30 



MASS. EXPERIMENT STATION BULLETIN 195. 



It will be noted that the onh* substances which did not have an inhibiting 

 action on the growth were formaldehyde, sulfuric acid, and copper sulfate. 

 The rest of the chemicals applied did inhibit the growth of the tobacco, at 

 least in the amoiuits applied. 



A careful examination of the root systems of the plants in the different 

 plots was made by Mr. Krout of this department, who was in direct 

 charge of the root-rot work, and he reported as follows : — 



Table VII. — Comparison of Treatment ivith Thielavia Infection and Root 



Development. 



Chemical. 



Application 

 (Pounds 

 per Acre). 



Thielavia 

 Infection 

 (Check In- 

 fection =100). 



Root 

 Development 

 (Check = 100). 



Formaldehyde, 

 Sulfuric acid, . 

 Sulfur, . 



Mercuric chloride, 

 Copper sulfate, 

 Ferrous sulfate, 



Potassium permanganate, 

 "By-product A," 



4,800 

 2 400 

 1,200 



1,200 

 600 

 300 



2,000 

 1,500 

 1,000 



100 



400 

 200 

 100 



1,000 

 500 

 250 



300 

 100 

 50 



4,000 

 2,000 

 1,000 



Oi- 

 ls 

 15 



75 



85 

 90 



90 

 90 

 100 



90 

 60 

 95 



100 



S8 

 90 



100 

 150 

 125 



75 

 103 

 125 



38 

 65 

 90 



123 

 108 

 108 



70 

 95 

 115 



100 

 100 

 100 



93 

 105 

 95 



From the above it may be seen that the onh' substance used which 

 checked the development of the root-rot, or controlled it to any great 

 extent, was the formaldehyde. The root growth also was apparently 

 stimulated by the lower concentrations. Sulfur, mercuric chloride, and 

 ferrous sulfate, while reducing the root-rot to some extent, had an injurious 

 effect on root development. The copper sulfate and sulfuric acid reduced 

 the amount of root-rot infection somewhat, and did not apparently, except 

 in the case of the greatest strength of sulfuric acid, reduce the root develop- 

 ment to any extent. 



These experiments were continued in the following year with comparable 

 results. It would seem that none of the substances used, with the excep- 

 tion of formaldehyde, were sufficiently beneficial in their action to warrant 



