170 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 9 



in the work. Holes varying from one to three inches deep were bored 

 in the trunks with one-half-inch and three-eighths-inch augurs, at dis- 

 tances varjdng from a few inches to four feet above the ground. 

 Charges of 98 per cent pure potassium cyanide, each weighing from 

 one to ten grams, were placed in the holes and corks tightly driven 

 into the holes. As checks, several trees were treated in exactly the 

 same way, excepting that no cyanide was used in them. This work 

 was done during the last of March and first of April. On May 10, 

 the corks were removed and it was found that the cyanide had com- 

 pletely dissolved in the sap, no residue being present in the holes. 

 A slight odor of cyanide seemed to be present, and the wood sur- 

 rounding the interior of the holes was moist and dark brown in color. 

 Most of the corks were replaced in the holes. On June 3, it was noted 

 that the trees treated with cyanide seemed to have a darker, healthier 

 foliage than their neighbors. The corks were again removed and the 

 bark cut away from the holes in several trees. It was found that both 

 the cambium and sapwood were dark and dry, both above and below 

 the hole for several inches. This injury did not extend laterally from 

 it and was just as deep as the hole. Beyond the inner end of the hole 

 the injury had not extended inward. 



On November 22, all of the trees were again examined, and the 

 bark cut away farther from the holes. The results were quite uniform. 

 The wood was blackened above and below the holes where cyanide 

 had been inserted. No injury was found where no cyanide was used 

 in the holes. A number of borers were taken alive from elm and plum 

 trees within a few inches of the holes where cyanide had been placed. 

 The blackened areas on trees which had been examined June 3 had 

 increased to several times their length on that date. This black 

 wood always occurred as a streak the width of the hole and followed 

 the direction of the grain of the wood above and below the hole. In 

 several cases the cambium and inner bark had dried and had been 

 pushed out from the black streak and a callous growth was starting 

 from both sides beneath the bark over the entire length of the streak. 



This shows that the tree is injured only above and below the opening 

 in which the cyanide is placed and that the healthy wood on both 

 sides is attempting to heal the wound caused by the cyanide. No 

 dead insects were found but in some of/ the holes left uncorked since 

 June sow bugs were found to be breeding. 



Dr. J. H. Merrill of the Kansas Agricultural College has been carry- 

 ing on some experiments along this Hne. Professor Dean advises me 

 that the results obtained were similar to those just given. The effects 

 on the trees treated, as noted by both departments, was that the foliage 

 became a distinctly darker and richer green after the introduction of 

 the cyanide. 



