THE WEATHER AND THE WEEVIL 103 



eral Insecticide and Fungicide Bureau also sampled large 

 shipments and condemned the defective lots. Machines 

 were worked out by department designers and the models 

 were covered by patents dedicated to the public. Blue 

 prints of these patents were sent to all interested man- 

 ufacturers. 49 



After the difficulty with calcium arsenate and machines, 

 Coad announced two principles in the 1920 Yearbook. 

 First, "Raise a cloud of dust and let it settle." Second, 

 "The weevil can be controlled by means of calcium arse- 

 nate dust if the dust is applied at the right season at the 

 right interval and in the right way." The difficulties 

 exist in the fact that the control does not last long after 

 the poison is applied and that the weevils are reduced, 

 never exterminated. It proved useless to attempt to get 

 weevils early in the season. The greatest difficulty was 

 found in attempting to tell when to start and stop poison- 

 ing. 50 In 1922 Coad decided calcium arsenate was beyond 

 the experimental stage and turned the method loose to 

 go of its own momentum. 



As weevil prevention became a standardized technique 

 it was thought that the menace of the insect would be 

 removed from the risks of production and become a stand- 

 ard item in the cost of production. The Department real- 

 ized this when it advised against the use of the method 

 unless the yield per acre is at least a third of a bale 

 and the cost of application not more per acre than the 

 price of a hundred pounds of seed cotton. 51 



Coad and the great Scott Plantation, Mississippi, man- 

 aged by the Delta Pine and Land Company, dusted 



49 B. R. Coad, "Killing Boll Weevil with Poison Dust," Dept. 

 of Agriculture Yearbook, 1920. 50 Ibid., pp. 341-43. 

 51 The Boll Weevil Problem, p. 15. 





