INSECTICIDES. 83 



Sprayed May 24, 1897 : 

 May 26. No results. 

 May 28. So results. 

 May 29. No results. 



June 3. Few larvae dead ; foliage burned ; tender foliage badly 

 burned. Discontinued 



The barium arsenate used in the two preceding experi- 

 ments had stood in the " mother liquor" all winter, and had 

 developed a considerable amount of soluble arsenic. In the 

 following experiment the barium arsenate was freshly pre- 

 pared : 



Ten pounds to 150 gallons ; glucose, 1 gallon to 150 ; 100 

 square rods oak, pine and white birch brush ; larvas in fourth 

 and fifth stages. Hawkes' Farm, Saugus. 



Sprayed June 18-19, 1897 :- 



June 24. Many larvre dead. Special Inspector Little agrees with me in 

 estimating that GO per cent, of the larvas have been killed 

 Not as many dead as where arsenate of lead, 20-150, is 

 used. No burning apparent ; poison does not show well 

 on foliage 



June 29. Sprayed area in about the same condition as on June 24 ; 

 more larvae have died, but there are many large ones still 

 feeding ; bushes are being stripped ; poison disappeared ; 

 no burning of note. 



July 3. Poison has stopped killing ; slight biiruing on tender foli- 

 age ; effect not as good as where arsenate of lead, 20-150, 

 is used. The greatest fault seems to be in the ease with 

 which the poison is washed from the foliage Larvce 

 pupating. Discontinued. 



The experiments with barium arsenate in 1896 gave so 

 good results that we were hopeful that this insecticide would 

 prove superior to lead arsenate. Its killing effects on larvas 

 in confinement are certainly superior to those of arsenate of 

 lead. In the field spraying operations it was found that the 

 poison did not adhere to the foliage for a sufficiently long 

 time to kill the larvae. With the lessening of the cost of 

 arsenate of lead we have now effected, barium arsenate can- 

 not compete with it. 



