INSECTICIDAL EFFECT OF COLD STORAGE ON BEAN 
WEEVILS 1 
By A. O. Larson and Perez Simmons 
Assistant Entomologists, Bureau of Entomology, United States Department of Agriculture 2 
INTRODUCTION 
The present paper is a report on the insecticidal efficiency of certain 
commercial cold-storage temperatures upon our two most destructive 
insect pests of stored legumes, Bruchus obtectus Say, the common bean 
weevil, and Bruchus quadrimaculatus Fab., the four-spotted bean weevil. 
The effectiveness of cold in protecting beans, peas, and cowpeas against 
weevil attack has long been recognized, but relatively little attention 
has been given by investigators to the use of low temperatures for killing 
weevils which are present in stored legumes. 
Duvel (2 ) 3 found that refrigeration at 32 0 to 34 0 F. was a perfect 
protection. Krall (4) concluded that eggs as well as all stages of the 
cowpea weevil, Bruchus chinensis L., can be killed by storage at 32 0 F. 
or colder (duration of exposure not given). Garman (3) stated that a 
temperature of 32 0 F. suspends the activity of the weevils and in time 
may kill them, although short exposures to this temperature apparently 
have no killing effect. He also concluded that all stages including eggs 
may be killed by one night’s exposure to zero weather. The foregoing 
writers found that the germinating power of the seeds is not injured by 
refrigeration, even (2) for 20 months. Back and Duckett ( 1 ), Severin (5), 
and others stated that little or no development takes place at or below 
50° F.; and Garman (j), speaking of temperatures of 35 0 to 40° F., 
wrote that “even these temperatures stop the work of the insects, 
though they will not entirely destroy them.” 
The present report summarizes experiments with Bruchus obtectus in 
California .pink beans ( Phaseolus vulgaris) and with B. quadrimaculatus 
in black-eye cowpeas or beans (Vigna sinensis). The results of work 
with the two species are here considered separately. 
COLD-STORAGE EXPERIMENTS WITH BRUCHUS OBTECTUS 
SCOPE AND METHOD 
These experiments included the refrigeration of 92,484 California 
pink beans infested with an estimated total of 114,200 larvae, pupae, 
and adults. The temperatures tested, 32 0 and 36° F., were obtained in a 
modern cold-storage plant at Stockton, Calif., where inspection of the 
rooms by employees every two hours served to keep the desired tem¬ 
peratures fairly constant. The term “constant temperature” is used 
here in the commercial sense, and it is assumed that there were occasional 
1 Accepted for publication Nov. 19, 1923. 
2 The writers wish to acknowledge their indebtedness to Dr. E. A. Back for valuable suggestions; to 
E- Nelson and A. H. Amis, laboratory assistants, for painstaking aid in the examination of seeds; and to 
ice and storage companies at Stockton and Pasadena, Calif.,, for hearty cooperation in making possible 
the experiments reported herein. 
8 Reference is made by number (italic) to “Literature cited,” p. 105. 
( 99 ) 
Journal of Agricultural Research, 
Washington, D. C. 
Vol. XXVII, No. 2 
Jan. 12, 1924 
Key No. K-125 
