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 Assistant, Deciduous Fruit Insect Investi- 
CONTENTS. 
Page. Page. 
Introduction 1 j 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, Samiinoidea exitwsa 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 Entomology. 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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