22 BULLETIN 796, V. S. DEPARTMENT OF AGPJCULTUEE. 



The writer is indebted to a number of observers for cooperation 

 in experiments made in various parts of the country during the 

 season of 1918. In Ohio the treatments and examinations at San- 

 dusky and Vermilion were made by Mr. G. A, Runner, in charge of 

 the laboratory of the Bureau of Entomology at Sandusky, in coopera- 

 tion with Mr. H. J. Speaker, of the bureau of horticulture, Ohio De- 

 partment of Agriculture. The work in southern Ohio at Wakefield 

 was conducted by Mr. Speaker. At Springdale, Ark., the observa- 

 tions were made hj Mr. A. J. Ackerman, of the Bureau of Entomol- 

 ogy, and Mr. F. L. Pierce, of the Bureau of Plant Industry. At Fort 

 Valley, Ga., the work was carried out by Mr. J. J. Culver, of the 

 Bureau of Entomology, and the writer. The writer is also especially 

 indebted to Mr. B. R. Leach, in charge of the bureau laboratory at 

 Winchester, Va., for many valuable suggestions and for cooperation 

 and assistance in the experiments in Virginia, West Virginia, and 

 Maryland. 



SUMMARY. 



(1) It has been found impossible to standardize the use of carbon 

 disulphid and carbon tetrachlorid as treatments for the peach borer. 

 The great volatility of these substances at ordinary temperatures 

 renders them too sensitive to varying conditions of soil porosity. 



(2) Sodium cyanid on account of its solubility was too susceptible 

 to the effects of variation in soil moisture and soil type, and proved 

 to be injurious to trees. 



(3) Naphthalene on account of its low volatility within the sea- 

 sonal range of soil temperatures was only a partially effective larvi- 

 cide for a very short period in midsummer. 



(4) P-dichlorobenzene has proved quite effective over a Avide 

 range of varying conditions imposed by field practice, with a consid- 

 erable margin of safety for trees six years and over. 



In making the application the surface crust about the collar of 

 the tree is broken. Excessive amounts of gummy exudations at the 

 surface are removed. The lower levels of soil are disturbed as little 

 as possible, and the required dose is distributed evenly about the 

 trunk in a band 1 to 2 inches in width. (See Plate I, A.) Two or 

 three shovels of earth are then placed over the material, and com- 

 pacted with the back of the shovel, being mounded slightly to cover 

 surface galleries (Plate I, B). 



In the latitude of Washington and northern Virginia about Sep- 

 tember 10 has been found to be the most satisfactory time of appli- 

 cation. Based on the insect's seasonal history, the theoretical time 

 of application in the North generally would be about September 1; 

 in the Ozarks, September 25 ; and in Georgia and the "cotton belt, 

 October 10. 



