cause of this showed that the initial infestations were due to phototropic reaction 

 of the winged female to a white dust, infestation being induced not only with cal- 

 cium arsenate but also with calcium carbonate, starch, or flour. Plants dusted 

 with calcium arsenate, colored green, remained uninfested. The fact that infesta- 

 tion becomes more intense on small areas of dusted cotton than in large ones is 

 accounted for by the lack of opportunity for selection afforded to the aphids in the 

 latter case. 



1927 - Walker, H. W., and J. E. Mills. Chemical warfare service boll weevil, Anthono - 



mus grandis , investigations (P. R.). Indus. & Eng. Chem. 1 9(6):703-7 1 1. 



Preliminary tests have been made on more than 1,000 poisons or poisonous 

 mixtures against the boll weevil, and about 50 of these have shown a toxicity equal 

 to or greater than calcium arsenate. About 20 of these materials show little or no 

 injury to the cotton plant. A total of 100,000 weevils were used in the tests made. 



Barium, lead, zinc, mercury, and, to a lesser extent, iron, have shown some 

 measure of toxicity to the boll weevil when combined with other chemical groups 

 in themselves harmless, and the toxicity of these metals seems, in general, to be 

 retained when combined with arsenic, and to increase the toxicity of the resulting 

 arsenical. Sodium fluosilicate, barium floride and cryolite seem to be as effec- 

 tive as calcium arsenate, measured by volume. These substances should be sub- 

 jected to further careful and extensive field tests to determine their exact value, 

 using 10% to 15 lbs. to an acre. Every effort should be made to lessen the density 

 of these poisons so that the amount per acre used can be decreased. 



It is believed that an advantage will be gained if the percentage of arsenic in 

 calcium arsenate is reduced and a larger amount used per acre. Arsenic trioxide 

 or arsenic pentoxide, in relatively small percentages, absorbed on coal dust or 

 some similar vehicle, may make an effective economical poison against the boll 

 weevil if some agent such as oil be used to prevent scorching. Only occasional 

 scorching is produced by 1-1/2% arsenic trioxide on coal dust at the rate of 10 to 

 15 lbs. an acre. The weevil seems to get most of the poison by more or less ac- 

 cidentally coming into contact with the dust particles and subsequently taking 

 them into its system, but it does obtain some poison through its food and drink. 



High concentrations of toxic gases are ineffective against the weevil, owing 

 to its apparent ability to suspend breathing. There may still be a possibility that 

 low concentrations of a persistent cumulative gas on absorbents may give effec- 

 tive control. The amount of arsenic in the best available form (soluble As^C^) 

 necessary to poison a weevil is estimated as 0.0025 cc (2.5 mg.) and the air 

 breathed by a weevil in an hour is roughly estimated as 0.46 cc. 



The work emphasizes the need for careful management of dusting machinery 

 so as to obtain an even distribution of the poison over the plant. A calm or a very 

 slight wind is a necessity. The cotton plant should be moist if calcium arsenate is 

 used. For the time being it is recommended that the method of control as de- 

 scribed by the Southern Agricultural Workers Association, using calcium arsenate 

 as a dust, or in special cases of a syrup mixture, be strictly adhered to. 



1928 - Anonymous. Entomology. Tex. Agr. Expt. Sta., 1927 Rpt. 40:36-41. Col. Sta. 



Findings that 70% of the cotton boll weevil are killed as a result of collect- 

 ing the particles of calcium arsenate dust from the surface of the leaves and 

 stems and that only 30% obtain it from feeding on squares and bolls. 



1928 - Eddy, C. O. Cotton flea hopper studies of 1927 and 1928. S.C. Agr. Expt. Sta. 

 B. 251, 18 p., 3 fig., 6 ref. Oct. Clemson. 



"In addition to control measures already noticed, a mixture of 2 lbs. sulfur 

 to 1 lb. calcium arsenate is recommended for use in fields infested with the boll 

 weevil ... as well as Psallus seriatus Reut." 



1928 - Hamner, A. L. Predicting serious cotton aphids infestation. J. Econ. Ent. 

 21(5):736-741. 



Serious infestations of the cotton aphids have occasionally followed appli- 

 cations of calcium arsenate against the boll weevil, and a rapid increase has been 



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