Experiments in Tablet Insertion 



The technique of inserting tablets into trees was developed during the 

 peeling operations which have just been described. The spud used in this 

 operation is about one-half inch in width and a little less than a quarter 

 of an inch thick. The end is flattened and slightly bent so as to conform to 

 the curve of the tree. It is easily slipped between the wood and bark for 

 several inches before tearing occurs. If the tool is thus forced horizontally 

 between the wood and bark for two or three inches and then withdrawn, a 

 very good pocket is formed. Such a pocket is an ideal repository for testing 

 the action of various chemicals. It was found that tablets could be made of 

 ammate, and that the weight of the chemical used in each tablet was easily 

 controlled. Thirty ammate tablets were prepared which ranged in weight from 

 one-ihalf to three grams. They were first tried as a means of thinning a 22- 

 year-old plantation. The trees to be eliminated were selected and numbered. 

 Bark pockets were made with the small spud and one tablet was inserted in 

 each pocket. After a week, browning could be observed in the tops and 

 branches of all treated trees. 



A second plot was established and treated as soon as browning was ob- 

 served in Plot No. 1. This consisted of 50 trees, each of which was treated 

 with a two-gram ammate tablet. The reaction was identical to that previously 

 observed. 



In a white-pine plantation of this kind there is considerable variation in 

 the size and vigor of the individual trees. There had been uniformly repeated 

 attacks by the white pine weevil so that some trees had multiple stems with 

 heavy branches beginning at a height of five or six feet. In such trees it 

 was not uncommon to find that the effect of the ammate could be seen 

 principally in one branch while the others remained healthy. Later the exact 

 path of the chemical reaction was easily observed as the bark became darker 

 in a strip running upward from the point where the tablet was inserted. 

 This strip varied little in width in its upward course, but if anything became 

 somewhat wider. In other words it enclosed a little more of the perimeter 

 of the tree as it progressed upward. The edges of the strip were so well de- 

 fined that they could be seen as two parallel lines following the grain. In 

 some cases, the strip was spiral in form so that if an insertion was made on 

 one side of a tree the effect could be seen spiralling upward to the opposite 

 side in a matter of 16 feet or less. Below the tablet insertion the strip came 

 to a point in 10 to 12 inches. 



The entire operation of making bark pockets and inserting tablets in 

 50 trees of Plot No. 2 took 25 minutes. 



Paper Strips Treated with Sodium Arsenite 



One objection to using ammate tablets is that they absorb moisture so 

 easily they tend to fuse in storage. To overcome this difficulty, two-inch 

 blotting paper squares were cut and soaked in an ammate solution. It was 

 found that after drying they could be handled quite easily, and that the 

 effect on trees was the same as when tablets were used. In either case the 

 dry chemical was readily absorbed. 



Because of prejudice, sodium arsenite had not been used previously in 

 these tests. However, treated tabs of blotting paper tucked safely under the 

 bark with none of the material left on the outside of the tree appeared to 



