136 THE POTATO 



etc. In most of these the amounts of arsenical 

 compounds present is small. 



Contact Remedies Standard. Whale Oil Soap, Car- 

 bon Bisulphide, etc. 



While some of the poisons in Group 4 (proprietary) 

 have value, they are too expensive, and the work of 

 various experiment stations shows that Paris green or 

 arsenate of lead are cheaper and generally much 

 more effective poisons. 1 



Paris green rarely occurs on the market pure. In 

 New York the law requires that it contain 50 per cent, 

 of arsenious oxide or white arsenic. Often some of 

 this arsenic is soluble in water, and in such cases it is 

 liable to burn foliage. If more than 4 per cent, of 

 water soluble arsenic is present the sample should be 

 condemned. 



Paris green tends to sink to the bottom of the spray- 

 barrel; hence, unless kept well stirred, the concen- 

 trated solution applied at the last may burn the foliage. 

 It should be applied at the rate of about i pound per 

 acre, in not less than 100 gallons of Bordeaux mixture. 

 When applied dry, mix i pound of Paris green with 

 50 pounds of land plaster, flour, slaked lime, or any 

 other dry powder. 



At (N. Y.) Geneva Experiment Station, in 1904, 

 Paris green was applied to potatoes at the rate of 3 

 pounds per acre in 150 gallons of water. Four appli- 

 cations were made during the season, and no injury to 

 the foliage occurred. The results show that Paris 

 green is of distinct fungicidal value, and that it in- 



Me. Bui. 68, 87, 98. 



