April, '10] BALL AND OTHERS: ARSENICAL POISONING 195 



Experimental Results 



It has been claimed that the greatest injury to the trees from the 

 application of arsenicals was through their corrosive action in de- 

 stroying the bark at the base of the trees. In order to test this ex- 

 perimentally as well as the possibility of the tree absorbing sufficient 

 free arsenic through its roots to cause systemic poisoning, varying 

 strengths of spraying compounds were applied to different Ben Davis 

 trees. One set of trees received as much lead arsenate as would be re- 

 quired to protect them for ten years ; another set for twenty years, and 

 still another set with the amount required to protect trees for forty 

 years. This would be approximately the amount applied to a tree 

 during its entire life, as there are several years in which no sprays are 

 applied at the beginning, and an occasional year in which there is no 

 fruit and therefore.no application of spraying material. All of the 

 trees matured their fruit in perfect shape and even in the case of the 

 heaviest application, the leaves were not seriously burned. The 

 material was applied in the form of a spray with sufficient water so 

 that it ran down the limbs and trunk in streams and dripped off from 

 every part of the tree on to the ground to such an extent that, while 

 the tree was whitened, and remained so all summer, the ground under 

 the entire head of the tree was so saturated with the arsenic as to 

 appear mouldy white to a depth of three or four inches. All of this 

 poison was applied at the regular spraying time in the spring and the 

 trees were irrigated in the normal manner during the season. An 

 examination made in the fall disclosed no apparent injury to the bark 

 of the trees at the crown and the roots near the surface had a normal 

 healthy appearance. Part of these applications were made where 

 there were weeds, alfalfa, and strawberries beneath the trees, and even 

 with the heaviest applications no injury was observed upon the 

 vegetation. 



It will be necessary, of course, to continue this experiment for a 

 number of years before any definite conclusions can be drawn, but 

 it would seem that if the arsenic in the soil is freed in sufficient quan- 

 tities from a few years' spraying to seriously injure or kill a tree, 

 that enough arsenic would be freed in one year under like conditions 

 from the excessive amount applied in this case to show some injury. 



In order to further test the corrosive action of the arsenical com- 

 pounds, the various spraying mixtures were applied directly to the 

 bark of medium sized limbs of bearing trees, and maintained in con- 

 tact with these limbs for a period of forty-five days during the latter 

 part of the growing season. These experiments will be repeated on a 

 much larger scale the coming season and it will, of course, be neces- 



