90 



MASS. EXPERIMENT STATION BULLETIN 175. 



mosaic symptoms. It is impossible to make a definite statement on this 

 point, however, as the writer has not been able to gather sufficient 

 data over a series of years to prove or disprove it. 



Fertilization in Relation to Mosaic Disease. 



It has been repeatedly shown by many investigators (see historical 

 summary) that a lack of plant food alone will not suffice to produce the 

 mosaic disease, and the writer has also, in connection with the tomato, 

 shown that an excess of nitrogen, potash, phosphoric acid and lime will 

 not produce nor intensify the disease. ^ 



The same has been found to be true for tobacco. In our experiments 

 on tobacco, the method made use of was to add to each pot the proper 

 amount of a complete tobacco fertilizer (in this case applied at the rate of 

 3,000 pounds per acre), and then to add an additional amount of nitrogen, 

 potash and phosphoric acid in quickly available forms, equal to that 

 already present. No mosaic was produced in any case, although where 

 the amount of nitrogen was trebled a rather pecuUar malformation of the 

 leaves was observed which at first sight might have been mistaken for 

 mosaic sjonptoms. All inoculations failed to take, however, and the 

 trouble therefore could not have been the true mosaic. 



It has been held that liming would lessen the prevalence of the disease, 

 but the writer's observations and experiments do not bear out this state- 

 ment. Under field conditions this may be the case in certain seasons, but 

 continued observations from year to year on heavily limed areas show no 

 appreciable lessening of the number of mosaicked plants. Seedlings and 

 plants grown in the greenhouse in soil kno^AOi to be heavily infected in- 

 dicated the same results, as also did the work on new soil with mosaicked 

 seedlings. Here lime was applied in varying amounts at the rate of from 

 500 to 6,000 pounds per acre. No appreciable effect on the mosaic disease 

 was observable. The results obtained are given in the following tables : — 



Table II. — Effect of Liming on Mosaic. 



[New soil, lime, mosaicked seedlings.] 



Lime (Pounds per Acre). 



New Soil in 



Pots (Number 



planted with 



Mosaicked 



Seedlings). 



Number of 

 Plants show- 

 ing Recovery 

 One Month 

 after Planting. 



500, . 

 1,000, . 

 2,000, . 

 4,000, . 

 6,000, . 

 No lime (check), 



' Twentieth Annual Report, Mass. Agr. Exp. Sta. (1908), p. 140. 



