38 BULLETIN 278, U. S. DEPARTMENT OF AGRICULTURE. 



marketable fruit. Plat III (KOH, 11 pounds, and sulphur, 12.5 

 pounds), 83.352 per cent, No. 2 commercial sodium sulphid 80.833 

 per cent, and the unsprayed plats averaged but 60.793 per cent of 

 marketable fruit. 



Experiment XXI. 



FIELD TESTS OF VARIOUS ARSENICALS COMBINED WITH BORDEAUX MIXTURE ON THE 



FOLIAGE OF GRAPE. 



Several arsenicals in combination with Bordeaux mixture (4-4-50) 

 were tested on grape foliage at the vineyard of William Birkit, of Glen- 

 lord, Mich. Two applications were made with a power sprayer, 

 June 23 and July 2, 1914, 50 gallons to the plat. 



Plat I (applications 1 and 2), commercial arsenate of lead (powder), 

 1| to 50; Plat II (applications 1 and 2), arsenate of calcium, home- 

 made (sodium arsenate crystals, 18 ounces + calcium chlorid to 50); 

 Plat III (applications 1 and 2), arsenate of zinc, homemade (sodium 

 arsenate crystals, 18 ounces + zinc sulphate to 50); Plat IV (applica- 

 tion 1), commercial arsenate of calcium (paste), 3 to 50, (application 

 2) homemade arsenate of calcium (sodium arsenate crystals, 18 

 ounces + stone lime, 3 pounds to 50); PlatV (application 1), commer- 

 cial arsenite of zinc (paste), If to 50 (application 2), commercial 

 arsenite of zinc (powder), 18 ounces to 50. 



No foliage injury resulted from the applications of these arsenicals. 



SUMMARIZED REVIEW. 



ARSENATE OF LEAD. 



LABORATORY TESTS. 



Used alone. — Arsenate of lead was used throughout the experi- 

 mental work as a basis of comparison for the other compounds tested. 

 The rapidity of killing was greatest with diplumbio arsenate of lead, 

 while the triplumbic form was the slowest. Arsenate of lead of a 

 mixed diplumbic and triplumbic composition closely approached the 

 effectiveness of the diplumbio form. Commercial arsenate of lead No. 1 

 (triplumbic) was likewise slower in killing than the other commercial 

 compounds, which were largely diplumbic. In tests with the several 

 forms of arsenate of lead upon tender foliage, the triplumbic, the 

 most insoluble form, was found to be the safest. 



With Tcerosene emulsion. — Arsenate of lead may be combined with 

 kerosene emulsion for the purpose of combating mandibulate and 

 haustellate insects. Although there is a slight breaking down of 

 the materials, the value of neither material is depreciated when used 

 jointly as a spray. In order to secure the best results, it is advisable 

 not to mix these materials until needed. In a general way this is appli- 

 cable to the use of most insecticides in combination. 



