8 BULLETIN 562, U. S. DEPARTMENT OF AGRICULTURE. 



ing, so as to avoid breaking the roots; with acid reagents and alka- 

 line reagents ; and with various chemical disinfectants. Considerable 

 difficulty was experienced in maintaining the infection in the cylin- 

 ders, because of their becoming excessively dry or from some other 

 unfavorable condition, so the results were rather inconstant and un- 

 certain. The results of tests covering three years, mixtures of sandy 

 and clay soils being used, seemed to indicate that the wilt organism 

 is not very active in clayey soils, but none of the chemical constituents 

 of clays applied singly to sandy soils appeared to have any decided 

 action on the organism. A rather extensive series of tests was made 

 with acids and alkalis. For the former sulphuric acid, acid potas- 

 sium sulphate, and nitric acid were used, and for the latter quicklime, 

 calcium carbonate, potassium carbonate, sodium silicate, and sodium 

 carbonate were employed. In most cases at least two different rates 

 of application were made. The results of tests covering three years 

 indicate in general that alkalis are favorable to the wilt organism, 

 while acids retard its development, but the results were not very 

 constant and failed to furnish any basis for a practical remedy. De- 

 tails of the tests are shown in part in Table I. Each cylinder should 

 have contained four plants, but it will be noted that the stand was 

 poor, due largely to the toxic action of the chemicals applied to the 

 soil. 



Table I. — Tests of tobacco plants grown in cylinders containing soil treated 

 vsith acids and with alkalis at West Raleigh and Creedmoor, X. C, in 1913 

 and 1914. 



Cylinder Xo. and 

 location of test. 1 



Soil tieatment. 



1913.— Xumber of 

 plants. 



1914.— Xumber of 

 plants. 



Wilted. Healthy. Wilted. 



I 



TIealthv. 



11 and IS 



11 and 13 (Creed- 

 moor). 

 35 and 42. 



Acid potassium sulphate, 17 grams. 

 Acid potassium sulphate, 85 grams. 



Sulphuric acid, 1 ounce in 6 quarts of water 

 Sulphuric acid, 2 ounces in G quarts of 



water. 

 Nitric acid, 2 1 ounce in 6 quarts of water 



Lime carbonate, 600 grams 



Quicklime, 300 grams 



3S and 43 



14 and 21 



4 (Creedmoor) 



10 (Creedmoor), 12 



(Creedmoor). 



17 and 24 



12 and 19 Sodium carbonate, 300 grams 



15 and 22 Sodium silicate, 17 grams 



\ Potassium carbonate, 70 grams 



None. 

 2 



None. 



4 

 1 

 3 



None. 



6 















None. 



Xone. 



1 



3 









4 



1 















1 Te^ts located at West Raleigh, except a^ otherwise stated. 



2 Cylinder Xo. 38 received 4 ounces of nitric acid and cylinder Xo. 43 received no acid in 1914. 



In the cylinder tests with disinfectants, use was made of formalin, 

 potassium permanganate, chlorid of lime, atomic or superfine sul- 

 phur, [i-naphthol, Bordeaux mixture, and a number of proprietary 

 preparations, mostly coal-tar products, many of them in varying 

 rates of application. Xo decidedly beneficial results were obtained. 



