32 .KUKXAL OF ECONOMIC FJXTOMOLOGY [Vol. 3 



of cherry slugs, and the larva3 of the white ermine moth, Diacrisia 

 virginica Fab., but I did not compare the results in these cases with 

 the effects of other arsenical poisons in parallel tests. 



Mr. J. B. Smith: Will Professor Gillette please tell us how this 

 poison is prepared and where it can be secured? 



Mr. Gillette: The poison was prepared for me by Doctor Head- 

 den and the method of making it is explained in the footnote given 

 in the paper. I do not think it can be secured at present, unless it is 

 made up specially for the purpose. 



Mr. Forbes : I realize that it is getting late, yet I think if the sub- 

 ject of arsenical poisoning on fruit trees is not taken up we will lose 

 a great deal of information which should be of great value to the 

 members of this Association. 



Doctor Headden has been working on this matter in Colorado, and 

 while some of his results may refer directly to Colorado conditions, I 

 think the whole matter should be of great interest to our members, 

 especially as some of us have conditions to deal with which are in a 

 way similar to those in his state. I trust we shall have time to hear 

 from Doctor Headden concerning this matter. 



President Britton : We will be glad to hear from Doctor Head- 

 den. 



ARSENICAL POISONING OF FRUIT TREES 



By W. P. Headden, Fort Collins, Col. 

 [Summary of remarks] 



There are some facts in regard to which all agree, namely, that we 

 have many sick fruit trees; particularly apple and pear trees. I 

 do not for a moment wish to assert that all of these sick trees are suf- 

 fering from arsenical poisoning, nor that all of the dead ones have 

 been killed by arsenic. But I do believe that many of them have died 

 from this cause. Other causes which might have produced death are 

 winter killing, accumulation of nitrates in the soil, fungi of different 

 kinds, possibly blight and still other causes. 



The trees referred to have not been killed by freezing. We have 

 very little of this in the state, and these cases present no similarity 

 to those attributed to arsenical poisoning. The fornfer in this latitude 

 produces its injury above the surface of the ground, and the injury 

 is really effected beneath the bark. Arsenic begins its attack below 

 the surface of the ground and on the outside of the bark, converting 



