64 MANUAL OF VEGETABLE-GARDEN INSECTS 



The Control of Pea and Bean Weevils 



Seed infested by living weevils should never be used for 

 planting, for it is in this way that many of the weevils gain 

 access to the field. Neither is it good economy to use infested 

 seed for planting in which the weevils have been killed, because 

 the percentage of germination of such seed is low and the 

 plants produced are weak and unproductive. In the case of 

 the pea weevil and the broad bean weevil, species that do not 

 breed in dried seed, the insects may be killed by holding over 

 the seed until the second year before planting. The weevils 

 will emerge in storage and, being unable to escape, will die 

 without laying eggs. In the case of the bean weevil, the four- 

 spotted weevil and the cowpea weevil, in which breeding con- 

 tinues in the dried seeds, holding over the seed would be use- 

 less. Fumigation with carbon bisulfid is the most efficient and 

 practicable method of killing the weevils in stored seed. To be 

 most eft'ective, the treatment should be made in the fall soon 

 after harvesting. The seed is placed in a tight barrel or box 

 to which a cover has been fitted as nearly air-tight as possible. 

 Carbon bisulfid is used at the rate of ^ to 1 ounce to a bushel. 

 In larger quantities in specially constructed fumigating cham- 

 bers, the weevils can be killed by using carbon bisulfid at the 

 rate of 3 pounds to 100 cubic feet. The liquid should be placed 

 in some shallow dish like a pie tin on top of the seed. The 

 fumigating box should then be covered tightly and fumigation 

 should be allowed to continue for twenty-four to thirty-six hours. 

 More satisfactory results wdll be obtained if the temperature 

 is kept at 70 degrees F. or above. In fumigating, care should 

 be taken not to smoke t>r to bring fire of any kind in contact 

 with the gas, as the carbon bisulfid vapor is very inflammable. 



When there is only a small quantity of seed to be treated 

 and when it is impracticable to fumigate, the weevils may be 

 killed by suspending the seed in a bag in a kettle of cold water 



