196 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



sary to study the effect for several years before it will be possible to 

 give positive results. 



Each spraying solution was applied in three strengths, double the 

 normal, ten times and twenty times the normal strength. The double 

 strength arsenate of lead produced no effect on the limb. The limbs 

 upon which the two higher strengths of this solution were applied, 

 showed a very slight burning on a few of the leaves soon afterwards, 

 but the injury did not increase through the season. 



The Kedzie arsenate showed no injury in any of the three strengths 

 used. 



Paris green in double strength showed no injury at all. The ten 

 and twenty times normal strength caused a slight burning along the 

 edges of the leaves. 



A soluble arsenate (sodium arsenate) was also applied in three 

 strengths, one-twentieth, the same amount, and twice as much as there 

 would be of insoluble arsenic applied in the form of lead arsenate in 

 a year of normal spraying. The two weaker strengths showed no 

 injury at all. The double strength produced a browning of a few 

 leaves early in the experiment but this did not increase and never 

 became at all serious. 



The above summary of the first year's work is, of course, in no 

 sense conclusive but it would seem to indicate that the bark of an 

 apple tree is not seriously affected by the normal spraying solutions 

 even where they remain in contact with it for considerable times. 

 The fact that the weaker strengths of the soluble arsenate produced 

 no apparent injury is also quite suggestive because if the spraying 

 solutions should fall into an alkaline soil at the base of the tree it 

 is not likely that there would be more arsenic set free in a single 

 season than was applied directly to the tree in this case, and there- 

 fore, if injury should be produced under the latter condition, some 

 other factor would be necessary to account for the condition, other 

 than the arsenic alone. And as alkali has killed thousands of trees 

 where no arsenical sprays have ever been applied, it would seem 

 natural to infer that the death of the trees, even where both sub- 

 stances were present, might be due, in a large measure at least, to 

 the alkaline factor. 



A number of other experiments have been carried on, such as 

 growing various crops in soil taken from around the base of trees 

 said to have died from arsenical poisoning; growing crops in soils 

 in which large amounts of the different spraying solutions have been 

 mixed, etc. Up to the present time, all of the results tend to confirm 

 the conclusions drawn in the cases cited above. 



