16 
BCLLETIX 807, U. S. DEPARTMENT OF AGRICULTURE. 
destroyed. The experiments were carried on mostly in the fall, 
shortly after all the adults had formed. Other experiments during 
the spring, toward the end of the life of most of the weevils, gave a 
complete killing with a lower degree of heat and a shorter time. 
Treatment of from 125° to 145° F. for several hours, as recommended 
for bean and pea weevils in a recent Farmers* Bulletin (7). was not 
tried. Experiments indicated, however, that the horse-bean weevil 
is more difficult to kill than the ordinary bean weevil. Unless the 
heat can be easily controlled and not allowed to go much above l-i5 c , 
other remedies will be much safer to use. 
FUMIGATION. 
Sulphur was first tried, using varying strengths up to 2 pounds 
to 100 cubic feet of space for a period of 3 hours, and proved un- 
successful. 
The standard remedy for bean weevils, carbon disulphid, was 
next tried. The experiments were arranged to compare the effect 
of infested beans fumigated while the insects were in the imm ature 
stages and after all had reached the adult stage. Examination of 
beans during the experiment gave the following results : 
Table XII. — Development of Bruchus rufimanus Aug. 15 and 17. 1918. at Al- 
hambra, Calif. 
Per cent. 
One-half to three-fourths grown larvae 37. 6 
Full grown larva? . 20. 9 
Total larva? 58. 5 
Pupa? _ 
Adults 
20. 
21.5 
.Table XIII. — Effect of carbon disulphid on the broad-bean weevil. 
Percentage of beans with all weevils dead . 
Pounds CS 2 per 1.000 cubic feet. 
Exposed 18 hours. 
Exposed 24 hours. 
Treated 
in 
August. 
Treated 
in 
October. 
Treated 
in 
August. 
Treated 
in 
October. 
Check, not treated 
43 
55 
55 
69 
70 
CO 
74 
14 
43 
52 
52 
60 
82 
62 
79 
14 
2 
3 
4 
S3 
94 
90 
100 
99 
100 
SI 
5 .. 
96 
6 
99 
100 
8 
100 
9. 10, 12, 15, 20 , 
100 
Conclusions from the carbon disulphid fumigation experiments : 
1. Exposure in October when the insects were in the adult stage 
gave a 20 per cent better result than in August, when they were in 
the larval stage. 
