CIRCULAR No. 523 MAY 1939 
UNITED STATES DEPARTMENT OF AGRICULTURE 
WASHINGTON, D. C. 
TOXICITY OF CERTAIN ORGANIC INSECTICIDES TO 
CODLING MOTH LARVAE IN LABORATORY TESTS 
By Dp eb SIEGLER, senior entomologist, and F. MuncEr, junior entomologist, 
Division of Fruit Insect Investigations, and L. E. Smiru, chemist, Division of 
Insecticide Investigations, Bureau of Entomology and Plant Quarantine 
CONTENTS 
Page Page 
Introductions se see ee ee Ae SResniEs OL Tests sae 5 eee oe ee 2 
IMICCR OG Seat ete re ae eee meee ASD ISCUSSION Soe eee eee See BEE ee es ee 8 
INTRODUCTION 
In view of the importance of insecticides to the fruit industry, 
laboratory investigations of the toxicity of compounds to the codling 
moth (Carpocapsa pomonella (L.)) have been continued. And it bas 
seemed fitting to keep primarily within the field of organic com- 
pounds because of the relatively small percentage of these compounds 
that have been studied in this connection. 
METHODS 
The toxicological results given in this circular were obtained for the 
most part from 1934 to 1936, inclusive, at the Agricultural Research 
Center, Beltsville, Md. All tests were made by means of the apple- 
plug method.! In explanation of the tables, it should be stated that 
the number of spray applications refers to the number of times the 
apple plugs on an endless belt passed beneath the spray nozzle. 
en two applications of spray material were made, the first spray 
deposit was allowed to dry before the second was applied. Except 
where otherwise noted in the tables, each compound was used at the 
rate of 4 pounds to 100 gallons of the carrier. | 
In the investigations of these organic compounds it was found that 
many of them were difficult to wet and therefore not easy to suspend 
uniformly in the carrier. In an attempt to improve this condition, 
wetting agents such as bentonite, alcohol, and other compounds were 
used in many of the experiments as an addition to the carrier. Al- 
though lead arsenate itself is readily suspended in water, wetting 
agents were added to it in some of the tests for purposes of comparison 
with the organic compounds similarly wetted. 
1 SIEGLER, E. H., and MUNGER, FRANCIS. A FIELD AND LABORATORY TECHNIQUE FOR TOXICOLOGICAL 
STUDIES OF THE CODLING MOTH. Jour. Econ. Ent. 26: 438-445, illus. 1933. 
MUNGER, F., and GAHAN, J. B. IMPROVEMENT IN “APPLE PLUG” TECHNIC FOR TOXICOLOGICAL 
STUDIES OF THE CODLING MOTH. Jour. Econ. Ent. 27: 1140-1142, illus. 1934, 
a 
117510—39 
