INSECTICIDES. 89 



Twenty pounds to 150 gallons; glucose, 1 gallon to 150; 

 red oak and white oak trees of medium size, badly infested by 

 larvae in fifth and sixth stages. Pine Hill Path, Metropolitan 

 Park Reservation, Medford. 



Sprayed June 26, 1897 : - 



June 29. Killing well. Dead larvre plenty in path. 



July 1. Killing well. Dead larvre plenty in path. 



July 5. Killing well. 



July 10. Killing well. Sixty per cent, of the larva) dead. 



July 21. Poison still killing, although the greater part of the larva; 

 have transformed. No burning of foliage. The results 

 from the experiment are equally as good as those where 

 the tri -plumbic arsenate is used. 



TRI-PLUMBIC ARSENATE. 



Field Experiment. 



Check experiment on the preceding ; 20 pounds to 150 

 gallons ; opposite side of path. 



Sprayed June 26, 1897 : - 

 June 29. Killing well. 



July 1. Killing well Plenty of dead larvse. 

 July o. Killing well. Plenty of dead larvse. 

 July 10. Still killing ; no burning ; about sixty per cent, of the larvse 



dead. 

 July 21. Few dead larvte ; greater part pupated. 



The di-plumbic arsenate was prepared from nitrate of lead. 

 So far, this insecticide seems equal if not superior to the 

 tri-plumbic arsenate. Extensive field experiments will be 

 made with the di-plumbic arsenate- during the season of 

 1898, should the Legislature provide means for the continua- 

 tion of this work. 



The "di-plumbic arsenate" is composed of about two-thirds 

 di-plunibic arsenate and one-third tri-plumbic arsenate. The 

 tri-plumbic arsenate is approximately pure. 



