1913.1 PUBLIC DOCLMEXT — No. 31. 41 



^^ MOSAIC" AND ALLIED DISEASES, WITH 

 ESPECIAL REFERENCE TO TOBACCO AND 

 TOMATOES. 



G. ir. CHAPMAN. 



Tliis disease, or forms of it, has been known for several years, 

 and various articles and papers have been prepared dealing with 

 its description, causes, effects and methods of treatment ; but 

 the results obtained have been so varied that one hardly knows 

 what to conclude. One authority states positively that the 

 disease is contagious, another that it is infectious and still 

 others that it is neither. It is our object in this paper to review 

 in brief the results of other investigators and also the results 

 of several years' work on our part devoted to the study of so- 

 called mosaic disease and physiological troubles which we be- 

 lieve to be more or less closely allied to it. 



This disease is commercially important to the lajTuan only 

 as it affects tobacco, and to a less extent greenhouse tomatoes 

 (we have never found this disease produced on field-grown 

 tomatoes except under artificial conditions of growth), which 

 seem to be less susceptible than other plants of the Solaniacese. 

 It is very important in some localities as regards tobacco, how- 

 ever, because a leaf attacked by it loses its elasticity, and after 

 curing will not make a good wrapper for cigars. The results 

 obtained and presented in this paper will deal simply with its 

 causes, probable methods of control, etc., as regards the practical 

 grower, but not with the physiology and chemistry of the dis- 

 ease from a technical viewpoint. We do not mean to imply that 

 we have said the last word on the subject, but we have made an 

 earnest endeavor to clear up as many points as possible regard- 

 ing this peculiar disease. 



We believe that several other diseases, such as peach " yel- 

 lows," aster "yellows" and others, are more or less similar 

 in character to the true " mosaic," but this paper will treat 



