June, 1917.] ARSENICAL RESIDUES AFTER SPRAYING. 37 



In the face of the above record the writers feel that the subject 

 is one requiring much care in drawing conclusions. Considering 

 all of the data already cited in this bulletin, including the feeding 

 experiments, it is believed that the use of apples from trees 

 sprayed with arsenate of lead at the rate of 3 lbs. of the paste to 

 50 gallons of water offers very slight danger, even if the fruit 

 from such trees is consumed frequently, provided rains have 

 intervened after spraying. An occasional fruit might show as 

 much as .5 milligram or even 1 milligram AS2O3, but this 

 would not be common. Most of the fruit in the ordinary process 

 of handling, and subject to average weather conditions, would be 

 likely to exhibit only a small fraction of the above amounts per 

 fruit. If one is dealing with winter fruit which has been sprayed 

 two months or more prior to harvest, the residues would appear 

 negligible. In the case of early fruit, sprayed just before har- 

 vesting, the fruit should be wiped. 



EXPERIMENTS WITH LIVE STOCK. 

 DRIP FROM TREES. 



The amount of spray material that may be expected to lodge 

 on the ground beneath a sprayed tree naturally varies with several 

 factors. It will be less if the operator is careful and greater if he 

 is careless. It will likely increase as the total amount of material 

 applied to a tree is increased. It may be more when a coarse 

 nozzle is used than when a mist nozzle is employed. 



These factors concern the amount of liquid material. Another 

 and an important factor which will greatly influence the amount 

 of arsenic recoverable beneath the tree is the concentration of 

 spray material employed. If 10 gallons of spray material is 

 applied to a tree and if 2 gallons of this finds its way to the 

 ground, that which falls on the ground will carry increasing 

 amounts of arsenic as the concentration of the spray material is 

 increased. We should expect and shall find double the amount 

 of arsenic on the ground if the concentration of the spray material 

 is the equivalent of 6 lbs. of arsenate of lead paste to 50 gallons 

 of water than we shall find if the concentration is only 3 lbs. 

 Neither of these concentrations, nor any other in common use, 

 alters the physical character of the spray material in sufficient 

 degree to cause it to drip less readily. 



