136 EXPERIMENT STATION. [Jan. 



11. Investigations relating to Mosaic Disease. 



II. CHAPMAN. 



The Mosaic Disease of Tomato and Tobacco. 



Work on this disease was taken up for the first time at the 

 station in July, 1907 ; too late in the season to observe the 

 seed beds and the transplanting of field-grown tobacco in its 

 natural state. However, the work of the past year has been 

 more in the nature of verifying the results obtained by other 

 investigators than in research purely, so only a preliminary 

 report can be made at the present time. 



The disease occurs on several plants, but seems to be most 

 injurious to tobacco, although it has been found that in the 

 case of greenhouse-grown tomatoes a heavy pruning back will 

 bring on the disease, and, as observed at this station, lessens 

 production. 



All investigators agree that the mosaic disease is a purely 

 physiological one, but there seems to be much doubt as to 

 whether it is infectious or contagious in character, or both. 

 There also seems to be some difference in opinion as to the 

 direct cause of the disease. In tomatoes it is always produced 

 when the vines are heavily pruned, and in the work here it has 

 been shown that it is connected in no way with methods of 

 transplanting the young plants, and only results from subse- 

 quent pruning. 



It has been found that tobacco is much more susceptible 

 under conditions which tend to produce the disease than is the 

 tomato. In the case of tobacco, A. F. Woods J found that when 

 a plant was grown in soil containing small roots of diseased 

 plants the disease always occurred sooner or later. In our 



i Mosaic Disease of Tobacco. A. F. Woods, Bulletin No. 18, Bureau of Plant Industry. 



