Apr. 26, 1924 
Fumigation of Bean Weevils 
355 
The writer's observations, together with the foregoing experiments, seem to 
indicate that in the commercial fumigation of beans there are four outstanding 
causes for the unsatisfactory results obtained. The first is the use of fumigation 
rooms which are far from being gas-tight, another is the use of a poor grade of 
carbon disulphide, and the third is carrying on the fumigation at too low tempera¬ 
tures. Where none of these can be given as a cause for unsatisfactory results, 
a fourth may enter. This is too short an exposure. Reference to the foregoing 
tables will indicate that a small amount of hydrocyanic-acid gas or of carbon 
disulphide will do the work as efficiently in from 48 to 90 hours as twice the 
amount of the same fumigant will in 24 hours. 
With reference to carbon disulphide as a fumigant, Hinds ( 1 ) says: 
“As a matter of fact, most, if not all, of the killing will have occurred during the 
first 6 hours of exposure, and the building may be ventilated after that time, as 
a minimum, has elapsed, though it is better to wait 12 hours or longer." 
Undoubtedly this is the case when large amounts of carbon disulphide and only 
small quantities of beans are used, but the writer is convinced that where large 
quantities of beans are to be fumigated, or where relatively small amounts of the 
fumigant are used, a period much longer than six hours is required to make a 
complete kill. The writer finds that if the gas is not strong at the end of a 24- 
hour exposure, the room is so open that all weevils will not be killed if a large 
quantity of beans has been fumigated. In such a room a large quantity of the 
fumigant should be used, and only comparatively small quantities of beans 
should be fumigated. 
Where hydrocyanic-acid gas is used, the room must be sufficiently tight to 
allow the gas to penetrate the beans before it diffuses out of the room. As this 
gas is not heavier than air, it requires a much longer time than does carbon 
disulphide to penetrate the beans thoroughly; therefore, a minimum of 48 hours 
should be allowed when using it. 
A very satisfactory bean fumigator can be constructed at a moderate price, the 
cost being determined by the size and location of the fumigator. It should have 
double walls, floor, and ceiling, made of tongue-and-groove, 1-inch lumber lined 
with tarred paper, having all joints sealed. All openings should be closed with 
specially constructed doors of the icehouse type or other type which can be 
sealed air-tight. 
A more expensive fumigator can be constructed of concrete or brick, having all 
joints properly sealed. 
CONCLUSIONS 
In commercial work there appears to be an unnecessary fear against the use of 
hydrocyanic-acid gas, because of its poisonous nature, but with the care that 
should be exercised in the use of carbon disulphide, hydrocyanic-acid gas can be 
used with safety. 
In commercial work, as well as in scientific work, opinions differ as to the effici¬ 
ency of carbon disulphide as a fumigant against bean weevils. While this appears 
to be due principally to three factors, in some instances a fourth factor may enter. 
These factors are: 
1. The use of a room or fumigatorium which is far from being gas-tight. 
2. The use of an inferior grade of carbon disulphide. 
3. Carrying on the work of fumigation at too low temperatures. 
4. (Which may enter when large quantities of beans are being fumigated and 
when unsatisfactory results can be charged to neither of the first three factors.) 
Too short an exposure. No. 1, above, frequently resolves itself into too short an 
exposure. 
94527—24t-5 
