No. 6. DEPARTMENT OF AGRICULTURE. 759 



potato scab, the fungicidal properties of a considerable uurnber of 

 substances liave been tested during the paet six years. 



"Lime, gas-lime, kainit, corrosive sublimate, sulphur, Bordeaux, 

 cupram, oxalic acid, sulphate and sulphide of ammonium, bisulphide 

 of carbon, sulphuric acid, kerosene, formalin, creolin and benzine 

 have each been added to the soil, and nearly all have had no eifect 

 upon the scab. A few reduced the disease somewhat, as corrosive 

 sublimate, Bordeaux and cupram, but not enough to render them of 

 practical value. Lime increased the percentage of scab. 



"Of the whole list, sulphur only has yielded results which warrant 

 it being recommended to potato growers as a preventive of scab. It 

 is not uniformly active, depending, probably, upon the conditions 

 of soil temperature and moisture. 



"For practical use, ;iUU pounds applied to the open row are deemed 

 sufficient. It is also best to roll in sulphur the freshly-cut 'seed,' 

 as it prevents rapid drying out of the water. 



"The soakiiig of scabbed potatoes in corrosive sublimate has not 

 proved of much practical value when they were planted under the 

 conditions of the experiment, namely, in badly scab-infested soil. 



"Uuinfested soil may be readily contaminated by the introduction 

 of scabbed potatoes or beets. The germ of potato scab, while not 

 readily destroyed by boiling, seems to be largely destroyed by pass- 

 ing through the digestive tract of cattle. Special exposure (ridging) 

 of scab-infested soil to the elements during the winter months dtoes 

 not appreciably ali'ect the vitality of the disease. Susceptibility to 

 scab is greater in some varieties of potatoes than in others. 



"No plants, save the potato and beet (aijd probably the radish and 

 turnip), have been found subject to root scab. Ail attempts to in- 

 oculate various species, both wild and cultivated, many of them 

 closely related to the above-named hosts, have proved unsuccessful. 



"Experiments have demonstrated that the scab fungus is actively 

 retained in the soil for at least six years without the presence of 

 potatoes or beets." 



In connection with the above, I ask that a close reading be given 

 the following summary of Bulletin No. 40, of the Rhode Island Sta- 

 tion, believing that the results stated make plain much truth about 

 this fungous disease: 



"The results from the use of sodium compounds and oxalic acid 

 in connection with barnyard manure confirm those obtained in 1895, 

 viz., common salt (sodium chlorid) tends to lessen the amount of 

 scab. Soda ash (sodium carbonate) tends to increase the scab. Ox- 

 alic acid tends to lessen the scab when used with barnyard manure 

 only or when common salt or soda ash is present. 



"2. A scabless product was produced where calcium chlorid or land 



