UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 796 



Contribution from the Bureau of Entomology 

 L. O. HOWARD, Chief 



Washington, D. C. October 21, 1919 



USE OF TOXIC GASES AS A POSSIBLE MEANS OF 

 CONTROL OF THE PEACH-TREE BORER. 



By E. B. Blakeslee, Entomological Assisiant, Deciduous Fruit Insect Investi- 

 gations. 



CONTENTS. 



Page. Page. 



Introduction 1 I Experimental results 3 



Experimental procedure 2 I Summary 22 



INTRODUCTION. 



The study of poisonous gases and their use as a possible means of 

 control of the peach-tree borer, Sanninoidea exitiosa Say, of which 

 the present paper is a brief report, was begun in 1915, under the direc- 

 tion of Dr. A. L. Quaintance, in charge of deciduous fruit insect 

 investigations, of the Bureau of Entomolog3^ In this investigation 

 the attempt has been made to develop a method of control by the 

 use of local applications of volatile toxic compounds in the soil at 

 the base of the trees. On account of the intimate association of the 

 insect and its host, any gas fully efficient as a larvicide must neces- 

 sarily have more or less effect upon the tree. In this respect, how- 

 ever, the problem presents nothing unusual, as the application of 

 insecticides generally and the fumigation of living plants especially 

 is restricted to a greater or less extent by the same limitation. In 

 the case of the peach-tree borer the insect and its host are by no 

 means susceptible to fumigation in the same degree. Also, for vari- 

 ous reasons, a much wider margin of safety to the tree is afforded 

 by some gases than by others. 



It has been necessary, in regard to fumigation, to take into con- 

 sideration the manner in which it is affected by soil and atmospheric 

 temperatures, soil type, soil moisture, rainfall, seasonal development 

 of the insect and its host, and their relation to the chemical prop- 

 erties of the materials tested, such as the volatility and solubility 

 of the gas, etc. In 1916 daily determinations of soil moisture and 

 records of soil and atmospheric temperatures and rainfall were ob- 

 tained in connection with each experiment, but on account of the 



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