pound. Without the first specification, the poison will not be sufficiently insecti- 

 cidal; without the second, it may scorch the plants; without the third, it will not 

 produce a suitable dust cloud. 



The danger of the poison to man and animals is slight if proper precautions 

 are taken, but the risk of inhaling the poison or of absorption through the skin, 

 as well as thaPbf swallowing it, must be borne in mind. The poison is best ap- 

 plied at night when the humidity is high and the air calm. Rain washes it off much 

 more readily if it has been applied in very dry weather. 



Dusting machinery is of three kinds: hand guns, cart dusters, and power 

 dusters. Hand guns are suitable for only very small areas, or to supplement the 

 cart duster. The latter is hardly justified for less than 75 acres. Power dusters 

 are not very satisfactory. 



The expense of poisoning varies in different circumstances. Generally it is 

 hardly justified' unless the land is fertile enough for the plants to take full advan- 

 tage of the treatment, and unless the land would produce at least 1/2 a bale of 

 cotton an acre if there were no weevils. 



Calcium arsenate can also be used in the control of cotton leafworm, fall 

 army worm, etc. But if the weevil equipment is used solely for leafworm control, 

 the expense may be considerably reduced by mixing lime in equal parts with the 

 calcium arsenate and applying the mixture at the rate of 4 or 5 lbs. an acre. 



1920 - Ferris, E. B. Cotton growing in south Mississippi. Miss. Agr. Expt. Sta. B. 196, 

 8 p. Dec. 



Until the season of 1920, the Mississippi Station had made no attempt to con- 

 trol the cotton boll weevil with poisons. In that year the damage was so great that 

 some growers ploughed up their cotton and planted the lands in other crops. On 

 the station farm, in spite of several hand-pickings, many of the cotton stalks had 

 every square punctured. Hand dusting was then begun with calcium arsenate, 3 

 applications being given at intervals of about 6 days. After this treatment, the 

 percentage of infestation was so low that poisoning was stopped for a time and 

 begun again late in July. It is uncertain whether the good results were due to 

 poisoning or to the frequent rains that began about the same time. 



1920 - Howard, L. O. Report (1919-1920) of the entomologist. U. S. D. A. Bur. Ent. 

 Rpt. 36 p. Sept. 7. Wash. 



"With regard to southern crop pests, the use of calcium arsenate against the 

 cotton boll weevil . . . has been greatly extended. Suitable dusting machinery by 

 wheel-traction power has been devised, motor power dusters proving unsuit- 

 able." 



1920 - Newell, Wilmon, and Eli K. Bynum. Notes on poisoning the boll weevil. J. Econ. 

 Ent. 13(1):123-136. 



1. The mortality among boll weevils on cotton plants treated with lead and 

 calcium arsenates, and kept protected from all rain and dew, was appreciably 

 higher than the mortality on plants similarly treated but exposed to dew and 

 normal precipitation. Because the presence of dew or rain water on the cotton 

 plants did not increase the effectiveness of either lead or calcium arsenate as a 

 boll weevil poison, it was evident that mortality from the use of either of these 

 poisons was brought about by ingestion of the poison with the weevil's food and 

 not by drinking the so-called "poisoned dew." 



2. Dew collected from cotton plants treated with lead arsenate at the rate 



of approximately 8 lbs. per acre contained 6.7 p. p.m. of arsenic. Dew from plants 

 treated with calcium arsenate at the same rate contained from 10.0 to 43.5 p. p.m. 

 of arsenic. The dew was collected only from cotton leaves that showed a distinct, 

 thorough white coating of the arsenates. 



3. Boll weevils, deprived of all food and having dew from treated plants as 

 the only source of moisture, suffered a greater mortality than boll weevils con- 

 fined on clear water. This showed that the dew contained sufficient arsenic to 

 produce death when the weevils were compelled to take the dew, and no other food 



