is once fairly attacked by a fungus is 

 lost, treatment must be directed toward preventing the 

 development of fungi upon the plants to be saved. Pro- 

 tective measures may be of two sorts ; those which remove 

 possible sources of infection from the plants, and those which 

 fortify the plants against infection. The latter of these 

 objects is accomplished by the use of fungicides ; the former 

 may be largely accomplished by hygienic treatment. 



There are definite laws of health for plants as well as for 

 animals, and in one case, as in the other, neglect of those 

 laws invites disease. In the first place, plants which are 

 expected to grow and thrive must be furnished with an 

 abundance of the materials necessary to growth. Weak, 



