MISCELLANEOUS INSECTICIDE INVESTIGATIONS. 



21 



Experiment XII. 



COMBINED SPRAYS AGAINST LARVAE OP THE FALL WEBWORM. 



The purpose of Experiment XII was to test by the laboratory 

 method certain spray combinations, some of which were being used 

 under field conditions. The arsenate of calcium used in this experi- 

 ment was prepared by using 4 pounds of stone lime, to which was 

 added 18 ounces of sodium-arsenate crystals during the slaking. 

 This, when mixed with the proper quantity of water, was used for 

 the making of Bordeaux mixture 4-4-50. This combination was 

 made with a view to using it as a vineyard spray. The results of 

 this experiment appear in Table XII. 



Table XII. — Tests of the hilling effect of various materials on the fall webworm. 

 [Experiment started July 24, 1914, Benton Harbor, Mich.; 10 larvae in each lot.] 



Name and dilution. 



Dates of exami- 

 nation and num- 

 ber of larvae 

 dying in each lot. 



na 



M 



CJ 



S 

 3 



a 



"3 



o 



£3 







July. 



August. 



CD 







29 



1 



7 



13 



7 

 5 

 7 

 2 

 7 

 4 



3 

 1 

 3 

 4 

 3 

 







10 

 10 

 10 

 10 

 10 

 10 



8 

 14 



8 

 20 



8 

 20 



4 





3 



1 



5 



1 



3 



6 



1 





10 



14 



8 



5 

 1 



2 



5 

 1 







10 



10 

 2 



8 

 8 















w a) 

 ■fl 8 



Arsenate of lead powder, 11-50+ lime-sulphur, 1J-50 



Lime-sulphur, 1^—50 



Arsenate of lead powder, 1J-50 



Commercial sodium sulphid, 2-50 



Commercialsodium sulphid, 2-50+arsenateof lead powder,l£-50 



Commercial barium tetrasulphid, 5-50 



Commercial barium tetrasulphid, 5-50+ arsenate of lead pow- 

 der, 1J-50 



Sodium arsenate (crystals, tech. pure), 18 ounces+ Bordeaux 

 mixture, 4-4-50 



Sodium arsenate (crystals, tech. pure), 18 ounces+ Bordeaux 

 mixture, 4-4-50+nicotine sulphate, 40 per cent, 1-1,600 



Check (unsprayed) 



0.18 

 0.82 

 0.46 

 3.34 

 0.22 

 5.76 



0.34 



0.10 

 13.50 



As will be noted in Table XII, arsenate of lead, either alone or com- 

 bined with lime-sulphur solution or commercial sodium sulphid, 

 killed all the larvae in 8 days. The same arsenical combined with 

 commercial barium tetrasulphid compound required 14 days to kill 

 the 10 larvae, although 9 of these were recorded dead at the end of 

 the eighth day. The arsenate of calcium made in the same operation 

 of slaking the stone lime for Bordeaux mixture caused the death of 

 all the larvae in 9 days. This combination was tested in a vineyard 

 and caused no foliage injury. At the end of 20 days, when the experi- 

 ment was closed, but two larvae of the unsprayed lot were dead. 



